libgcc: Decrease size of _Unwind_FrameState and even more size of cleared area in uw_frame_state_for

The following patch implements something that has Florian found as
low hanging fruit in our unwinder and has been discussed in the
https://gcc.gnu.org/wiki/cauldron2022#cauldron2022talks.inprocess_unwinding_bof
talk.
_Unwind_FrameState type seems to be (unlike the pre-GCC 3 frame_state
which has been part of ABI) private to unwind-dw2.c + unwind.inc it
includes, it is always defined on the stack of some entrypoints, initialized
by static uw_frame_state_for and the address of it is also passed to other
static functions or the static inlines handling machine dependent unwinding,
but it isn't fortunately passed to any callbacks or public functions, so I
think we can safely change it any time we want.
Florian mentioned that the structure is large even on x86_64, 384 bytes
there, starts with 328 bytes long element with frame_state_reg_info type
which then starts with an array with __LIBGCC_DWARF_FRAME_REGISTERS__ + 1
elements, each of them is 16 bytes long, on x86_64
__LIBGCC_DWARF_FRAME_REGISTERS__ is just 17 but even that is big, on say
riscv __LIBGCC_DWARF_FRAME_REGISTERS__ is I think 128, on powerpc 111,
on sh 153 etc.  And, we memset to zero the whole fs variable with the
_Unwind_FrameState type at the start of the unwinding.
The reason why each element is 16 byte (on 64-bit arches) is that it
contains some pointer or pointer sized integer and then an enum (with just
7 different enumerators) + padding.

The following patch decreases it by moving the enum into a separate
array and using just one byte for each register in that second array.
We could compress it even more, say 4 bits per register, but I don't
want to uglify the code for it too much and make the accesses slower.
Furthermore, the clearing of the object can clear only thos how array
and members after it, because REG_UNSAVED enumerator (0) doesn't actually
need any pointer or pointer sized integer, it is just the other kinds
that need to have there something.
By doing this, on x86_64 the above numbers change to _Unwind_FrameState
type being now 264 bytes long, frame_state_reg_info 208 bytes and we
don't clear the first 144 bytes of the object, so the memset is 120 bytes,
so ~ 31% of the old clearing size.  On riscv 64-bit assuming it has same
structure layout rules for the few types used there that would be
~ 2160 bytes of _Unwind_FrameState type before and ~ 1264 bytes after,
with the memset previously ~ 2160 bytes and after ~ 232 bytes after.

We've also talked about possibly adding a number of initially initialized
regs and initializing the rest lazily, but at least for x86_64 with
18 elements in the array that doesn't seem to be worth it anymore,
especially because return address column is 16 there and that is usually the
first thing to be touched.  It might theory help with lots of registers if
they are usually untouched, but would uglify and complicate any stores to
how by having to check there for the not initialized yet cases and lazy
initialization, and similarly for all reads of how to do there if below
last initialized one, use how, otherwise imply REG_UNSAVED.

The disadvantage of the patch is that touching reg[x].loc and how[x]
now means 2 cachelines rather than one as before, and I admit beyond
bootstrap/regtest I haven't benchmarked it in any way.

2022-10-06  Jakub Jelinek  <jakub@redhat.com>

	* unwind-dw2.h (REG_UNSAVED, REG_SAVED_OFFSET, REG_SAVED_REG,
	REG_SAVED_EXP, REG_SAVED_VAL_OFFSET, REG_SAVED_VAL_EXP,
	REG_UNDEFINED): New anonymous enum, moved from inside of
	struct frame_state_reg_info.
	(struct frame_state_reg_info): Remove reg[].how element and the
	anonymous enum there.  Add how element.
	* unwind-dw2.c: Include stddef.h.
	(uw_frame_state_for): Don't clear first
	offsetof (_Unwind_FrameState, regs.how[0]) bytes of *fs.
	(execute_cfa_program, __frame_state_for, uw_update_context_1,
	uw_update_context): Use fs->regs.how[X] instead of fs->regs.reg[X].how
	or fs.regs.how[X] instead of fs.regs.reg[X].how.
	* config/sh/linux-unwind.h (sh_fallback_frame_state): Likewise.
	* config/bfin/linux-unwind.h (bfin_fallback_frame_state): Likewise.
	* config/pa/linux-unwind.h (pa32_fallback_frame_state): Likewise.
	* config/pa/hpux-unwind.h (UPDATE_FS_FOR_SAR, UPDATE_FS_FOR_GR,
	UPDATE_FS_FOR_FR, UPDATE_FS_FOR_PC, pa_fallback_frame_state):
	Likewise.
	* config/alpha/vms-unwind.h (alpha_vms_fallback_frame_state):
	Likewise.
	* config/alpha/linux-unwind.h (alpha_fallback_frame_state): Likewise.
	* config/arc/linux-unwind.h (arc_fallback_frame_state,
	arc_frob_update_context): Likewise.
	* config/riscv/linux-unwind.h (riscv_fallback_frame_state): Likewise.
	* config/nios2/linux-unwind.h (NIOS2_REG): Likewise.
	* config/nds32/linux-unwind.h (NDS32_PUT_FS_REG): Likewise.
	* config/s390/tpf-unwind.h (s390_fallback_frame_state): Likewise.
	* config/s390/linux-unwind.h (s390_fallback_frame_state): Likewise.
	* config/sparc/sol2-unwind.h (sparc64_frob_update_context,
	MD_FALLBACK_FRAME_STATE_FOR): Likewise.
	* config/sparc/linux-unwind.h (sparc64_fallback_frame_state,
	sparc64_frob_update_context, sparc_fallback_frame_state): Likewise.
	* config/i386/sol2-unwind.h (x86_64_fallback_frame_state,
	x86_fallback_frame_state): Likewise.
	* config/i386/w32-unwind.h (i386_w32_fallback_frame_state): Likewise.
	* config/i386/linux-unwind.h (x86_64_fallback_frame_state,
	x86_fallback_frame_state): Likewise.
	* config/i386/freebsd-unwind.h (x86_64_freebsd_fallback_frame_state):
	Likewise.
	* config/i386/dragonfly-unwind.h
	(x86_64_dragonfly_fallback_frame_state): Likewise.
	* config/i386/gnu-unwind.h (x86_gnu_fallback_frame_state): Likewise.
	* config/csky/linux-unwind.h (csky_fallback_frame_state): Likewise.
	* config/aarch64/linux-unwind.h (aarch64_fallback_frame_state):
	Likewise.
	* config/aarch64/freebsd-unwind.h
	(aarch64_freebsd_fallback_frame_state): Likewise.
	* config/aarch64/aarch64-unwind.h (aarch64_frob_update_context):
	Likewise.
	* config/or1k/linux-unwind.h (or1k_fallback_frame_state): Likewise.
	* config/mips/linux-unwind.h (mips_fallback_frame_state): Likewise.
	* config/loongarch/linux-unwind.h (loongarch_fallback_frame_state):
	Likewise.
	* config/m68k/linux-unwind.h (m68k_fallback_frame_state): Likewise.
	* config/xtensa/linux-unwind.h (xtensa_fallback_frame_state):
	Likewise.
	* config/rs6000/darwin-fallback.c (set_offset): Likewise.
	* config/rs6000/aix-unwind.h (MD_FROB_UPDATE_CONTEXT): Likewise.
	* config/rs6000/linux-unwind.h (ppc_fallback_frame_state): Likewise.
	* config/rs6000/freebsd-unwind.h (frob_update_context): Likewise.

35 files changed, 296 insertions, 292 deletions

diff --git a/libgcc/config/aarch64/aarch64-unwind.h b/libgcc/config/aarch64/aarch64-unwind.h
index e082e95..26db9cb 100644
--- a/libgcc/config/aarch64/aarch64-unwind.h
+++ b/libgcc/config/aarch64/aarch64-unwind.h
@@ -80,7 +80,7 @@ aarch64_frob_update_context (struct _Unwind_Context *context,
 {
   const int reg = DWARF_REGNUM_AARCH64_RA_STATE;
   int ra_signed;
-  if (fs->regs.reg[reg].how == REG_UNSAVED)
+  if (fs->regs.how[reg] == REG_UNSAVED)
     ra_signed = fs->regs.reg[reg].loc.offset & 0x1;
   else
     ra_signed = _Unwind_GetGR (context, reg) & 0x1;
diff --git a/libgcc/config/aarch64/freebsd-unwind.h b/libgcc/config/aarch64/freebsd-unwind.h
index 8d64680..2f795fb 100644
--- a/libgcc/config/aarch64/freebsd-unwind.h
+++ b/libgcc/config/aarch64/freebsd-unwind.h
@@ -90,7 +90,7 @@ aarch64_freebsd_fallback_frame_state
   fs->regs.cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
 
   for (n = 0; n < 32; n++)
-    fs->regs.reg[n].how = REG_SAVED_OFFSET;
+    fs->regs.how[n] = REG_SAVED_OFFSET;
 
   for (n = 0; n < 30; n++)
     fs->regs.reg[n].loc.offset = (_Unwind_Ptr) &(sc->XREG(n)) - new_cfa;
@@ -98,7 +98,7 @@ aarch64_freebsd_fallback_frame_state
   fs->regs.reg[30].loc.offset = (_Unwind_Ptr) &(sc->REG_NAME(lr)) - new_cfa;
   fs->regs.reg[31].loc.offset = (_Unwind_Ptr) &(sc->REG_NAME(sp)) - new_cfa;
 
-  fs->regs.reg[DARC].how = REG_SAVED_OFFSET;
+  fs->regs.how[DARC] = REG_SAVED_OFFSET;
   fs->regs.reg[DARC].loc.offset = (_Unwind_Ptr) &(sc->REG_NAME(elr)) - new_cfa;
 
   fs->retaddr_column = DARC;
diff --git a/libgcc/config/aarch64/linux-unwind.h b/libgcc/config/aarch64/linux-unwind.h
index 551b489..bce3f3c 100644
--- a/libgcc/config/aarch64/linux-unwind.h
+++ b/libgcc/config/aarch64/linux-unwind.h
@@ -89,7 +89,7 @@ aarch64_fallback_frame_state (struct _Unwind_Context *context,
 
   for (i = 0; i < AARCH64_DWARF_NUMBER_R; i++)
     {
-      fs->regs.reg[AARCH64_DWARF_R0 + i].how = REG_SAVED_OFFSET;
+      fs->regs.how[AARCH64_DWARF_R0 + i] = REG_SAVED_OFFSET;
       fs->regs.reg[AARCH64_DWARF_R0 + i].loc.offset =
 	(_Unwind_Ptr) & (sc->regs[i]) - new_cfa;
     }
@@ -115,7 +115,7 @@ aarch64_fallback_frame_state (struct _Unwind_Context *context,
 	    {
 	      _Unwind_Sword offset;
 
-	      fs->regs.reg[AARCH64_DWARF_V0 + i].how = REG_SAVED_OFFSET;
+	      fs->regs.how[AARCH64_DWARF_V0 + i] = REG_SAVED_OFFSET;
 
 	      /* sigcontext contains 32 128bit registers for V0 to
 		 V31.  The kernel will have saved the contents of the
@@ -142,12 +142,12 @@ aarch64_fallback_frame_state (struct _Unwind_Context *context,
 	}
     }
 
-  fs->regs.reg[31].how = REG_SAVED_OFFSET;
+  fs->regs.how[31] = REG_SAVED_OFFSET;
   fs->regs.reg[31].loc.offset = (_Unwind_Ptr) & (sc->sp) - new_cfa;
 
   fs->signal_frame = 1;
 
