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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.
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PowerPC Darwin8 is the last version to use an unwind frame fallback routine.
This had been omitted from the new shared EH library, along with one more
header dependency that only fires there.
Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
libgcc/ChangeLog:
* config/rs6000/t-darwin-ehs: Add darwin-fallback.o.
* config/t-darwin-ehs: Add dependency on unwind.h.
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There was a race condition where the link for the new shared EH library
(only used on earlier Darwin) could fail because the new crts had not been
copied to the gcc directory. This can cause a build failure (although
currently only seen on powerpc-darwin).
Fixed by adding specific dependency on the crts and on the multi target.
We also add the declaration header for the Darwin10 unwinder shim to the
powerpc cases, since we build that there for Rosetta use.
Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
libgcc/ChangeLog:
* config.host: Add shim declaration header to powerpc*-darwin builds.
* config/rs6000/t-darwin-ehs: Remove dependency on the powerpc end
file.
* config/t-darwin-ehs: Add dependencies to the shared unwinder
objects.
* config/t-slibgcc-darwin: Add extra_parts to the dependencies for
the shared EH lib. Add all-multi to the dependencies for the
libgcc_s.1.dylib redirections.
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This removes ibm-ldouble.c and a few eabi crt files from the build
closure, which were producing objects we don't use anyway.
2021-12-07 Rasmus Villemoes <rv@rasmusvillemoes.dk>
libgcc/
* config/rs6000/t-vxworks: New file.
* config.host (powerpc*-*-vxworks*): Use it instead of
t-ppccomm.
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In order to reslve a long-standing issue with inter-operation
with libSystem, we have bumped the SO name for libgcc_s.
Distributions might wish to install this new version into a
structure where exisiting code is already linked with the
compiler-local libgcc_s.1 (providing symbols exported by the
now-retired libgcc_ext.10.x shims).
The replacement libgcc_s.1 forwards the symbols from the new SO.
In order to support DYLD_LIBRARY_PATH on systems (where it works)
we forward the libSystem unwinder symbols from 10.7+ and a
compiler-local version of the libgcc unwinder on earlier.
For macOS 10.4 to 10.6 this is 'bug-compatible' with existing uses.
For 10.7+ the behaviour will now actually be correct.
This should be squashed with the initial libgcc changes for PR80556
in any backport (r12-5418-gd4943ce939d)
libgcc/ChangeLog:
* config.host (*-*-darwin*): Add logic to build a shared
unwinder library for Darwin8-10.
* config/i386/t-darwin: Build legacy libgcc_s.1.
* config/rs6000/t-darwin: Likewise.
* config/t-darwin: Reorganise the EH fragments to place
them for inclusion in a shared EH lib.
* config/t-slibgcc-darwin: Build a legacy libgcc_s.1 and
the supporting pieces (all FAT libs).
* config/t-darwin-noeh: Removed.
* config/darwin-unwind.ver: New file.
* config/rs6000/t-darwin-ehs: New file.
* config/t-darwin-ehs: New file.
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This addresses a long-standing problem where a work-around for an unwinder
issue (also a regression) regresses other functionality. The patch replaces
several work-arounds with a fix for PR80556 and a work-around for PR88590.
* The fix for PR80556 requires a bump to the SO name for libgcc_s, since we
need to remove the unwinder symbols from it. This would trigger PR88590
hence the work-around for that.
* We weaken the symbols for emulated TLS support so that it is possible
for a DSO linked with static-libgcc to interoperate with a DSO linked with
libgcc_s. Likewise main exes.
* We remove all the gcc-4.2.1 era stubs machinery and workarounds.
* libgcc is always now linked ahead of libc, which avoids fails where the
libc (libSystem) builtins implementations are not up to date.
* The unwinder now always comes from the system
- for Darwin9 from /usr/lib/libgcc_s.1.dylib
- for Darwin10 from /usr/lib/libSystem.dylib
- for Darwin11+ from /usr/lib/system/libunwind.dylib.
We still insert a shim on Darwin10 to fix an omitted unwind function, but
the underlying unwinder remains the system one.
