aix: Permit use of AIX Vector extended ABI mode

AIX only permits use of Altivec VSRs 20-31 in a Vector Extended ABI mode.
This patch explicitly enables use of the VSRs using the new -mabi=vec-extabi
command line option also implemented in LLVM for AIX.

Bootstrapped on powerpc-ibm-aix7.2.3.0 and powerpc64le-linux-gnu.

gcc/ChangeLog:

	* config/rs6000/rs6000.opt (mabi=vec-extabi): New.
	(mabi=vec-default): New.
	* config/rs6000/rs6000-c.c (rs6000_target_modify_macros): Define
	__EXTABI__ for AIX Vector extended ABI.
	* config/rs6000/rs6000.c (rs6000_debug_reg_global): Print AIX Vector
	extabi info.
	(conditional_register_usage): If AIX vec_extabi enabled, vs20-vs31
	are non-volatile.
	* doc/invoke.texi (PowerPC mabi): Add AIX vec-extabi and vec-default.

4 files changed, 20 insertions, 3 deletions

diff --git a/gcc/config/rs6000/rs6000-c.c b/gcc/config/rs6000/rs6000-c.c
index 656cdb3..06b3bc0 100644
--- a/gcc/config/rs6000/rs6000-c.c
+++ b/gcc/config/rs6000/rs6000-c.c
@@ -483,6 +483,8 @@ rs6000_target_modify_macros (bool define_p, HOST_WIDE_INT flags,
 	  /* Define this when supporting context-sensitive keywords.  */
       if (!flag_iso)
 	rs6000_define_or_undefine_macro (define_p, "__APPLE_ALTIVEC__");
+      if (rs6000_aix_extabi)
+	rs6000_define_or_undefine_macro (define_p, "__EXTABI__");
     }
   /* Note that the OPTION_MASK_VSX flag is automatically turned on in
      the following conditions:
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index fbaff28..0d5ef38 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -2512,6 +2512,9 @@ rs6000_debug_reg_global (void)
   if (rs6000_altivec_abi)
     fprintf (stderr, DEBUG_FMT_S, "altivec_abi", "true");
 
+  if (rs6000_aix_extabi)
+    fprintf (stderr, DEBUG_FMT_S, "AIX vec-extabi", "true");
+
   if (rs6000_darwin64_abi)
     fprintf (stderr, DEBUG_FMT_S, "darwin64_abi", "true");
 
@@ -9815,7 +9818,7 @@ rs6000_conditional_register_usage (void)
 	call_used_regs[i] = 1;
 
       /* AIX reserves VR20:31 in non-extended ABI mode.  */
-      if (TARGET_XCOFF)
+      if (TARGET_XCOFF && !rs6000_aix_extabi)
 	for (i = FIRST_ALTIVEC_REGNO + 20; i < FIRST_ALTIVEC_REGNO + 32; ++i)
 	  fixed_regs[i] = call_used_regs[i] = 1;
     }
diff --git a/gcc/config/rs6000/rs6000.opt b/gcc/config/rs6000/rs6000.opt
index 6240f77..7aaabf3 100644
--- a/gcc/config/rs6000/rs6000.opt
+++ b/gcc/config/rs6000/rs6000.opt
@@ -352,6 +352,7 @@ mdebug=
 Target RejectNegative Joined
 -mdebug=	Enable debug output.
 
+; Altivec ABI
 mabi=altivec
 Target RejectNegative Var(rs6000_altivec_abi) Save
 Use the AltiVec ABI extensions.
@@ -360,6 +361,16 @@ mabi=no-altivec
 Target RejectNegative Var(rs6000_altivec_abi, 0)
 Do not use the AltiVec ABI extensions.
 
+; AIX Extended vector ABI
+mabi=vec-extabi
+Target RejectNegative Var(rs6000_aix_extabi, 1) Save
+Use the AIX Vector Extended ABI
+
+mabi=vec-default
+Target RejectNegative Var(rs6000_aix_extabi, 0)
+Do not use the AIX Vector Extended ABI
+
+; PPC64 Linux ELF ABI
 mabi=elfv1
 Target RejectNegative Var(rs6000_elf_abi, 1) Save
 Use the ELFv1 ABI.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index a89d385..3751bc3 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -27509,9 +27509,10 @@ SVR4 ABI)@.
 @item -mabi=@var{abi-type}
 @opindex mabi
 Extend the current ABI with a particular extension, or remove such extension.
-Valid values are @samp{altivec}, @samp{no-altivec},
+Valid values are: @samp{altivec}, @samp{no-altivec},
 @samp{ibmlongdouble}, @samp{ieeelongdouble},
-@samp{elfv1}, @samp{elfv2}@.
+@samp{elfv1}, @samp{elfv2},
+and for AIX: @samp{vec-extabi}, @samp{vec-default}@.
 
 @item -mabi=ibmlongdouble
 @opindex mabi=ibmlongdouble