-  fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].how =
+  fs->regs.how[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__] =
     REG_SAVED_VAL_OFFSET;
   fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].loc.offset =
     (_Unwind_Ptr) (sc->pc) - new_cfa;
diff --git a/libgcc/config/alpha/linux-unwind.h b/libgcc/config/alpha/linux-unwind.h
index 1f7f95e..1a3a69d 100644
--- a/libgcc/config/alpha/linux-unwind.h
+++ b/libgcc/config/alpha/linux-unwind.h
@@ -67,17 +67,17 @@ alpha_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
   for (i = 0; i < 30; ++i)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset
 	= (long) &sc->sc_regs[i] - new_cfa;
     }
   for (i = 0; i < 31; ++i)
     {
-      fs->regs.reg[i+32].how = REG_SAVED_OFFSET;
+      fs->regs.how[i+32] = REG_SAVED_OFFSET;
       fs->regs.reg[i+32].loc.offset
 	= (long) &sc->sc_fpregs[i] - new_cfa;
     }
-  fs->regs.reg[64].how = REG_SAVED_OFFSET;
+  fs->regs.how[64] = REG_SAVED_OFFSET;
   fs->regs.reg[64].loc.offset = (long)&sc->sc_pc - new_cfa;
   fs->retaddr_column = 64;
   fs->signal_frame = 1;
diff --git a/libgcc/config/alpha/vms-unwind.h b/libgcc/config/alpha/vms-unwind.h
index 5219d8e..71b59a6 100644
--- a/libgcc/config/alpha/vms-unwind.h
+++ b/libgcc/config/alpha/vms-unwind.h
@@ -50,7 +50,7 @@ extern int SYS$GL_CALL_HANDL;
 
 #define UPDATE_FS_FOR_CFA_GR(FS, GRN, LOC, CFA) \
 do { \
-(FS)->regs.reg[GRN].how = REG_SAVED_OFFSET;      \
+(FS)->regs.how[GRN] = REG_SAVED_OFFSET;      \
 (FS)->regs.reg[GRN].loc.offset = (_Unwind_Sword) ((REG) (LOC) - (REG) (CFA)); \
 } while (0);
 
@@ -212,10 +212,10 @@ alpha_vms_fallback_frame_state (struct _Unwind_Context *context,
 	if (eh_debug)
 	  printf ("FALLBACK: REGISTER frame procedure\n");
 
-	fs->regs.reg[RA_COLUMN].how = REG_SAVED_REG;
+	fs->regs.how[RA_COLUMN] = REG_SAVED_REG;
 	fs->regs.reg[RA_COLUMN].loc.reg = pv->pdsc$b_save_ra;
 	
-	fs->regs.reg[29].how = REG_SAVED_REG;
+	fs->regs.how[29] = REG_SAVED_REG;
 	fs->regs.reg[29].loc.reg = pv->pdsc$b_save_fp;
 	
 	break;
diff --git a/libgcc/config/arc/linux-unwind.h b/libgcc/config/arc/linux-unwind.h
index be42a31..231971a 100644
--- a/libgcc/config/arc/linux-unwind.h
+++ b/libgcc/config/arc/linux-unwind.h
@@ -122,7 +122,7 @@ arc_fallback_frame_state (struct _Unwind_Context *context,
 
   fs->signal_frame = 1;
   fs->retaddr_column = __LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__;
-  fs->regs.reg[fs->retaddr_column].how = REG_SAVED_VAL_OFFSET;
+  fs->regs.how[fs->retaddr_column] = REG_SAVED_VAL_OFFSET;
   fs->regs.reg[fs->retaddr_column].loc.offset =
     ((_Unwind_Ptr) (regs[ret])) - new_cfa;
 
@@ -140,7 +140,7 @@ arc_frob_update_context (struct _Unwind_Context *context,
   _Unwind_Word fp_val;
   asm ("mov %0,fp" : "=r" (fp_val));
 
-  switch (fs->regs.reg[27].how)
+  switch (fs->regs.how[27])
     {
     case REG_UNSAVED:
     case REG_UNDEFINED:
diff --git a/libgcc/config/bfin/linux-unwind.h b/libgcc/config/bfin/linux-unwind.h
index 34ab7da..de7e321 100644
--- a/libgcc/config/bfin/linux-unwind.h
+++ b/libgcc/config/bfin/linux-unwind.h
@@ -68,93 +68,93 @@ bfin_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_reg = 14;
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)&sc->sc_r0 - new_cfa;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (long)&sc->sc_r1 - new_cfa;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long)&sc->sc_r2 - new_cfa;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (long)&sc->sc_r3 - new_cfa;
-  fs->regs.reg[4].how = REG_SAVED_OFFSET;
+  fs->regs.how[4] = REG_SAVED_OFFSET;
   fs->regs.reg[4].loc.offset = (long)&sc->sc_r4 - new_cfa;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
   fs->regs.reg[5].loc.offset = (long)&sc->sc_r5 - new_cfa;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
   fs->regs.reg[6].loc.offset = (long)&sc->sc_r6 - new_cfa;
-  fs->regs.reg[7].how = REG_SAVED_OFFSET;
+  fs->regs.how[7] = REG_SAVED_OFFSET;
   fs->regs.reg[7].loc.offset = (long)&sc->sc_r7 - new_cfa;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
   fs->regs.reg[8].loc.offset = (long)&sc->sc_p0 - new_cfa;
-  fs->regs.reg[9].how = REG_SAVED_OFFSET;
+  fs->regs.how[9] = REG_SAVED_OFFSET;
   fs->regs.reg[9].loc.offset = (long)&sc->sc_p1 - new_cfa;
-  fs->regs.reg[10].how = REG_SAVED_OFFSET;
+  fs->regs.how[10] = REG_SAVED_OFFSET;
   fs->regs.reg[10].loc.offset = (long)&sc->sc_p2 - new_cfa;
-  fs->regs.reg[11].how = REG_SAVED_OFFSET;
+  fs->regs.how[11] = REG_SAVED_OFFSET;
   fs->regs.reg[11].loc.offset = (long)&sc->sc_p3 - new_cfa;
-  fs->regs.reg[12].how = REG_SAVED_OFFSET;
+  fs->regs.how[12] = REG_SAVED_OFFSET;
   fs->regs.reg[12].loc.offset = (long)&sc->sc_p4 - new_cfa;
-  fs->regs.reg[13].how = REG_SAVED_OFFSET;
+  fs->regs.how[13] = REG_SAVED_OFFSET;
   fs->regs.reg[13].loc.offset = (long)&sc->sc_p5 - new_cfa;
 
-  fs->regs.reg[15].how = REG_SAVED_OFFSET;
+  fs->regs.how[15] = REG_SAVED_OFFSET;
   fs->regs.reg[15].loc.offset = (long)&sc->sc_fp - new_cfa;
-  fs->regs.reg[16].how = REG_SAVED_OFFSET;
+  fs->regs.how[16] = REG_SAVED_OFFSET;
   fs->regs.reg[16].loc.offset = (long)&sc->sc_i0 - new_cfa;
-  fs->regs.reg[17].how = REG_SAVED_OFFSET;
+  fs->regs.how[17] = REG_SAVED_OFFSET;
   fs->regs.reg[17].loc.offset = (long)&sc->sc_i1 - new_cfa;
-  fs->regs.reg[18].how = REG_SAVED_OFFSET;
+  fs->regs.how[18] = REG_SAVED_OFFSET;
   fs->regs.reg[18].loc.offset = (long)&sc->sc_i2 - new_cfa;
-  fs->regs.reg[19].how = REG_SAVED_OFFSET;
+  fs->regs.how[19] = REG_SAVED_OFFSET;
   fs->regs.reg[19].loc.offset = (long)&sc->sc_i3 - new_cfa;
-  fs->regs.reg[20].how = REG_SAVED_OFFSET;
+  fs->regs.how[20] = REG_SAVED_OFFSET;
   fs->regs.reg[20].loc.offset = (long)&sc->sc_b0 - new_cfa;
-  fs->regs.reg[21].how = REG_SAVED_OFFSET;
+  fs->regs.how[21] = REG_SAVED_OFFSET;
   fs->regs.reg[21].loc.offset = (long)&sc->sc_b1 - new_cfa;
-  fs->regs.reg[22].how = REG_SAVED_OFFSET;
+  fs->regs.how[22] = REG_SAVED_OFFSET;
   fs->regs.reg[22].loc.offset = (long)&sc->sc_b2 - new_cfa;
-  fs->regs.reg[23].how = REG_SAVED_OFFSET;
+  fs->regs.how[23] = REG_SAVED_OFFSET;
   fs->regs.reg[23].loc.offset = (long)&sc->sc_b3 - new_cfa;
-  fs->regs.reg[24].how = REG_SAVED_OFFSET;
+  fs->regs.how[24] = REG_SAVED_OFFSET;
   fs->regs.reg[24].loc.offset = (long)&sc->sc_l0 - new_cfa;
-  fs->regs.reg[25].how = REG_SAVED_OFFSET;
+  fs->regs.how[25] = REG_SAVED_OFFSET;
   fs->regs.reg[25].loc.offset = (long)&sc->sc_l1 - new_cfa;
-  fs->regs.reg[26].how = REG_SAVED_OFFSET;
+  fs->regs.how[26] = REG_SAVED_OFFSET;
   fs->regs.reg[26].loc.offset = (long)&sc->sc_l2 - new_cfa;
-  fs->regs.reg[27].how = REG_SAVED_OFFSET;
+  fs->regs.how[27] = REG_SAVED_OFFSET;
   fs->regs.reg[27].loc.offset = (long)&sc->sc_l3 - new_cfa;
-  fs->regs.reg[28].how = REG_SAVED_OFFSET;
+  fs->regs.how[28] = REG_SAVED_OFFSET;
   fs->regs.reg[28].loc.offset = (long)&sc->sc_m0 - new_cfa;
-  fs->regs.reg[29].how = REG_SAVED_OFFSET;
+  fs->regs.how[29] = REG_SAVED_OFFSET;
   fs->regs.reg[29].loc.offset = (long)&sc->sc_m1 - new_cfa;
-  fs->regs.reg[30].how = REG_SAVED_OFFSET;
+  fs->regs.how[30] = REG_SAVED_OFFSET;
   fs->regs.reg[30].loc.offset = (long)&sc->sc_m2 - new_cfa;
-  fs->regs.reg[31].how = REG_SAVED_OFFSET;
+  fs->regs.how[31] = REG_SAVED_OFFSET;
   fs->regs.reg[31].loc.offset = (long)&sc->sc_m3 - new_cfa;
   /* FIXME: Handle A0, A1, CC.  */
-  fs->regs.reg[35].how = REG_SAVED_OFFSET;
+  fs->regs.how[35] = REG_SAVED_OFFSET;
   fs->regs.reg[35].loc.offset = (long)&sc->sc_rets - new_cfa;
-  fs->regs.reg[36].how = REG_SAVED_OFFSET;
+  fs->regs.how[36] = REG_SAVED_OFFSET;
   fs->regs.reg[36].loc.offset = (long)&sc->sc_pc - new_cfa;
-  fs->regs.reg[37].how = REG_SAVED_OFFSET;
+  fs->regs.how[37] = REG_SAVED_OFFSET;
   fs->regs.reg[37].loc.offset = (long)&sc->sc_retx - new_cfa;
 
-  fs->regs.reg[40].how = REG_SAVED_OFFSET;
+  fs->regs.how[40] = REG_SAVED_OFFSET;
   fs->regs.reg[40].loc.offset = (long)&sc->sc_astat - new_cfa;
-  fs->regs.reg[41].how = REG_SAVED_OFFSET;
+  fs->regs.how[41] = REG_SAVED_OFFSET;
   fs->regs.reg[41].loc.offset = (long)&sc->sc_seqstat - new_cfa;
 