* The work-around for PR88590 has two parts (1) we always link libgcc from
its convenience lib on affected system versions (avoiding the need to find
the DSO path); (2) we add and export the emutls functions from DSOs - this
makes a relatively small (20k) addition to a DSO. These can be backed out
when a proper fix for PR88590 is committed.
For distributions that wish to install a libgcc_s.1.dylib to satisfy linkage
from exes that linked against the stubs can use a reexported libgcc_s.1.1
(since that contains all the symbols that were previously exported via the
stubs).
Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
gcc/ChangeLog:
PR target/80556
* config/darwin-driver.c (darwin_driver_init): Handle exported
symbols and symbol lists (suppress automatic export of the TLS
symbols).
* config/darwin.c (darwin_rename_builtins): Remove workaround.
* config/darwin.h (LINK_GCC_C_SEQUENCE_SPEC): Likewise.
(REAL_LIBGCC_SPEC): Handle revised library uses.
* config/darwin.opt (nodefaultexport): New.
* config/i386/darwin.h (PR80556_WORKAROUND): Remove.
* config/i386/darwin32-biarch.h (PR80556_WORKAROUND): Likewise.
* config/i386/darwin64-biarch.h (PR80556_WORKAROUND): Likewise.
libgcc/ChangeLog:
* config.host: Add weak emutls crt to the extra_parts.
* config/i386/darwin-lib.h (DECLARE_LIBRARY_RENAMES): Remove
workaround.
* config/libgcc-libsystem.ver: Add exclude list for the system-
provided unwinder.
* config/t-slibgcc-darwin: Bump SO version, remove stubs code.
* config/i386/libgcc-darwin.10.4.ver: Removed.
* config/i386/libgcc-darwin.10.5.ver: Removed.
* config/rs6000/libgcc-darwin.10.4.ver: Removed.
* config/rs6000/libgcc-darwin.10.5.ver: Removed.
* config/t-darwin-noeh: New file.
gcc/testsuite/ChangeLog:
* gcc.dg/torture/fp-int-convert-timode-3.c: Remove XFAIL.
* gcc.dg/torture/fp-int-convert-timode-4.c: Likewise.
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At the end of the backtrace stream _Unwind_Find_FDE() may not be able
to find the frame unwind info and will later call the backtrace fallback
instead of finishing. This occurs when using an old libc on ppc64 due to
dl_iterate_phdr() not being able to set the fde in the last trace.
When this occurs the cfa of the trace will be behind of context's cfa.
Also, libgo’s probestackmaps() calls the backtrace with a null pointer
and can get to the backchain fallback with the same problem, in this case
we are only interested in find a stack map, we don't need nor can do a
backchain.
_Unwind_ForcedUnwind_Phase2() can hit the same issue as it uses
uw_frame_state_for(), so we need to treat _URC_NORMAL_STOP.
libgcc/ChangeLog:
PR libgcc/103044
* config/rs6000/linux-unwind.h (ppc_backchain_fallback): Check if it's
called with a null argument or at the end of the backtrace and return.
* unwind.inc (_Unwind_ForcedUnwind_Phase2): Treat _URC_NORMAL_STOP.
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Jonathan reported and I've verified a
In file included from ../../../libgcc/unwind-dw2.c:412:
./md-unwind-support.h:398:6: warning: no previous prototype for ‘ppc_backchain_fallback’ [-Wmissing-prototypes]
398 | void ppc_backchain_fallback (struct _Unwind_Context *context, void *a)
| ^~~~~~~~~~~~~~~~~~~~~~
warning on powerpc*-linux* libgcc build.
All the other MD_* macro functions are static, so I think the following
is the right thing rather than adding a previous prototype for
ppc_backchain_fallback.
2021-11-10 Jakub Jelinek <jakub@redhat.com>
* config/rs6000/linux-unwind.h (ppc_back_fallback): Make it static,
formatting fix.
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Without dwarf2 unwind tables available _Unwind_Backtrace() is not
able to return the full backtrace.
This patch adds a fallback function on powerpc to get the backtrace
by doing a backchain, this code was originally at glibc.
libgcc/ChangeLog:
* config/rs6000/linux-unwind.h (struct rt_sigframe): Move it to
outside of get_regs() in order to use it in another function, this
is done twice: for __powerpc64__ and for !__powerpc64__.
(struct trace_arg): New struct.
(struct layout): New struct.
(ppc_backchain_fallback): New function.
* unwind.inc (_Unwind_Backtrace): Look for _URC_NORMAL_STOP code
state and call MD_BACKCHAIN_FALLBACK.
gcc/testsuite/ChangeLog:
* gcc.target/powerpc/unwind-backchain.c: New test.
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* config/i386/morestack.S: Use .init_array for constructor if
available.
* config/rs6000/morestack.S: Likewise.
* config/s390/morestack.S: Likewise.
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While performing some tests of IEEE 128 float for PPC64LE, Michael
Meissner noticed that __gcc_qsub is substantially slower than
__gcc_qadd. __gcc_qsub calls __gcc_add with the second operand
negated. Because the functions normally are invoked through
libgcc shared object, the extra PLT overhead has a large impact
on the overall time of the function. This patch converts
__gcc_qadd to a static inline function invoked by __gcc_qadd
and __gcc_qsub.
libgcc/ChangeLog:
* config/rs6000/ibm-ldouble.c (ldouble_qadd_internal): Rename from
__gcc_qadd.
(__gcc_qadd): Call ldouble_qadd_internal.
(__gcc_qsub): Call ldouble_qadd_internal with second long double
argument negated.
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Compiling gcc/testsuite/gcc.dg/split-*.c and others with -mcpu=power10
and linking with a non-pcrel libgcc results in crashes due to the
power10 pcrel code not having r2 set for the generic-morestack.c
functions called from __morestack. There is also a problem when
non-pcrel code calls a pcrel libgcc. See the patch comments.
A similar situation theoretically occurs with ELFv1 multi-toc
executables, when __morestack might be located in a different toc
group to its caller. This patch makes no attempt to fix that, since
the gold linker does not support multi-toc (gold is needed for proper
support of -fsplit-stack code) nor does gcc emit __morestack calls
that support multi-toc.
* config/rs6000/morestack.S (R2_SAVE): Define.
(__morestack): Save and restore r2. Set up r2 for called
functions.
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The recent float128 ISA3.1 support (r12-1340) has some typos,
it makes the libgcc build fail if it's with one binutils
(assembler) which doesn't support Power10 insns. The error
looks like:
Error: invalid switch -mpower10
Error: unrecognized option -mpower10
... [...libgcc/shared-object.mk:14: float128-p10.o] Error 1
What this patch does are:
- fix test target typo libgcc_cv_powerpc_3_1_float128_hw
(written wrongly as libgcc_cv_powerpc_float128_hw, so it's
going to build ISA3.1 stuffs just when detecting ISA3.0).
- fix test used for libgcc_cv_powerpc_3_1_float128_hw check.
- fix test option used for libgcc_cv_powerpc_3_1_float128_hw
check.
- remove the ISA3.1 related contents from t-float128-hw.
- add new macro FLOAT128_HW_INSNS_ISA3_1 to differentiate
ISA3.1 content from ISA3.0 part in ifunc support.
Bootstrapped/regtested on:
- powerpc64le-linux-gnu P10
- powerpc64le-linux-gnu P9 (w/i and w/o p10 supported as)
- powerpc64-linux-gnu P8 (w/i and w/o p10 supported as)
libgcc/ChangeLog:
* configure: Regenerate.
* configure.ac (test for libgcc_cv_powerpc_3_1_float128_hw): Fix
typos among the name, CFLAGS and the test.
* config/rs6000/t-float128-hw (fp128_3_1_hw_funcs, fp128_3_1_hw_src,
fp128_3_1_hw_static_obj, fp128_3_1_hw_shared_obj, fp128_3_1_hw_obj):
Remove.
* config/rs6000/t-float128-p10-hw (FLOAT128_HW_INSNS): Append
macro FLOAT128_HW_INSNS_ISA3_1.
(FP128_3_1_CFLAGS_HW): Fix option typo.
* config/rs6000/float128-ifunc.c (SW_OR_HW_ISA3_1): Guard this with
FLOAT128_HW_INSNS_ISA3_1.