-  fs->regs.reg[44].how = REG_SAVED_OFFSET;
+  fs->regs.how[44] = REG_SAVED_OFFSET;
   fs->regs.reg[44].loc.offset = (long)&sc->sc_lt0 - new_cfa;
-  fs->regs.reg[45].how = REG_SAVED_OFFSET;
+  fs->regs.how[45] = REG_SAVED_OFFSET;
   fs->regs.reg[45].loc.offset = (long)&sc->sc_lt1 - new_cfa;
-  fs->regs.reg[46].how = REG_SAVED_OFFSET;
+  fs->regs.how[46] = REG_SAVED_OFFSET;
   fs->regs.reg[46].loc.offset = (long)&sc->sc_lc0 - new_cfa;
-  fs->regs.reg[47].how = REG_SAVED_OFFSET;
+  fs->regs.how[47] = REG_SAVED_OFFSET;
   fs->regs.reg[47].loc.offset = (long)&sc->sc_lc1 - new_cfa;
-  fs->regs.reg[48].how = REG_SAVED_OFFSET;
+  fs->regs.how[48] = REG_SAVED_OFFSET;
   fs->regs.reg[48].loc.offset = (long)&sc->sc_lb0 - new_cfa;
-  fs->regs.reg[49].how = REG_SAVED_OFFSET;
+  fs->regs.how[49] = REG_SAVED_OFFSET;
   fs->regs.reg[49].loc.offset = (long)&sc->sc_lb1 - new_cfa;
   fs->retaddr_column = 35;
 
diff --git a/libgcc/config/csky/linux-unwind.h b/libgcc/config/csky/linux-unwind.h
index a2e4a6d..bdc8f2e 100644
--- a/libgcc/config/csky/linux-unwind.h
+++ b/libgcc/config/csky/linux-unwind.h
@@ -85,28 +85,28 @@ csky_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_reg = STACK_POINTER_REGNUM;
   fs->regs.cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
 
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (_Unwind_Ptr) & sc_pt_regs (a0) - new_cfa;
 
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (_Unwind_Ptr) & sc_pt_regs (a1) - new_cfa;
 
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (_Unwind_Ptr) & sc_pt_regs (a2) - new_cfa;
 
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (_Unwind_Ptr) & sc_pt_regs (a3) - new_cfa;
 
   for (i = 4; i < 14; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset =
 	(_Unwind_Ptr) & sc_pt_regs (regs[i - 4]) - new_cfa;
     }
 
   for (i = 16; i < 31; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset =
 	(_Unwind_Ptr) & sc_pt_regs (exregs[i - 16]) - new_cfa;
     }
@@ -114,10 +114,10 @@ csky_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.reg[31].loc.offset =
     (_Unwind_Ptr) & sc_pt_regs_tls (tls) - new_cfa;
   /* FIXME : hi lo ? */
-  fs->regs.reg[15].how = REG_SAVED_OFFSET;
+  fs->regs.how[15] = REG_SAVED_OFFSET;
   fs->regs.reg[15].loc.offset = (_Unwind_Ptr) & sc_pt_regs_lr - new_cfa;
 
-  fs->regs.reg[32].how = REG_SAVED_OFFSET;
+  fs->regs.how[32] = REG_SAVED_OFFSET;
   fs->regs.reg[32].loc.offset = (_Unwind_Ptr) & sc_pt_regs (pc) - new_cfa;
   fs->retaddr_column = 32;
   fs->signal_frame = 1;
diff --git a/libgcc/config/i386/dragonfly-unwind.h b/libgcc/config/i386/dragonfly-unwind.h
index de3e230..4cafc5c 100644
--- a/libgcc/config/i386/dragonfly-unwind.h
+++ b/libgcc/config/i386/dragonfly-unwind.h
@@ -102,37 +102,37 @@ x86_64_dragonfly_fallback_frame_state
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
   /* The SVR4 register numbering macros aren't usable in libgcc.  */
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)&sf->REG_NAME(rax) - new_cfa;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (long)&sf->REG_NAME(rdx) - new_cfa;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long)&sf->REG_NAME(rcx) - new_cfa;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (long)&sf->REG_NAME(rbx) - new_cfa;
-  fs->regs.reg[4].how = REG_SAVED_OFFSET;
+  fs->regs.how[4] = REG_SAVED_OFFSET;
   fs->regs.reg[4].loc.offset = (long)&sf->REG_NAME(rsi) - new_cfa;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
   fs->regs.reg[5].loc.offset = (long)&sf->REG_NAME(rdi) - new_cfa;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
   fs->regs.reg[6].loc.offset = (long)&sf->REG_NAME(rbp) - new_cfa;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
   fs->regs.reg[8].loc.offset = (long)&sf->REG_NAME(r8) - new_cfa;
-  fs->regs.reg[9].how = REG_SAVED_OFFSET;
+  fs->regs.how[9] = REG_SAVED_OFFSET;
   fs->regs.reg[9].loc.offset = (long)&sf->REG_NAME(r9) - new_cfa;
-  fs->regs.reg[10].how = REG_SAVED_OFFSET;
+  fs->regs.how[10] = REG_SAVED_OFFSET;
   fs->regs.reg[10].loc.offset = (long)&sf->REG_NAME(r10) - new_cfa;
-  fs->regs.reg[11].how = REG_SAVED_OFFSET;
+  fs->regs.how[11] = REG_SAVED_OFFSET;
   fs->regs.reg[11].loc.offset = (long)&sf->REG_NAME(r11) - new_cfa;
-  fs->regs.reg[12].how = REG_SAVED_OFFSET;
+  fs->regs.how[12] = REG_SAVED_OFFSET;
   fs->regs.reg[12].loc.offset = (long)&sf->REG_NAME(r12) - new_cfa;
-  fs->regs.reg[13].how = REG_SAVED_OFFSET;
+  fs->regs.how[13] = REG_SAVED_OFFSET;
   fs->regs.reg[13].loc.offset = (long)&sf->REG_NAME(r13) - new_cfa;
-  fs->regs.reg[14].how = REG_SAVED_OFFSET;
+  fs->regs.how[14] = REG_SAVED_OFFSET;
   fs->regs.reg[14].loc.offset = (long)&sf->REG_NAME(r14) - new_cfa;
-  fs->regs.reg[15].how = REG_SAVED_OFFSET;
+  fs->regs.how[15] = REG_SAVED_OFFSET;
   fs->regs.reg[15].loc.offset = (long)&sf->REG_NAME(r15) - new_cfa;
-  fs->regs.reg[16].how = REG_SAVED_OFFSET;
+  fs->regs.how[16] = REG_SAVED_OFFSET;
   fs->regs.reg[16].loc.offset = (long)&sf->REG_NAME(rip) - new_cfa;
   fs->retaddr_column = 16;
   fs->signal_frame = 1;
@@ -182,21 +182,21 @@ x86_dragonfly_fallback_frame_state
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
   /* The SVR4 register numbering macros aren't usable in libgcc.  */
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)&sf->REG_NAME(eax) - new_cfa;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (long)&sf->REG_NAME(ebx) - new_cfa;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (long)&sf->REG_NAME(ecx) - new_cfa;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long)&sf->REG_NAME(edx) - new_cfa;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
   fs->regs.reg[6].loc.offset = (long)&sf->REG_NAME(esi) - new_cfa;
-  fs->regs.reg[7].how = REG_SAVED_OFFSET;
+  fs->regs.how[7] = REG_SAVED_OFFSET;
   fs->regs.reg[7].loc.offset = (long)&sf->REG_NAME(edi) - new_cfa;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
   fs->regs.reg[5].loc.offset = (long)&sf->REG_NAME(ebp) - new_cfa;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
   fs->regs.reg[8].loc.offset = (long)&sf->REG_NAME(eip) - new_cfa;
   fs->retaddr_column = 8;
   fs->signal_frame = 1;
diff --git a/libgcc/config/i386/freebsd-unwind.h b/libgcc/config/i386/freebsd-unwind.h
index 777fda8..dcbd8cd 100644
--- a/libgcc/config/i386/freebsd-unwind.h
+++ b/libgcc/config/i386/freebsd-unwind.h
@@ -110,37 +110,37 @@ x86_64_freebsd_fallback_frame_state
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
   /* The SVR4 register numbering macros aren't usable in libgcc.  */
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)&sf->REG_NAME(rax) - new_cfa;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (long)&sf->REG_NAME(rdx) - new_cfa;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long)&sf->REG_NAME(rcx) - new_cfa;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (long)&sf->REG_NAME(rbx) - new_cfa;
-  fs->regs.reg[4].how = REG_SAVED_OFFSET;
+  fs->regs.how[4] = REG_SAVED_OFFSET;
   fs->regs.reg[4].loc.offset = (long)&sf->REG_NAME(rsi) - new_cfa;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
   fs->regs.reg[5].loc.offset = (long)&sf->REG_NAME(rdi) - new_cfa;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
   fs->regs.reg[6].loc.offset = (long)&sf->REG_NAME(rbp) - new_cfa;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
   fs->regs.reg[8].loc.offset = (long)&sf->REG_NAME(r8) - new_cfa;
-  fs->regs.reg[9].how = REG_SAVED_OFFSET;
+  fs->regs.how[9] = REG_SAVED_OFFSET;
   fs->regs.reg[9].loc.offset = (long)&sf->REG_NAME(r9) - new_cfa;
-  fs->regs.reg[10].how = REG_SAVED_OFFSET;
+  fs->regs.how[10] = REG_SAVED_OFFSET;
   fs->regs.reg[10].loc.offset = (long)&sf->REG_NAME(r10) - new_cfa;
-  fs->regs.reg[11].how = REG_SAVED_OFFSET;
+  fs->regs.how[11] = REG_SAVED_OFFSET;
   fs->regs.reg[11].loc.offset = (long)&sf->REG_NAME(r11) - new_cfa;
-  fs->regs.reg[12].how = REG_SAVED_OFFSET;
+  fs->regs.how[12] = REG_SAVED_OFFSET;
   fs->regs.reg[12].loc.offset = (long)&sf->REG_NAME(r12) - new_cfa;
-  fs->regs.reg[13].how = REG_SAVED_OFFSET;
+  fs->regs.how[13] = REG_SAVED_OFFSET;
   fs->regs.reg[13].loc.offset = (long)&sf->REG_NAME(r13) - new_cfa;
-  fs->regs.reg[14].how = REG_SAVED_OFFSET;
+  fs->regs.how[14] = REG_SAVED_OFFSET;
   fs->regs.reg[14].loc.offset = (long)&sf->REG_NAME(r14) - new_cfa;
-  fs->regs.reg[15].how = REG_SAVED_OFFSET;
+  fs->regs.how[15] = REG_SAVED_OFFSET;
   fs->regs.reg[15].loc.offset = (long)&sf->REG_NAME(r15) - new_cfa;
-  fs->regs.reg[16].how = REG_SAVED_OFFSET;
+  fs->regs.how[16] = REG_SAVED_OFFSET;
   fs->regs.reg[16].loc.offset = (long)&sf->REG_NAME(rip) - new_cfa;
   fs->retaddr_column = 16;
   fs->signal_frame = 1;
@@ -189,21 +189,21 @@ x86_freebsd_fallback_frame_state
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
   /* The SVR4 register numbering macros aren't usable in libgcc.  */
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)&sf->REG_NAME(eax) - new_cfa;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (long)&sf->REG_NAME(ebx) - new_cfa;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (long)&sf->REG_NAME(ecx) - new_cfa;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long)&sf->REG_NAME(edx) - new_cfa;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
   fs->regs.reg[6].loc.offset = (long)&sf->REG_NAME(esi) - new_cfa;
-  fs->regs.reg[7].how = REG_SAVED_OFFSET;
+  fs->regs.how[7] = REG_SAVED_OFFSET;
   fs->regs.reg[7].loc.offset = (long)&sf->REG_NAME(edi) - new_cfa;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
   fs->regs.reg[5].loc.offset = (long)&sf->REG_NAME(ebp) - new_cfa;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
   fs->regs.reg[8].loc.offset = (long)&sf->REG_NAME(eip) - new_cfa;
   fs->retaddr_column = 8;
   fs->signal_frame = 1;
diff --git a/libgcc/config/i386/gnu-unwind.h b/libgcc/config/i386/gnu-unwind.h
index 48fbff8..25eb690 100644
--- a/libgcc/config/i386/gnu-unwind.h
+++ b/libgcc/config/i386/gnu-unwind.h
@@ -123,14 +123,14 @@ x86_gnu_fallback_frame_state
   fs->regs.cfa_reg = 4;
   fs->regs.cfa_offset = usp - (unsigned long) context->cfa;
 