(__floattikf_resolve): Likewise.
(__floatuntikf_resolve): Likewise.
(__fixkfti_resolve): Likewise.
(__fixunskfti_resolve): Likewise.
(__floattikf): Likewise.
(__floatuntikf): Likewise.
(__fixkfti): Likewise.
(__fixunskfti): Likewise.
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The *TItype_ppc definitions are guarded by _ARCH_PPC64, so all
declarations using it should do so as well.
2021-06-10 Segher Boessenkool <segher@kernel.crashing.org>
libgcc/
* config/rs6000/quad-float128.h: Guard all uses of [U]TItype_ppc by
_ARCH_PPC64 .
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The files fixkfti-sw.c and fixunskfti-sw.c are renamed versions of
fixkfti.c and fixunskfti.c respectively to do the conversions in software.
The function names in the files were updated with the rename as well as
some white spaces fixes. The file float128-p10.c contains the functions
for using the ISA 3.1 hardware instructions to perform the conversions.
2021-06-08 Carl Love <cel@us.ibm.com>
gcc/ChangeLog
* config/rs6000/rs6000.c (__fixkfti, __fixunskfti, __floattikf,
__floatuntikf): Names changed to __fixkfti_sw, __fixunskfti_sw,
__floattikf_sw, __floatuntikf_sw respectively.
* config/rs6000/rs6000.md (floatti<mode>2, floatunsti<mode>2,
fix_trunc<mode>ti2, fixuns_trunc<mode>ti2): Add
define_insn for mode IEEE 128.
gcc/testsuite/ChangeLog
* gcc.target/powerpc/fp128_conversions.c: New file.
* gcc.target/powerpc/int_128bit-runnable.c(vextsd2q,
vcmpuq, vcmpsq, vcmpequq, vcmpequq., vcmpgtsq, vcmpgtsq.
vcmpgtuq, vcmpgtuq.): Update scan-assembler-times.
(ppc_native_128bit): Remove dg-require-effective-target.
libgcc/ChangeLog
* config.host: Add if test and set for
libgcc_cv_powerpc_3_1_float128_hw.
* config/rs6000/fixkfti.c: Renamed to fixkfti-sw.c.
Change calls of __fixkfti to __fixkfti_sw.
* config/rs6000/fixunskfti.c: Renamed to fixunskfti-sw.c.
Change calls of __fixunskfti to __fixunskfti_sw.
* config/rs6000/float128-p10.c (__floattikf_hw,
__floatuntikf_hw, __fixkfti_hw, __fixunskfti_hw): New file.
* config/rs6000/float128-ifunc.c (SW_OR_HW_ISA3_1): New macro.
(__floattikf_resolve, __floatuntikf_resolve, __fixkfti_resolve,
__fixunskfti_resolve): Add resolve functions.
(__floattikf, __floatuntikf, __fixkfti, __fixunskfti): New functions.
* config/rs6000/float128-sed (floattitf, __floatuntitf,
__fixtfti, __fixunstfti): Add editor commands to change names.
* config/rs6000/float128-sed-hw (__floattitf,
__floatuntitf, __fixtfti, __fixunstfti): Add editor commands to
change names.
* config/rs6000/floattikf.c: Renamed to floattikf-sw.c.
* config/rs6000/floatuntikf.c: Renamed to floatuntikf-sw.c.
* config/rs6000/quad-float128.h (__floattikf_sw,
__floatuntikf_sw, __fixkfti_sw, __fixunskfti_sw, __floattikf_hw,
__floatuntikf_hw, __fixkfti_hw, __fixunskfti_hw, __floattikf,
__floatuntikf, __fixkfti, __fixunskfti): New extern declarations.
* config/rs6000/t-float128 (floattikf, floatuntikf,
fixkfti, fixunskfti): Remove file names from fp128_ppc_funcs.
(floattikf-sw, floatuntikf-sw, fixkfti-sw, fixunskfti-sw): Add
file names to fp128_ppc_funcs.
* config/rs6000/t-float128-hw(fp128_3_1_hw_funcs,
fp128_3_1_hw_src, fp128_3_1_hw_static_obj, fp128_3_1_hw_shared_obj,
fp128_3_1_hw_obj): Add variables for ISA 3.1 support.