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
-  fs->regs.reg[7].how = REG_SAVED_OFFSET;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
+  fs->regs.how[7] = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
 
   fs->retaddr_column = 8;
   fs->signal_frame = 1;
diff --git a/libgcc/config/i386/linux-unwind.h b/libgcc/config/i386/linux-unwind.h
index 7a9e4dc..48262b0 100644
--- a/libgcc/config/i386/linux-unwind.h
+++ b/libgcc/config/i386/linux-unwind.h
@@ -79,37 +79,37 @@ x86_64_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
   /* The SVR4 register numbering macros aren't usable in libgcc.  */
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)&sc->rax - new_cfa;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (long)&sc->rdx - new_cfa;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long)&sc->rcx - new_cfa;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (long)&sc->rbx - new_cfa;
-  fs->regs.reg[4].how = REG_SAVED_OFFSET;
+  fs->regs.how[4] = REG_SAVED_OFFSET;
   fs->regs.reg[4].loc.offset = (long)&sc->rsi - new_cfa;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
   fs->regs.reg[5].loc.offset = (long)&sc->rdi - new_cfa;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
   fs->regs.reg[6].loc.offset = (long)&sc->rbp - new_cfa;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
   fs->regs.reg[8].loc.offset = (long)&sc->r8 - new_cfa;
-  fs->regs.reg[9].how = REG_SAVED_OFFSET;
+  fs->regs.how[9] = REG_SAVED_OFFSET;
   fs->regs.reg[9].loc.offset = (long)&sc->r9 - new_cfa;
-  fs->regs.reg[10].how = REG_SAVED_OFFSET;
+  fs->regs.how[10] = REG_SAVED_OFFSET;
   fs->regs.reg[10].loc.offset = (long)&sc->r10 - new_cfa;
-  fs->regs.reg[11].how = REG_SAVED_OFFSET;
+  fs->regs.how[11] = REG_SAVED_OFFSET;
   fs->regs.reg[11].loc.offset = (long)&sc->r11 - new_cfa;
-  fs->regs.reg[12].how = REG_SAVED_OFFSET;
+  fs->regs.how[12] = REG_SAVED_OFFSET;
   fs->regs.reg[12].loc.offset = (long)&sc->r12 - new_cfa;
-  fs->regs.reg[13].how = REG_SAVED_OFFSET;
+  fs->regs.how[13] = REG_SAVED_OFFSET;
   fs->regs.reg[13].loc.offset = (long)&sc->r13 - new_cfa;
-  fs->regs.reg[14].how = REG_SAVED_OFFSET;
+  fs->regs.how[14] = REG_SAVED_OFFSET;
   fs->regs.reg[14].loc.offset = (long)&sc->r14 - new_cfa;
-  fs->regs.reg[15].how = REG_SAVED_OFFSET;
+  fs->regs.how[15] = REG_SAVED_OFFSET;
   fs->regs.reg[15].loc.offset = (long)&sc->r15 - new_cfa;
-  fs->regs.reg[16].how = REG_SAVED_OFFSET;
+  fs->regs.how[16] = REG_SAVED_OFFSET;
   fs->regs.reg[16].loc.offset = (long)&sc->rip - new_cfa;
   fs->retaddr_column = 16;
   fs->signal_frame = 1;
@@ -159,21 +159,21 @@ x86_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
   /* The SVR4 register numbering macros aren't usable in libgcc.  */
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)&sc->eax - new_cfa;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (long)&sc->ebx - new_cfa;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (long)&sc->ecx - new_cfa;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long)&sc->edx - new_cfa;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
   fs->regs.reg[6].loc.offset = (long)&sc->esi - new_cfa;
-  fs->regs.reg[7].how = REG_SAVED_OFFSET;
+  fs->regs.how[7] = REG_SAVED_OFFSET;
   fs->regs.reg[7].loc.offset = (long)&sc->edi - new_cfa;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
   fs->regs.reg[5].loc.offset = (long)&sc->ebp - new_cfa;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
   fs->regs.reg[8].loc.offset = (long)&sc->eip - new_cfa;
   fs->retaddr_column = 8;
   fs->signal_frame = 1;
diff --git a/libgcc/config/i386/sol2-unwind.h b/libgcc/config/i386/sol2-unwind.h
index 08c9cd5..718dc35 100644
--- a/libgcc/config/i386/sol2-unwind.h
+++ b/libgcc/config/i386/sol2-unwind.h
@@ -94,37 +94,37 @@ x86_64_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
   /* The SVR4 register numbering macros aren't usable in libgcc.  */
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)&mctx->gregs[REG_RAX] - new_cfa;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (long)&mctx->gregs[REG_RDX] - new_cfa;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long)&mctx->gregs[REG_RCX] - new_cfa;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (long)&mctx->gregs[REG_RBX] - new_cfa;
-  fs->regs.reg[4].how = REG_SAVED_OFFSET;
+  fs->regs.how[4] = REG_SAVED_OFFSET;
   fs->regs.reg[4].loc.offset = (long)&mctx->gregs[REG_RSI] - new_cfa;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
   fs->regs.reg[5].loc.offset = (long)&mctx->gregs[REG_RDI] - new_cfa;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
   fs->regs.reg[6].loc.offset = (long)&mctx->gregs[REG_RBP] - new_cfa;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
   fs->regs.reg[8].loc.offset = (long)&mctx->gregs[REG_R8] - new_cfa;
-  fs->regs.reg[9].how = REG_SAVED_OFFSET;
+  fs->regs.how[9] = REG_SAVED_OFFSET;
   fs->regs.reg[9].loc.offset = (long)&mctx->gregs[REG_R9] - new_cfa;
-  fs->regs.reg[10].how = REG_SAVED_OFFSET;
+  fs->regs.how[10] = REG_SAVED_OFFSET;
   fs->regs.reg[10].loc.offset = (long)&mctx->gregs[REG_R10] - new_cfa;
-  fs->regs.reg[11].how = REG_SAVED_OFFSET;
+  fs->regs.how[11] = REG_SAVED_OFFSET;
   fs->regs.reg[11].loc.offset = (long)&mctx->gregs[REG_R11] - new_cfa;
-  fs->regs.reg[12].how = REG_SAVED_OFFSET;
+  fs->regs.how[12] = REG_SAVED_OFFSET;
   fs->regs.reg[12].loc.offset = (long)&mctx->gregs[REG_R12] - new_cfa;
-  fs->regs.reg[13].how = REG_SAVED_OFFSET;
+  fs->regs.how[13] = REG_SAVED_OFFSET;
   fs->regs.reg[13].loc.offset = (long)&mctx->gregs[REG_R13] - new_cfa;
-  fs->regs.reg[14].how = REG_SAVED_OFFSET;
+  fs->regs.how[14] = REG_SAVED_OFFSET;
   fs->regs.reg[14].loc.offset = (long)&mctx->gregs[REG_R14] - new_cfa;
-  fs->regs.reg[15].how = REG_SAVED_OFFSET;
+  fs->regs.how[15] = REG_SAVED_OFFSET;
   fs->regs.reg[15].loc.offset = (long)&mctx->gregs[REG_R15] - new_cfa;
-  fs->regs.reg[16].how = REG_SAVED_OFFSET;
+  fs->regs.how[16] = REG_SAVED_OFFSET;
   fs->regs.reg[16].loc.offset = (long)&mctx->gregs[REG_RIP] - new_cfa;
   fs->retaddr_column = 16;
   fs->signal_frame = 1;
@@ -180,21 +180,21 @@ x86_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
   /* The SVR4 register numbering macros aren't usable in libgcc.  */
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)&mctx->gregs[EAX] - new_cfa;
-  fs->regs.reg[3].how = REG_SAVED_OFFSET;
+  fs->regs.how[3] = REG_SAVED_OFFSET;
   fs->regs.reg[3].loc.offset = (long)&mctx->gregs[EBX] - new_cfa;
-  fs->regs.reg[1].how = REG_SAVED_OFFSET;
+  fs->regs.how[1] = REG_SAVED_OFFSET;
   fs->regs.reg[1].loc.offset = (long)&mctx->gregs[ECX] - new_cfa;
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long)&mctx->gregs[EDX] - new_cfa;
-  fs->regs.reg[6].how = REG_SAVED_OFFSET;
+  fs->regs.how[6] = REG_SAVED_OFFSET;
   fs->regs.reg[6].loc.offset = (long)&mctx->gregs[ESI] - new_cfa;
-  fs->regs.reg[7].how = REG_SAVED_OFFSET;
+  fs->regs.how[7] = REG_SAVED_OFFSET;
   fs->regs.reg[7].loc.offset = (long)&mctx->gregs[EDI] - new_cfa;
-  fs->regs.reg[5].how = REG_SAVED_OFFSET;
+  fs->regs.how[5] = REG_SAVED_OFFSET;
   fs->regs.reg[5].loc.offset = (long)&mctx->gregs[EBP] - new_cfa;
-  fs->regs.reg[8].how = REG_SAVED_OFFSET;
+  fs->regs.how[8] = REG_SAVED_OFFSET;
   fs->regs.reg[8].loc.offset = (long)&mctx->gregs[EIP] - new_cfa;
   fs->retaddr_column = 8;
 
diff --git a/libgcc/config/i386/w32-unwind.h b/libgcc/config/i386/w32-unwind.h
index 7c5980f..096e314 100644
--- a/libgcc/config/i386/w32-unwind.h
+++ b/libgcc/config/i386/w32-unwind.h
@@ -153,21 +153,21 @@ i386_w32_fallback_frame_state (struct _Unwind_Context *context,
       fs->regs.cfa_offset = new_cfa_ - (long) ctx_cfa_;
 
       /* Restore registers.  */
-      fs->regs.reg[0].how = REG_SAVED_OFFSET;
+      fs->regs.how[0] = REG_SAVED_OFFSET;
       fs->regs.reg[0].loc.offset = (long)&proc_ctx_->Eax - new_cfa_;
-      fs->regs.reg[3].how = REG_SAVED_OFFSET;
+      fs->regs.how[3] = REG_SAVED_OFFSET;
       fs->regs.reg[3].loc.offset = (long)&proc_ctx_->Ebx - new_cfa_;
-      fs->regs.reg[1].how = REG_SAVED_OFFSET;
+      fs->regs.how[1] = REG_SAVED_OFFSET;
       fs->regs.reg[1].loc.offset = (long)&proc_ctx_->Ecx - new_cfa_;
-      fs->regs.reg[2].how = REG_SAVED_OFFSET;
+      fs->regs.how[2] = REG_SAVED_OFFSET;
       fs->regs.reg[2].loc.offset = (long)&proc_ctx_->Edx - new_cfa_;
-      fs->regs.reg[6].how = REG_SAVED_OFFSET;
+      fs->regs.how[6] = REG_SAVED_OFFSET;
       fs->regs.reg[6].loc.offset = (long)&proc_ctx_->Esi - new_cfa_;
-      fs->regs.reg[7].how = REG_SAVED_OFFSET;
+      fs->regs.how[7] = REG_SAVED_OFFSET;
       fs->regs.reg[7].loc.offset = (long)&proc_ctx_->Edi - new_cfa_;
-      fs->regs.reg[5].how = REG_SAVED_OFFSET;
+      fs->regs.how[5] = REG_SAVED_OFFSET;
       fs->regs.reg[5].loc.offset = (long)&proc_ctx_->Ebp - new_cfa_;
-      fs->regs.reg[8].how = REG_SAVED_OFFSET;
+      fs->regs.how[8] = REG_SAVED_OFFSET;
       fs->regs.reg[8].loc.offset = (long)&proc_ctx_->Eip - new_cfa_;
       fs->retaddr_column = 8;
       fs->signal_frame = 1;
@@ -189,12 +189,12 @@ i386_w32_fallback_frame_state (struct _Unwind_Context *context,
       fs->regs.cfa_offset = new_cfa_ - (long) ctx_cfa_;
 