* config/rs6000/t-float128-p10-hw: New file.
* configure: Update script for isa 3.1 128-bit float support.
* configure.ac: Add check for 128-bit float hardware support.
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Correctness and performance test programs used during development of
this project may be found in the attachment to:
https://www.mail-archive.com/gcc-patches@gcc.gnu.org/msg254210.html
Summary of Purpose
This patch to libgcc/libgcc2.c __divdc3 provides an
opportunity to gain important improvements to the quality of answers
for the default complex divide routine (half, float, double, extended,
long double precisions) when dealing with very large or very small exponents.
The current code correctly implements Smith's method (1962) [2]
further modified by c99's requirements for dealing with NaN (not a
number) results. When working with input values where the exponents
are greater than *_MAX_EXP/2 or less than -(*_MAX_EXP)/2, results are
substantially different from the answers provided by quad precision
more than 1% of the time. This error rate may be unacceptable for many
applications that cannot a priori restrict their computations to the
safe range. The proposed method reduces the frequency of
"substantially different" answers by more than 99% for double
precision at a modest cost of performance.
Differences between current gcc methods and the new method will be
described. Then accuracy and performance differences will be discussed.
Background
This project started with an investigation related to
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59714. Study of Beebe[1]
provided an overview of past and recent practice for computing complex
divide. The current glibc implementation is based on Robert Smith's
algorithm [2] from 1962. A google search found the paper by Baudin
and Smith [3] (same Robert Smith) published in 2012. Elen Kalda's
proposed patch [4] is based on that paper.
I developed two sets of test data by randomly distributing values over
a restricted range and the full range of input values. The current
complex divide handled the restricted range well enough, but failed on
the full range more than 1% of the time. Baudin and Smith's primary
test for "ratio" equals zero reduced the cases with 16 or more error
bits by a factor of 5, but still left too many flawed answers. Adding
debug print out to cases with substantial errors allowed me to see the
intermediate calculations for test values that failed. I noted that
for many of the failures, "ratio" was a subnormal. Changing the
"ratio" test from check for zero to check for subnormal reduced the 16
bit error rate by another factor of 12. This single modified test
provides the greatest benefit for the least cost, but the percentage
of cases with greater than 16 bit errors (double precision data) is
still greater than 0.027% (2.7 in 10,000).
Continued examination of remaining errors and their intermediate
computations led to the various tests of input value tests and scaling
to avoid under/overflow. The current patch does not handle some of the
rare and most extreme combinations of input values, but the random
test data is only showing 1 case in 10 million that has an error of
greater than 12 bits. That case has 18 bits of error and is due to
subtraction cancellation. These results are significantly better
than the results reported by Baudin and Smith.
Support for half, float, double, extended, and long double precision
is included as all are handled with suitable preprocessor symbols in a
single source routine. Since half precision is computed with float
precision as per current libgcc practice, the enhanced algorithm
provides no benefit for half precision and would cost performance.
Further investigation showed changing the half precision algorithm
to use the simple formula (real=a*c+b*d imag=b*c-a*d) caused no
loss of precision and modest improvement in performance.
The existing constants for each precision:
float: FLT_MAX, FLT_MIN;
double: DBL_MAX, DBL_MIN;
extended and/or long double: LDBL_MAX, LDBL_MIN
are used for avoiding the more common overflow/underflow cases. This
use is made generic by defining appropriate __LIBGCC2_* macros in
c-cppbuiltin.c.
Tests are added for when both parts of the denominator have exponents
small enough to allow shifting any subnormal values to normal values
all input values could be scaled up without risking overflow. That
gained a clear improvement in accuracy. Similarly, when either
numerator was subnormal and the other numerator and both denominator
values were not too large, scaling could be used to reduce risk of
computing with subnormals. The test and scaling values used all fit
within the allowed exponent range for each precision required by the C
standard.