       /* The saved value of %ecx is at CFA - 4 */
-      fs->regs.reg[1].how = REG_SAVED_OFFSET;
+      fs->regs.how[1] = REG_SAVED_OFFSET;
       fs->regs.reg[1].loc.offset = -4;
 
       /* and what is stored at the CFA is the return address.  */
       fs->retaddr_column = 8;
-      fs->regs.reg[8].how = REG_SAVED_OFFSET;
+      fs->regs.how[8] = REG_SAVED_OFFSET;
       fs->regs.reg[8].loc.offset = 0;
       fs->signal_frame = 1;
 
diff --git a/libgcc/config/loongarch/linux-unwind.h b/libgcc/config/loongarch/linux-unwind.h
index 89c168c..f6c782f 100644
--- a/libgcc/config/loongarch/linux-unwind.h
+++ b/libgcc/config/loongarch/linux-unwind.h
@@ -64,12 +64,12 @@ loongarch_fallback_frame_state (struct _Unwind_Context *context,
 
   for (i = 0; i < 32; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset = (_Unwind_Ptr) & (sc->sc_regs[i]) - new_cfa;
     }
 
   fs->signal_frame = 1;
-  fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].how
+  fs->regs.how[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__]
     = REG_SAVED_VAL_OFFSET;
   fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].loc.offset
     = (_Unwind_Ptr) (sc->sc_pc) - new_cfa;
diff --git a/libgcc/config/m68k/linux-unwind.h b/libgcc/config/m68k/linux-unwind.h
index 1502ad1..ad0da69 100644
--- a/libgcc/config/m68k/linux-unwind.h
+++ b/libgcc/config/m68k/linux-unwind.h
@@ -68,21 +68,21 @@ m68k_fallback_frame_state (struct _Unwind_Context *context,
       fs->regs.cfa_reg = 15;
       fs->regs.cfa_offset = cfa - (long) context->cfa;
 
-      fs->regs.reg[0].how = REG_SAVED_OFFSET;
+      fs->regs.how[0] = REG_SAVED_OFFSET;
       fs->regs.reg[0].loc.offset = (long) &sc->sc_d0 - cfa;
-      fs->regs.reg[1].how = REG_SAVED_OFFSET;
+      fs->regs.how[1] = REG_SAVED_OFFSET;
       fs->regs.reg[1].loc.offset = (long) &sc->sc_d1 - cfa;
-      fs->regs.reg[8].how = REG_SAVED_OFFSET;
+      fs->regs.how[8] = REG_SAVED_OFFSET;
       fs->regs.reg[8].loc.offset = (long) &sc->sc_a0 - cfa;
-      fs->regs.reg[9].how = REG_SAVED_OFFSET;
+      fs->regs.how[9] = REG_SAVED_OFFSET;
       fs->regs.reg[9].loc.offset = (long) &sc->sc_a1 - cfa;
 
 #ifdef __uClinux__
-      fs->regs.reg[13].how = REG_SAVED_OFFSET;
+      fs->regs.how[13] = REG_SAVED_OFFSET;
       fs->regs.reg[13].loc.offset = (long) &sc->sc_a5 - cfa;
 #endif
 
-      fs->regs.reg[24].how = REG_SAVED_OFFSET;
+      fs->regs.how[24] = REG_SAVED_OFFSET;
       fs->regs.reg[24].loc.offset = (long) &sc->sc_pc - cfa;
 
 #ifndef __uClinux__
@@ -90,9 +90,9 @@ m68k_fallback_frame_state (struct _Unwind_Context *context,
 	{
 	  int *fpregs = (int *) sc->sc_fpregs;
 
-	  fs->regs.reg[16].how = REG_SAVED_OFFSET;
+	  fs->regs.how[16] = REG_SAVED_OFFSET;
 	  fs->regs.reg[16].loc.offset = (long) &fpregs[0] - cfa;
-	  fs->regs.reg[17].how = REG_SAVED_OFFSET;
+	  fs->regs.how[17] = REG_SAVED_OFFSET;
 	  fs->regs.reg[17].loc.offset = (long) &fpregs[M68K_FP_SIZE/4] - cfa;
 	}
 #elif defined __mcffpu__
@@ -124,12 +124,12 @@ m68k_fallback_frame_state (struct _Unwind_Context *context,
       /* register %d0-%d7/%a0-%a6  */
       for (i = 0; i <= 14; i++)
 	{
-	  fs->regs.reg[i].how = REG_SAVED_OFFSET;
+	  fs->regs.how[i] = REG_SAVED_OFFSET;
 	  fs->regs.reg[i].loc.offset = (long) &gregs[i] - cfa;
 	}
 
       /* return address  */
-      fs->regs.reg[24].how = REG_SAVED_OFFSET;
+      fs->regs.how[24] = REG_SAVED_OFFSET;
       fs->regs.reg[24].loc.offset = (long) &gregs[16] - cfa;
 
 #define uc_fpstate      uc_filler[0]
@@ -141,7 +141,7 @@ m68k_fallback_frame_state (struct _Unwind_Context *context,
 	  /* register %fp0-%fp7  */
 	  for (i = 16; i <= 23; i++)
 	    {
-	      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+	      fs->regs.how[i] = REG_SAVED_OFFSET;
 	      fs->regs.reg[i].loc.offset = fpregs - cfa;
 	      fpregs += M68K_FP_SIZE;
 	    }
diff --git a/libgcc/config/mips/linux-unwind.h b/libgcc/config/mips/linux-unwind.h
index e113f52..80e6e77 100644
--- a/libgcc/config/mips/linux-unwind.h
+++ b/libgcc/config/mips/linux-unwind.h
@@ -103,7 +103,7 @@ mips_fallback_frame_state (struct _Unwind_Context *context,
 #endif
 
   for (i = 0; i < 32; i++) {
-    fs->regs.reg[i].how = REG_SAVED_OFFSET;
+    fs->regs.how[i] = REG_SAVED_OFFSET;
     fs->regs.reg[i].loc.offset
       = (_Unwind_Ptr)&(sc->sc_regs[i]) + reg_offset - new_cfa;
   }
@@ -115,7 +115,7 @@ mips_fallback_frame_state (struct _Unwind_Context *context,
      Note that setting fs->signal_frame would not work.  As the comment
      above MASK_RETURN_ADDR explains, MIPS unwinders must earch for an
      odd-valued address.  */
-  fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].how
+  fs->regs.how[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__]
     = REG_SAVED_VAL_OFFSET;
   fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].loc.offset
     = (_Unwind_Ptr)(sc->sc_pc) + 2 - new_cfa;
diff --git a/libgcc/config/nds32/linux-unwind.h b/libgcc/config/nds32/linux-unwind.h
index 7a12d3a..cbb2620 100644
--- a/libgcc/config/nds32/linux-unwind.h
+++ b/libgcc/config/nds32/linux-unwind.h
@@ -92,7 +92,7 @@ nds32_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
 
 #define NDS32_PUT_FS_REG(NUM, NAME) \
-  (fs->regs.reg[NUM].how = REG_SAVED_OFFSET, \
+  (fs->regs.how[NUM] = REG_SAVED_OFFSET, \
    fs->regs.reg[NUM].loc.offset = (_Unwind_Ptr) &(sc_->NAME) - new_cfa)
 
   /* Restore all registers value.  */
diff --git a/libgcc/config/nios2/linux-unwind.h b/libgcc/config/nios2/linux-unwind.h
index 4a8fca4..aa27822 100644
--- a/libgcc/config/nios2/linux-unwind.h
+++ b/libgcc/config/nios2/linux-unwind.h
@@ -61,7 +61,7 @@ nios2_fallback_frame_state (struct _Unwind_Context *context,
     return _URC_END_OF_STACK;
 
 #define NIOS2_REG(NUM,NAME)						\
-  (fs->regs.reg[NUM].how = REG_SAVED_OFFSET,				\
+  (fs->regs.how[NUM] = REG_SAVED_OFFSET,				\
    fs->regs.reg[NUM].loc.offset = (_Unwind_Ptr)&(regs->NAME) - new_cfa)
 
   if (pc[0] == (0x00800004 | (__NR_rt_sigreturn << 6)))
diff --git a/libgcc/config/or1k/linux-unwind.h b/libgcc/config/or1k/linux-unwind.h
index 3cf9137..71171c5 100644
--- a/libgcc/config/or1k/linux-unwind.h
+++ b/libgcc/config/or1k/linux-unwind.h
@@ -59,10 +59,10 @@ or1k_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
   for (i = 2; i < 32; ++i)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset = (long) &sc->regs.gpr[i] - new_cfa;
     }
-  fs->regs.reg[32].how = REG_SAVED_OFFSET;
+  fs->regs.how[32] = REG_SAVED_OFFSET;
   fs->regs.reg[32].loc.offset = (long)&sc->regs.pc - new_cfa;
   fs->retaddr_column = 32;
   fs->signal_frame = 1;
diff --git a/libgcc/config/pa/hpux-unwind.h b/libgcc/config/pa/hpux-unwind.h
index f14812a..b30a67e 100644
--- a/libgcc/config/pa/hpux-unwind.h
+++ b/libgcc/config/pa/hpux-unwind.h
@@ -57,19 +57,19 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #endif
 
 #define UPDATE_FS_FOR_SAR(FS, N) \
-  (FS)->regs.reg[N].how = REG_SAVED_OFFSET;				\
+  (FS)->regs.how[N] = REG_SAVED_OFFSET;				\
   (FS)->regs.reg[N].loc.offset = GetSSRegAddr (mc, ss_cr11) - new_cfa
 
 #define UPDATE_FS_FOR_GR(FS, GRN, N) \
-  (FS)->regs.reg[N].how = REG_SAVED_OFFSET;				\
+  (FS)->regs.how[N] = REG_SAVED_OFFSET;				\
   (FS)->regs.reg[N].loc.offset = GetSSRegAddr (mc, ss_gr##GRN) - new_cfa
 
 #define UPDATE_FS_FOR_FR(FS, FRN, N) \
-  (FS)->regs.reg[N].how = REG_SAVED_OFFSET;				\
+  (FS)->regs.how[N] = REG_SAVED_OFFSET;				\
   (FS)->regs.reg[N].loc.offset = (long) &(mc->ss_fr##FRN) - new_cfa;
 
 #define UPDATE_FS_FOR_PC(FS, N) \
-  (FS)->regs.reg[N].how = REG_SAVED_OFFSET;				\
+  (FS)->regs.how[N] = REG_SAVED_OFFSET;				\
   (FS)->regs.reg[N].loc.offset = GetSSRegAddr (mc, ss_pcoq_head) - new_cfa
 
 /* Extract bit field from word using HP's numbering (MSB = 0).  */
@@ -151,7 +151,7 @@ pa_fallback_frame_state (struct _Unwind_Context *context,
       fs->regs.cfa_offset = 0;
 
       fs->retaddr_column = 0;
-      fs->regs.reg[0].how = REG_SAVED_OFFSET;
+      fs->regs.how[0] = REG_SAVED_OFFSET;
       fs->regs.reg[0].loc.offset = -24;
 
       /* Update context to describe the stub frame.  */
@@ -171,7 +171,7 @@ pa_fallback_frame_state (struct _Unwind_Context *context,
       fs->regs.cfa_offset = 0;
 
       fs->retaddr_column = 0;
-      fs->regs.reg[0].how = REG_SAVED_OFFSET;
+      fs->regs.how[0] = REG_SAVED_OFFSET;
       fs->regs.reg[0].loc.offset = -8;
 
       /* Update context to describe the stub frame.  */
diff --git a/libgcc/config/pa/linux-unwind.h b/libgcc/config/pa/linux-unwind.h
index 7e424c5..7efab00 100644
--- a/libgcc/config/pa/linux-unwind.h
+++ b/libgcc/config/pa/linux-unwind.h
@@ -138,22 +138,22 @@ pa32_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
   for (i = 1; i <= 31; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset = (long)&sc->sc_gr[i] - new_cfa;
     }
   for (i = 4; i <= 31; i++)
     {
       /* FP regs have left and right halves */
-      fs->regs.reg[2*i+24].how = REG_SAVED_OFFSET;
+      fs->regs.how[2*i+24] = REG_SAVED_OFFSET;
       fs->regs.reg[2*i+24].loc.offset
 	= (long)&sc->sc_fr[i] - new_cfa;
-      fs->regs.reg[2*i+24+1].how = REG_SAVED_OFFSET;
+      fs->regs.how[2*i+24+1] = REG_SAVED_OFFSET;
       fs->regs.reg[2*i+24+1].loc.offset
 	= (long)&sc->sc_fr[i] + 4 - new_cfa;
     }
-  fs->regs.reg[88].how = REG_SAVED_OFFSET;
+  fs->regs.how[88] = REG_SAVED_OFFSET;
   fs->regs.reg[88].loc.offset = (long) &sc->sc_sar - new_cfa;
-  fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].how
+  fs->regs.how[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__]
     = REG_SAVED_OFFSET;
   fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].loc.offset
     = (long) &sc->sc_iaoq[0] - new_cfa;
diff --git a/libgcc/config/riscv/linux-unwind.h b/libgcc/config/riscv/linux-unwind.h
index c86df2f..c44d1a8 100644
--- a/libgcc/config/riscv/linux-unwind.h
+++ b/libgcc/config/riscv/linux-unwind.h
@@ -73,13 +73,13 @@ riscv_fallback_frame_state (struct _Unwind_Context *context,
 
   for (i = 0; i < 32; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset = (_Unwind_Ptr) &sc->gregs[i] - new_cfa;
     }
 
   fs->signal_frame = 1;
   fs->retaddr_column = __LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__;
-  fs->regs.reg[fs->retaddr_column].how = REG_SAVED_VAL_OFFSET;
+  fs->regs.how[fs->retaddr_column] = REG_SAVED_VAL_OFFSET;
   fs->regs.reg[fs->retaddr_column].loc.offset =
     (_Unwind_Ptr) sc->gregs[0] - new_cfa;
 
diff --git a/libgcc/config/rs6000/aix-unwind.h b/libgcc/config/rs6000/aix-unwind.h
index d7e5f59..9a1efdc 100644
--- a/libgcc/config/rs6000/aix-unwind.h
+++ b/libgcc/config/rs6000/aix-unwind.h
@@ -40,7 +40,7 @@
 #ifdef __64BIT__
 #define MD_FROB_UPDATE_CONTEXT(CTX, FS)					\
   do {									\
-    if ((FS)->regs.reg[2].how == REG_UNSAVED)				\
+    if ((FS)->regs.how[2] == REG_UNSAVED)				\
       {									\
 	unsigned int *insn						\
 	  = (unsigned int *)						\
@@ -52,7 +52,7 @@
 #else
 #define MD_FROB_UPDATE_CONTEXT(CTX, FS)					\
   do {									\
-    if ((FS)->regs.reg[2].how == REG_UNSAVED)				\
+    if ((FS)->regs.how[2] == REG_UNSAVED)				\
       {									\
 	unsigned int *insn						\
 	  = (unsigned int *)						\
@@ -207,7 +207,7 @@ ucontext_for (struct _Unwind_Context *context)
 
 #define REGISTER_CFA_OFFSET_FOR(FS,REGNO,ADDR,CFA)\
 do { \
-(FS)->regs.reg[REGNO].how = REG_SAVED_OFFSET; \
+(FS)->regs.how[REGNO] = REG_SAVED_OFFSET; \
 (FS)->regs.reg[REGNO].loc.offset = (long) (ADDR) - (CFA); \
 } while (0)
 
diff --git a/libgcc/config/rs6000/darwin-fallback.c b/libgcc/config/rs6000/darwin-fallback.c
index c6bc69c..ad5c195 100644
--- a/libgcc/config/rs6000/darwin-fallback.c
+++ b/libgcc/config/rs6000/darwin-fallback.c
@@ -368,7 +368,7 @@ handle_syscall (_Unwind_FrameState *fs, const reg_unit gprs[32],
     return false;
 
 #define set_offset(r, addr)					\
-  (fs->regs.reg[r].how = REG_SAVED_OFFSET,			\
+  (fs->regs.how[r] = REG_SAVED_OFFSET,			\
    fs->regs.reg[r].loc.offset = (_Unwind_Ptr)(addr) - new_cfa)
 
   /* Restore even the registers that are not call-saved, since they
diff --git a/libgcc/config/rs6000/freebsd-unwind.h b/libgcc/config/rs6000/freebsd-unwind.h
index af96135..654e7f6 100644
--- a/libgcc/config/rs6000/freebsd-unwind.h
+++ b/libgcc/config/rs6000/freebsd-unwind.h
@@ -33,7 +33,7 @@ frob_update_context (struct _Unwind_Context *context,
   const unsigned int *pc = (const unsigned int *) context->ra;
 
 #ifdef __powerpc64__
-  if (fs->regs.reg[2].how == REG_UNSAVED)
+  if (fs->regs.how[2] == REG_UNSAVED)
     {
       /* If the current unwind info (FS) does not contain explicit info
 	 saving R2, then we have to do a minor amount of code reading to
diff --git a/libgcc/config/rs6000/linux-unwind.h b/libgcc/config/rs6000/linux-unwind.h
index 6a7c07f..f6ab939 100644
--- a/libgcc/config/rs6000/linux-unwind.h
+++ b/libgcc/config/rs6000/linux-unwind.h
@@ -215,12 +215,12 @@ ppc_fallback_frame_state (struct _Unwind_Context *context,
   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 
 #ifdef __powerpc64__
-  fs->regs.reg[2].how = REG_SAVED_OFFSET;
+  fs->regs.how[2] = REG_SAVED_OFFSET;
   fs->regs.reg[2].loc.offset = (long) &regs->gpr[2] - new_cfa;
 #endif
   for (i = 14; i < 32; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset = (long) &regs->gpr[i] - new_cfa;
     }
 
@@ -230,20 +230,20 @@ ppc_fallback_frame_state (struct _Unwind_Context *context,
   cr_offset += sizeof (long) - 4;
 #endif
   /* In the ELFv1 ABI, CR2 stands in for the whole CR.  */
-  fs->regs.reg[R_CR2].how = REG_SAVED_OFFSET;
+  fs->regs.how[R_CR2] = REG_SAVED_OFFSET;
   fs->regs.reg[R_CR2].loc.offset = cr_offset;
 #if _CALL_ELF == 2
   /* In the ELFv2 ABI, every CR field has a separate CFI entry.  */
-  fs->regs.reg[R_CR3].how = REG_SAVED_OFFSET;
+  fs->regs.how[R_CR3] = REG_SAVED_OFFSET;
   fs->regs.reg[R_CR3].loc.offset = cr_offset;
-  fs->regs.reg[R_CR4].how = REG_SAVED_OFFSET;
+  fs->regs.how[R_CR4] = REG_SAVED_OFFSET;
   fs->regs.reg[R_CR4].loc.offset = cr_offset;
 #endif
 
-  fs->regs.reg[R_LR].how = REG_SAVED_OFFSET;
+  fs->regs.how[R_LR] = REG_SAVED_OFFSET;
   fs->regs.reg[R_LR].loc.offset = (long) &regs->link - new_cfa;
 
-  fs->regs.reg[ARG_POINTER_REGNUM].how = REG_SAVED_OFFSET;
+  fs->regs.how[ARG_POINTER_REGNUM] = REG_SAVED_OFFSET;
   fs->regs.reg[ARG_POINTER_REGNUM].loc.offset = (long) &regs->nip - new_cfa;
   fs->retaddr_column = ARG_POINTER_REGNUM;
   fs->signal_frame = 1;
@@ -251,7 +251,7 @@ ppc_fallback_frame_state (struct _Unwind_Context *context,
   /* If we have a FPU...  */
   for (i = 14; i < 32; i++)
     {
-      fs->regs.reg[i + 32].how = REG_SAVED_OFFSET;
+      fs->regs.how[i + 32] = REG_SAVED_OFFSET;
       fs->regs.reg[i + 32].loc.offset = (long) &regs->fpr[i] - new_cfa;
     }
 
@@ -265,12 +265,12 @@ ppc_fallback_frame_state (struct _Unwind_Context *context,
     {
       for (i = 20; i < 32; i++)
 	{
-	  fs->regs.reg[i + R_VR0].how = REG_SAVED_OFFSET;
+	  fs->regs.how[i + R_VR0] = REG_SAVED_OFFSET;
 	  fs->regs.reg[i + R_VR0].loc.offset = (long) &vregs->vr[i] - new_cfa;
 	}
     }
 
-  fs->regs.reg[R_VRSAVE].how = REG_SAVED_OFFSET;
+  fs->regs.how[R_VRSAVE] = REG_SAVED_OFFSET;
   fs->regs.reg[R_VRSAVE].loc.offset = (long) &vregs->vsave - new_cfa;
 
   /* If we have SPE register high-parts... we check at compile-time to
@@ -278,7 +278,7 @@ ppc_fallback_frame_state (struct _Unwind_Context *context,
 #ifdef __SPE__
   for (i = 14; i < 32; i++)
     {
-      fs->regs.reg[i + FIRST_SPE_HIGH_REGNO - 4].how = REG_SAVED_OFFSET;
+      fs->regs.how[i + FIRST_SPE_HIGH_REGNO - 4] = REG_SAVED_OFFSET;
       fs->regs.reg[i + FIRST_SPE_HIGH_REGNO - 4].loc.offset
 	= (long) &regs->vregs - new_cfa + 4 * i;
     }
@@ -315,7 +315,7 @@ frob_update_context (struct _Unwind_Context *context, _Unwind_FrameState *fs ATT
 #endif
 
 #ifdef __powerpc64__
-  if (fs->regs.reg[2].how == REG_UNSAVED)
+  if (fs->regs.how[2] == REG_UNSAVED)
     {
       /* If the current unwind info (FS) does not contain explicit info
 	 saving R2, then we have to do a minor amount of code reading to
diff --git a/libgcc/config/s390/linux-unwind.h b/libgcc/config/s390/linux-unwind.h
index f3f1337..904bbaa 100644
--- a/libgcc/config/s390/linux-unwind.h
+++ b/libgcc/config/s390/linux-unwind.h
@@ -106,20 +106,20 @@ s390_fallback_frame_state (struct _Unwind_Context *context,
 
   for (i = 0; i < 16; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset =
 	(long)&regs->gprs[i] - new_cfa;
     }
   for (i = 0; i < 16; i++)
     {
-      fs->regs.reg[16+i].how = REG_SAVED_OFFSET;
+      fs->regs.how[16+i] = REG_SAVED_OFFSET;
       fs->regs.reg[16+i].loc.offset =
 	(long)&regs->fprs[dwarf_to_fpr_map[i]] - new_cfa;
     }
 