Float precision has more difficulty with getting correct answers than
double precision. When hardware for double precision floating point
operations is available, float precision is now handled in double
precision intermediate calculations with the simple algorithm the same
as the half-precision method of using float precision for intermediate
calculations. Using the higher precision yields exact results for all
tested input values (64-bit double, 32-bit float) with the only
performance cost being the requirement to convert the four input
values from float to double. If double precision hardware is not
available, then float complex divide will use the same improved
algorithm as the other precisions with similar change in performance.
Further Improvement
The most common remaining substantial errors are due to accuracy loss
when subtracting nearly equal values. This patch makes no attempt to
improve that situation.
NOTATION
For all of the following, the notation is:
Input complex values:
a+bi (a= real part, b= imaginary part)
c+di
Output complex value:
e+fi = (a+bi)/(c+di)
For the result tables:
current = current method (SMITH)
b1div = method proposed by Elen Kalda
b2div = alternate method considered by Elen Kalda
new = new method proposed by this patch
DESCRIPTIONS of different complex divide methods:
NAIVE COMPUTATION (-fcx-limited-range):
e = (a*c + b*d)/(c*c + d*d)
f = (b*c - a*d)/(c*c + d*d)
Note that c*c and d*d will overflow or underflow if either
c or d is outside the range 2^-538 to 2^512.
This method is available in gcc when the switch -fcx-limited-range is
used. That switch is also enabled by -ffast-math. Only one who has a
clear understanding of the maximum range of all intermediate values
generated by an application should consider using this switch.
SMITH's METHOD (current libgcc):
if(fabs(c)<fabs(d) {
r = c/d;
denom = (c*r) + d;
e = (a*r + b) / denom;
f = (b*r - a) / denom;
} else {
r = d/c;
denom = c + (d*r);
e = (a + b*r) / denom;
f = (b - a*r) / denom;
}
Smith's method is the current default method available with __divdc3.
Elen Kalda's METHOD
Elen Kalda proposed a patch about a year ago, also based on Baudin and
Smith, but not including tests for subnormals:
https://gcc.gnu.org/legacy-ml/gcc-patches/2019-08/msg01629.html [4]
It is compared here for accuracy with this patch.
This method applies the most significant part of the algorithm
proposed by Baudin&Smith (2012) in the paper "A Robust Complex
Division in Scilab" [3]. Elen's method also replaces two divides by
one divide and two multiplies due to the high cost of divide on
aarch64. In the comparison sections, this method will be labeled
b1div. A variation discussed in that patch which does not replace the
two divides will be labeled b2div.
inline void improved_internal (MTYPE a, MTYPE b, MTYPE c, MTYPE d)
{
r = d/c;
t = 1.0 / (c + (d * r));
if (r != 0) {
x = (a + (b * r)) * t;
y = (b - (a * r)) * t;
} else {
/* Changing the order of operations avoids the underflow of r impacting
the result. */
x = (a + (d * (b / c))) * t;
y = (b - (d * (a / c))) * t;
}
}
if (FABS (d) < FABS (c)) {
improved_internal (a, b, c, d);
} else {
improved_internal (b, a, d, c);
y = -y;
}
NEW METHOD (proposed by patch) to replace the current default method:
The proposed method starts with an algorithm proposed by Baudin&Smith
(2012) in the paper "A Robust Complex Division in Scilab" [3]. The
patch makes additional modifications to that method for further
reductions in the error rate. The following code shows the #define
values for double precision. See the patch for #define values used
for other precisions.