   /* Load return addr from PSW into dummy register 32.  */
 
-  fs->regs.reg[32].how = REG_SAVED_OFFSET;
+  fs->regs.how[32] = REG_SAVED_OFFSET;
   fs->regs.reg[32].loc.offset = (long)&regs->psw_addr - new_cfa;
   fs->retaddr_column = 32;
   /* SIGILL, SIGFPE and SIGTRAP are delivered with psw_addr
diff --git a/libgcc/config/s390/tpf-unwind.h b/libgcc/config/s390/tpf-unwind.h
index 526bdba..992cffc 100644
--- a/libgcc/config/s390/tpf-unwind.h
+++ b/libgcc/config/s390/tpf-unwind.h
@@ -88,18 +88,18 @@ s390_fallback_frame_state (struct _Unwind_Context *context,
       /* All registers remain unchanged ...  */
       for (i = 0; i < 32; i++)
 	{
-	  fs->regs.reg[i].how = REG_SAVED_REG;
+	  fs->regs.how[i] = REG_SAVED_REG;
 	  fs->regs.reg[i].loc.reg = i;
 	}
 
       /* ... except for %r14, which is stored at CFA+offset where offset
 	 is displacment of ICST_CRET or ICST_SRET from CFA */
       if ( __isPATrange(context->ra) )  {
-	   fs->regs.reg[14].how = REG_SAVED_OFFSET;
+	   fs->regs.how[14] = REG_SAVED_OFFSET;
 	   fs->regs.reg[14].loc.offset = ICST_CRET - STACK_POINTER_OFFSET;
 	   fs->retaddr_column = 14;
       }  else  {
-	   fs->regs.reg[14].how = REG_SAVED_OFFSET;
+	   fs->regs.how[14] = REG_SAVED_OFFSET;
 	   fs->regs.reg[14].loc.offset = ICST_SRET - STACK_POINTER_OFFSET;
 	   fs->retaddr_column = 14;
 
@@ -119,13 +119,13 @@ s390_fallback_frame_state (struct _Unwind_Context *context,
 
   for (i = 0; i < 16; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset = regs + i*8 - new_cfa;
     }
 
   for (i = 0; i < 4; i++)
     {
-      fs->regs.reg[16 + i].how = REG_SAVED_OFFSET;
+      fs->regs.how[16 + i] = REG_SAVED_OFFSET;
       fs->regs.reg[16 + i].loc.offset = regs + 16*8 + i*8 - new_cfa;
     }
 
diff --git a/libgcc/config/sh/linux-unwind.h b/libgcc/config/sh/linux-unwind.h
index 8cd30f4..8088e3c 100644
--- a/libgcc/config/sh/linux-unwind.h
+++ b/libgcc/config/sh/linux-unwind.h
@@ -99,24 +99,24 @@ sh_fallback_frame_state (struct _Unwind_Context *context,
 
   for (i = 0; i < 15; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset
 	= (long)&(sc->sc_regs[i]) - new_cfa;
     }
 
-  fs->regs.reg[SH_DWARF_FRAME_PR].how = REG_SAVED_OFFSET;
+  fs->regs.how[SH_DWARF_FRAME_PR] = REG_SAVED_OFFSET;
   fs->regs.reg[SH_DWARF_FRAME_PR].loc.offset
     = (long)&(sc->sc_pr) - new_cfa;
-  fs->regs.reg[SH_DWARF_FRAME_SR].how = REG_SAVED_OFFSET;
+  fs->regs.how[SH_DWARF_FRAME_SR] = REG_SAVED_OFFSET;
   fs->regs.reg[SH_DWARF_FRAME_SR].loc.offset
     = (long)&(sc->sc_sr) - new_cfa;
-  fs->regs.reg[SH_DWARF_FRAME_GBR].how = REG_SAVED_OFFSET;
+  fs->regs.how[SH_DWARF_FRAME_GBR] = REG_SAVED_OFFSET;
   fs->regs.reg[SH_DWARF_FRAME_GBR].loc.offset
     = (long)&(sc->sc_gbr) - new_cfa;
-  fs->regs.reg[SH_DWARF_FRAME_MACH].how = REG_SAVED_OFFSET;
+  fs->regs.how[SH_DWARF_FRAME_MACH] = REG_SAVED_OFFSET;
   fs->regs.reg[SH_DWARF_FRAME_MACH].loc.offset
     = (long)&(sc->sc_mach) - new_cfa;
-  fs->regs.reg[SH_DWARF_FRAME_MACL].how = REG_SAVED_OFFSET;
+  fs->regs.how[SH_DWARF_FRAME_MACL] = REG_SAVED_OFFSET;
   fs->regs.reg[SH_DWARF_FRAME_MACL].loc.offset
     = (long)&(sc->sc_macl) - new_cfa;
 
@@ -124,7 +124,7 @@ sh_fallback_frame_state (struct _Unwind_Context *context,
   r = SH_DWARF_FRAME_FP0;
   for (i = 0; i < 16; i++)
     {
-      fs->regs.reg[r+i].how = REG_SAVED_OFFSET;
+      fs->regs.how[r+i] = REG_SAVED_OFFSET;
       fs->regs.reg[r+i].loc.offset
 	= (long)&(sc->sc_fpregs[i]) - new_cfa;
     }
@@ -132,20 +132,20 @@ sh_fallback_frame_state (struct _Unwind_Context *context,
   r = SH_DWARF_FRAME_XD0;
   for (i = 0; i < 8; i++)
     {
-      fs->regs.reg[r+i].how = REG_SAVED_OFFSET;
+      fs->regs.how[r+i] = REG_SAVED_OFFSET;
       fs->regs.reg[r+i].loc.offset
 	= (long)&(sc->sc_xfpregs[2*i]) - new_cfa;
     }
 
-  fs->regs.reg[SH_DWARF_FRAME_FPUL].how = REG_SAVED_OFFSET;
+  fs->regs.how[SH_DWARF_FRAME_FPUL] = REG_SAVED_OFFSET;
   fs->regs.reg[SH_DWARF_FRAME_FPUL].loc.offset
     = (long)&(sc->sc_fpul) - new_cfa;
-  fs->regs.reg[SH_DWARF_FRAME_FPSCR].how = REG_SAVED_OFFSET;
+  fs->regs.how[SH_DWARF_FRAME_FPSCR] = REG_SAVED_OFFSET;
   fs->regs.reg[SH_DWARF_FRAME_FPSCR].loc.offset
     = (long)&(sc->sc_fpscr) - new_cfa;
 #endif
 
-  fs->regs.reg[SH_DWARF_FRAME_PC].how = REG_SAVED_OFFSET;
+  fs->regs.how[SH_DWARF_FRAME_PC] = REG_SAVED_OFFSET;
   fs->regs.reg[SH_DWARF_FRAME_PC].loc.offset
     = (long)&(sc->sc_pc) - new_cfa;
   fs->retaddr_column = SH_DWARF_FRAME_PC;
diff --git a/libgcc/config/sparc/linux-unwind.h b/libgcc/config/sparc/linux-unwind.h
index 001429e..0095b43 100644
--- a/libgcc/config/sparc/linux-unwind.h
+++ b/libgcc/config/sparc/linux-unwind.h
@@ -65,13 +65,13 @@ sparc64_fallback_frame_state (struct _Unwind_Context *context,
       if ((unsigned int) i == __builtin_dwarf_sp_column ())
 	continue;
 
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset
 	= this_cfa + regs_off + (i * 8) - new_cfa;
     }
   for (i = 0; i < 16; i++)
     {
-      fs->regs.reg[i + 16].how = REG_SAVED_OFFSET;
+      fs->regs.how[i + 16] = REG_SAVED_OFFSET;
       fs->regs.reg[i + 16].loc.offset
 	= this_cfa + (i * 8) - new_cfa;
     }
@@ -81,7 +81,7 @@ sparc64_fallback_frame_state (struct _Unwind_Context *context,
 	{
 	  if (i > 32 && (i & 0x1))
 	    continue;
-	  fs->regs.reg[i + 32].how = REG_SAVED_OFFSET;
+	  fs->regs.how[i + 32] = REG_SAVED_OFFSET;
 	  fs->regs.reg[i + 32].loc.offset
 	    = fpu_save + (i * 4) - new_cfa;
 	}
@@ -95,7 +95,7 @@ sparc64_fallback_frame_state (struct _Unwind_Context *context,
   shifted_ra_location = this_cfa + regs_off + 19 * 8; /* Y register */
   *(long *)shifted_ra_location = *(long *)ra_location - 8;
   fs->retaddr_column = 0;
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = shifted_ra_location - new_cfa;
   fs->signal_frame = 1;
 
@@ -122,7 +122,7 @@ sparc64_frob_update_context (struct _Unwind_Context *context,
       context->cfa -= STACK_BIAS;
 
       for (i = 0; i < __LIBGCC_DWARF_FRAME_REGISTERS__ + 1; ++i)
-	if (fs->regs.reg[i].how == REG_SAVED_OFFSET)
+	if (fs->regs.how[i] == REG_SAVED_OFFSET)
 	  _Unwind_SetGRPtr (context, i,
 			    _Unwind_GetGRPtr (context, i) - STACK_BIAS);
     }
@@ -177,13 +177,13 @@ sparc_fallback_frame_state (struct _Unwind_Context *context,
       if ((unsigned int) i == __builtin_dwarf_sp_column ())
 	continue;
 
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset
 	= this_cfa + regs_off + (4 * 4) + (i * 4) - new_cfa;
     }
   for (i = 0; i < 16; i++)
     {
-      fs->regs.reg[i + 16].how = REG_SAVED_OFFSET;
+      fs->regs.how[i + 16] = REG_SAVED_OFFSET;
       fs->regs.reg[i + 16].loc.offset
 	= this_cfa + (i * 4) - new_cfa;
     }
@@ -191,7 +191,7 @@ sparc_fallback_frame_state (struct _Unwind_Context *context,
     {
       for (i = 0; i < 32; i++)
 	{
-	  fs->regs.reg[i + 32].how = REG_SAVED_OFFSET;
+	  fs->regs.how[i + 32] = REG_SAVED_OFFSET;
 	  fs->regs.reg[i + 32].loc.offset
 	    = fpu_save + (i * 4) - new_cfa;
 	}
@@ -205,7 +205,7 @@ sparc_fallback_frame_state (struct _Unwind_Context *context,
   shifted_ra_location = this_cfa + regs_off + 3 * 4; /* Y register */
   *(int *)shifted_ra_location = *(int *)ra_location - 8;
   fs->retaddr_column = 0;
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = shifted_ra_location - new_cfa;
   fs->signal_frame = 1;
 
diff --git a/libgcc/config/sparc/sol2-unwind.h b/libgcc/config/sparc/sol2-unwind.h
index 06cc538..4da5a7c 100644
--- a/libgcc/config/sparc/sol2-unwind.h
+++ b/libgcc/config/sparc/sol2-unwind.h
@@ -96,7 +96,7 @@ sparc64_frob_update_context (struct _Unwind_Context *context,
       context->cfa -= STACK_BIAS;
 
       for (i = 0; i < __LIBGCC_DWARF_FRAME_REGISTERS__ + 1; ++i)
-	if (fs->regs.reg[i].how == REG_SAVED_OFFSET)
+	if (fs->regs.how[i] == REG_SAVED_OFFSET)
 	  _Unwind_SetGRPtr (context, i,
 			    _Unwind_GetGRPtr (context, i) - STACK_BIAS);
     }
@@ -221,7 +221,7 @@ MD_FALLBACK_FRAME_STATE_FOR (struct _Unwind_Context *context,
 	continue;
 
       /* First the global registers and then the out registers.  */
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset = (long)&mctx->gregs[REG_Y + i] - new_cfa;
     }
 
@@ -229,7 +229,7 @@ MD_FALLBACK_FRAME_STATE_FOR (struct _Unwind_Context *context,
      the register window (in and local registers) was saved.  */
   for (i = 0; i < 16; i++)
     {
-      fs->regs.reg[i + 16].how = REG_SAVED_OFFSET;
+      fs->regs.how[i + 16] = REG_SAVED_OFFSET;
       fs->regs.reg[i + 16].loc.offset = i * sizeof(long);
     }
 
@@ -238,7 +238,7 @@ MD_FALLBACK_FRAME_STATE_FOR (struct _Unwind_Context *context,
     {
       for (i = 0; i < 32; i++)
 	{
-	  fs->regs.reg[i + 32].how = REG_SAVED_OFFSET;
+	  fs->regs.how[i + 32] = REG_SAVED_OFFSET;
 	  fs->regs.reg[i + 32].loc.offset
 	    = (long)&mctx->fpregs.fpu_fr.fpu_regs[i] - new_cfa;
 	}
@@ -250,7 +250,7 @@ MD_FALLBACK_FRAME_STATE_FOR (struct _Unwind_Context *context,
 	  if (i > 32 && (i & 1))
 	    continue;
 
-	  fs->regs.reg[i + 32].how = REG_SAVED_OFFSET;
+	  fs->regs.how[i + 32] = REG_SAVED_OFFSET;
 	  fs->regs.reg[i + 32].loc.offset
 	    = (long)&mctx->fpregs.fpu_fr.fpu_dregs[i/2] - new_cfa;
 	}
@@ -265,7 +265,7 @@ MD_FALLBACK_FRAME_STATE_FOR (struct _Unwind_Context *context,
   shifted_ra_location = &mctx->gregs[REG_Y];
   *(void **)shifted_ra_location = *(void **)ra_location - 8;
   fs->retaddr_column = 0;
-  fs->regs.reg[0].how = REG_SAVED_OFFSET;
+  fs->regs.how[0] = REG_SAVED_OFFSET;
   fs->regs.reg[0].loc.offset = (long)shifted_ra_location - new_cfa;
 
   /* SIGFPE for IEEE-754 exceptions is delivered after the faulting insn
diff --git a/libgcc/config/xtensa/linux-unwind.h b/libgcc/config/xtensa/linux-unwind.h
index fed118e..868624e 100644
--- a/libgcc/config/xtensa/linux-unwind.h
+++ b/libgcc/config/xtensa/linux-unwind.h
@@ -105,11 +105,11 @@ xtensa_fallback_frame_state (struct _Unwind_Context *context,
 
   for (i = 0; i < 16; i++)
     {
-      fs->regs.reg[i].how = REG_SAVED_OFFSET;
+      fs->regs.how[i] = REG_SAVED_OFFSET;
       fs->regs.reg[i].loc.offset = (_Unwind_Ptr) &(sc->sc_a[i]) - new_cfa;
     }
 
-  fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].how =
+  fs->regs.how[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__] =
     REG_SAVED_VAL_OFFSET;
   fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].loc.offset =
     (_Unwind_Ptr) (sc->sc_pc) - new_cfa;
diff --git a/libgcc/unwind-dw2.c b/libgcc/unwind-dw2.c
index a2eb66d..eaceace 100644
--- a/libgcc/unwind-dw2.c
+++ b/libgcc/unwind-dw2.c
@@ -36,6 +36,7 @@
 #include "unwind-dw2-fde.h"
 #include "gthr.h"
 #include "unwind-dw2.h"
+#include <stddef.h>
 
 #ifdef HAVE_SYS_SDT_H
 #include <sys/sdt.h>
@@ -983,7 +984,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
 	    {
-	      fs->regs.reg[reg].how = REG_SAVED_OFFSET;
+	      fs->regs.how[reg] = REG_SAVED_OFFSET;
 	      fs->regs.reg[reg].loc.offset = offset;
 	    }
 	}
@@ -992,7 +993,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  reg = insn & 0x3f;
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
-	    fs->regs.reg[reg].how = REG_UNSAVED;
+	    fs->regs.how[reg] = REG_UNSAVED;
 	}
       else switch (insn)
 	{
@@ -1026,7 +1027,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
 	    {
-	      fs->regs.reg[reg].how = REG_SAVED_OFFSET;
+	      fs->regs.how[reg] = REG_SAVED_OFFSET;
 	      fs->regs.reg[reg].loc.offset = offset;
 	    }
 	  break;
@@ -1037,21 +1038,21 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	     register was saved somewhere.  */
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
-	    fs->regs.reg[reg].how = REG_UNSAVED;
+	    fs->regs.how[reg] = REG_UNSAVED;
 	  break;
 
 	case DW_CFA_same_value:
 	  insn_ptr = read_uleb128 (insn_ptr, &reg);
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
-	    fs->regs.reg[reg].how = REG_UNSAVED;
+	    fs->regs.how[reg] = REG_UNSAVED;
 	  break;
 
 	case DW_CFA_undefined:
 	  insn_ptr = read_uleb128 (insn_ptr, &reg);
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
-	    fs->regs.reg[reg].how = REG_UNDEFINED;
+	    fs->regs.how[reg] = REG_UNDEFINED;
 	  break;
 
 	case DW_CFA_nop:
@@ -1065,7 +1066,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	    reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	    if (UNWIND_COLUMN_IN_RANGE (reg))
 	      {
-	        fs->regs.reg[reg].how = REG_SAVED_REG;
+		fs->regs.how[reg] = REG_SAVED_REG;
 	        fs->regs.reg[reg].loc.reg = (_Unwind_Word)reg2;
 	      }
 	  }
@@ -1128,7 +1129,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
 	    {
-	      fs->regs.reg[reg].how = REG_SAVED_EXP;
+	      fs->regs.how[reg] = REG_SAVED_EXP;
 	      fs->regs.reg[reg].loc.exp = insn_ptr;
 	    }
 	  insn_ptr = read_uleb128 (insn_ptr, &utmp);
@@ -1143,7 +1144,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
 	    {
-	      fs->regs.reg[reg].how = REG_SAVED_OFFSET;
+	      fs->regs.how[reg] = REG_SAVED_OFFSET;
 	      fs->regs.reg[reg].loc.offset = offset;
 	    }
 	  break;
@@ -1171,7 +1172,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
 	    {
-	      fs->regs.reg[reg].how = REG_SAVED_VAL_OFFSET;
+	      fs->regs.how[reg] = REG_SAVED_VAL_OFFSET;
 	      fs->regs.reg[reg].loc.offset = offset;
 	    }
 	  break;
@@ -1183,7 +1184,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
 	    {
-	      fs->regs.reg[reg].how = REG_SAVED_VAL_OFFSET;
+	      fs->regs.how[reg] = REG_SAVED_VAL_OFFSET;
 	      fs->regs.reg[reg].loc.offset = offset;
 	    }
 	  break;
@@ -1193,7 +1194,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
 	    {
-	      fs->regs.reg[reg].how = REG_SAVED_VAL_EXP;
+	      fs->regs.how[reg] = REG_SAVED_VAL_EXP;
 	      fs->regs.reg[reg].loc.exp = insn_ptr;
 	    }
 	  insn_ptr = read_uleb128 (insn_ptr, &utmp);
@@ -1205,14 +1206,14 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  /* This CFA is multiplexed with Sparc.  On AArch64 it's used to toggle
 	     return address signing status.  */
 	  reg = DWARF_REGNUM_AARCH64_RA_STATE;
-	  gcc_assert (fs->regs.reg[reg].how == REG_UNSAVED);
+	  gcc_assert (fs->regs.how[reg] == REG_UNSAVED);
 	  fs->regs.reg[reg].loc.offset ^= 1;
 #else
 	  /* ??? Hardcoded for SPARC register window configuration.  */
 	  if (__LIBGCC_DWARF_FRAME_REGISTERS__ >= 32)
 	    for (reg = 16; reg < 32; ++reg)
 	      {
-		fs->regs.reg[reg].how = REG_SAVED_OFFSET;
+		fs->regs.how[reg] = REG_SAVED_OFFSET;
 		fs->regs.reg[reg].loc.offset = (reg - 16) * sizeof (void *);
 	      }
 #endif
@@ -1232,7 +1233,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  reg = DWARF_REG_TO_UNWIND_COLUMN (reg);
 	  if (UNWIND_COLUMN_IN_RANGE (reg))
 	    {
-	      fs->regs.reg[reg].how = REG_SAVED_OFFSET;
+	      fs->regs.how[reg] = REG_SAVED_OFFSET;
 	      fs->regs.reg[reg].loc.offset = -offset;
 	    }
 	  break;
@@ -1255,7 +1256,8 @@ uw_frame_state_for (struct _Unwind_Context *context, _Unwind_FrameState *fs)
   const struct dwarf_cie *cie;
   const unsigned char *aug, *insn, *end;
 
-  memset (fs, 0, sizeof (*fs));
+  memset (&fs->regs.how[0], 0,
+	  sizeof (*fs) - offsetof (_Unwind_FrameState, regs.how[0]));
   context->args_size = 0;
   context->lsda = 0;
 
@@ -1355,7 +1357,7 @@ __frame_state_for (void *pc_target, struct frame_state *state_in)
 
   for (reg = 0; reg < PRE_GCC3_DWARF_FRAME_REGISTERS + 1; reg++)
     {
-      state_in->saved[reg] = fs.regs.reg[reg].how;
+      state_in->saved[reg] = fs.regs.how[reg];
       switch (state_in->saved[reg])
 	{
 	case REG_SAVED_REG:
@@ -1453,7 +1455,7 @@ uw_update_context_1 (struct _Unwind_Context *context, _Unwind_FrameState *fs)
 
   /* Compute the addresses of all registers saved in this frame.  */
   for (i = 0; i < __LIBGCC_DWARF_FRAME_REGISTERS__ + 1; ++i)
-    switch (fs->regs.reg[i].how)
+    switch (fs->regs.how[i])
       {
       case REG_UNSAVED:
       case REG_UNDEFINED:
@@ -1531,7 +1533,7 @@ uw_update_context (struct _Unwind_Context *context, _Unwind_FrameState *fs)
      rule is handled like same_value.  The only exception is
      DW_CFA_undefined on retaddr_column which is supposed to
      mark outermost frame in DWARF 3.  */
-  if (fs->regs.reg[DWARF_REG_TO_UNWIND_COLUMN (fs->retaddr_column)].how
+  if (fs->regs.how[DWARF_REG_TO_UNWIND_COLUMN (fs->retaddr_column)]
       == REG_UNDEFINED)
     /* uw_frame_state_for uses context->ra == 0 check to find outermost
        stack frame.  */
diff --git a/libgcc/unwind-dw2.h b/libgcc/unwind-dw2.h
index 0c478e5..af34e00 100644
--- a/libgcc/unwind-dw2.h
+++ b/libgcc/unwind-dw2.h
@@ -22,6 +22,16 @@
    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
    <http://www.gnu.org/licenses/>.  */
 
+enum {
+  REG_UNSAVED,
+  REG_SAVED_OFFSET,
+  REG_SAVED_REG,
+  REG_SAVED_EXP,
+  REG_SAVED_VAL_OFFSET,
+  REG_SAVED_VAL_EXP,
+  REG_UNDEFINED
+};
+
 /* The result of interpreting the frame unwind info for a frame.
    This is all symbolic at this point, as none of the values can
    be resolved until the target pc is located.  */
@@ -37,16 +47,8 @@ typedef struct
 	_Unwind_Sword offset;
 	const unsigned char *exp;
       } loc;
-      enum {
-	REG_UNSAVED,
-	REG_SAVED_OFFSET,
-	REG_SAVED_REG,
-	REG_SAVED_EXP,
-	REG_SAVED_VAL_OFFSET,
-	REG_SAVED_VAL_EXP,
-	REG_UNDEFINED
-      } how;
     } reg[__LIBGCC_DWARF_FRAME_REGISTERS__+1];
+    unsigned char how[__LIBGCC_DWARF_FRAME_REGISTERS__+1];
 
     /* Used to implement DW_CFA_remember_state.  */
     struct frame_state_reg_info *prev;