#define RBIG ((DBL_MAX)/2.0)
#define RMIN (DBL_MIN)
#define RMIN2 (0x1.0p-53)
#define RMINSCAL (0x1.0p+51)
#define RMAX2 ((RBIG)*(RMIN2))
if (FABS(c) < FABS(d)) {
/* prevent overflow when arguments are near max representable */
if ((FABS (d) > RBIG) || (FABS (a) > RBIG) || (FABS (b) > RBIG) ) {
a = a * 0.5;
b = b * 0.5;
c = c * 0.5;
d = d * 0.5;
}
/* minimize overflow/underflow issues when c and d are small */
else if (FABS (d) < RMIN2) {
a = a * RMINSCAL;
b = b * RMINSCAL;
c = c * RMINSCAL;
d = d * RMINSCAL;
}
else {
if(((FABS (a) < RMIN) && (FABS (b) < RMAX2) && (FABS (d) < RMAX2)) ||
((FABS (b) < RMIN) && (FABS (a) < RMAX2) && (FABS (d) < RMAX2))) {
a = a * RMINSCAL;
b = b * RMINSCAL;
c = c * RMINSCAL;
d = d * RMINSCAL;
}
}
r = c/d; denom = (c*r) + d;
if( r > RMIN ) {
e = (a*r + b) / denom ;
f = (b*r - a) / denom
} else {
e = (c * (a/d) + b) / denom;
f = (c * (b/d) - a) / denom;
}
}
[ only presenting the fabs(c) < fabs(d) case here, full code in patch. ]
Before any computation of the answer, the code checks for any input
values near maximum to allow down scaling to avoid overflow. These
scalings almost never harm the accuracy since they are by 2. Values that
are over RBIG are relatively rare but it is easy to test for them and
allow aviodance of overflows.
Testing for RMIN2 reveals when both c and d are less than [FLT|DBL]_EPSILON.
By scaling all values by 1/EPSILON, the code converts subnormals to normals,
avoids loss of accuracy and underflows in intermediate computations
that otherwise might occur. If scaling a and b by 1/EPSILON causes either
to overflow, then the computation will overflow whatever method is used.
Finally, we test for either a or b being subnormal (RMIN) and if so,
for the other three values being small enough to allow scaling. We
only need to test a single denominator value since we have already
determined which of c and d is larger.
Next, r (the ratio of c to d) is checked for being near zero. Baudin
and Smith checked r for zero. This code improves that approach by
checking for values less than DBL_MIN (subnormal) covers roughly 12
times as many cases and substantially improves overall accuracy. If r
is too small, then when it is used in a multiplication, there is a
high chance that the result will underflow to zero, losing significant
accuracy. That underflow is avoided by reordering the computation.
When r is subnormal, the code replaces a*r (= a*(c/d)) with ((a/d)*c)
which is mathematically the same but avoids the unnecessary underflow.
TEST Data
Two sets of data are presented to test these methods. Both sets
contain 10 million pairs of complex values. The exponents and
mantissas are generated using multiple calls to random() and then
combining the results. Only values which give results to complex
divide that are representable in the appropriate precision after
being computed in quad precision are used.
The first data set is labeled "moderate exponents".
The exponent range is limited to -DBL_MAX_EXP/2 to DBL_MAX_EXP/2
for Double Precision (use FLT_MAX_EXP or LDBL_MAX_EXP for the
appropriate precisions.
The second data set is labeled "full exponents".
The exponent range for these cases is the full exponent range
including subnormals for a given precision.
ACCURACY Test results:
Note: The following accuracy tests are based on IEEE-754 arithmetic.
Note: All results reporteed are based on use of fused multiply-add. If
fused multiply-add is not used, the error rate increases, giving more
1 and 2 bit errors for both current and new complex divide.
Differences between using fused multiply and not using it that are
greater than 2 bits are less than 1 in a million.
The complex divide methods are evaluated by determining the percentage
of values that exceed differences in low order bits. If a "2 bit"
test results show 1%, that would mean that 1% of 10,000,000 values
(100,000) have either a real or imaginary part that differs from the
quad precision result by more than the last 2 bits.
Results are reported for differences greater than or equal to 1 bit, 2
bits, 8 bits, 16 bits, 24 bits, and 52 bits for double precision. Even
when the patch avoids overflows and underflows, some input values are
expected to have errors due to the potential for catastrophic roundoff
from floating point subtraction. For example, when b*c and a*d are
nearly equal, the result of subtraction may lose several places of
accuracy. This patch does not attempt to detect or minimize this type
of error, but neither does it increase them.
I only show the results for Elen Kalda's method (with both 1 and
2 divides) and the new method for only 1 divide in the double
precision table.
In the following charts, lower values are better.
current - current complex divide in libgcc
b1div - Elen Kalda's method from Baudin & Smith with one divide
b2div - Elen Kalda's method from Baudin & Smith with two divides
new - This patch which uses 2 divides
===================================================
Errors Moderate Dataset
gtr eq current b1div b2div new
====== ======== ======== ======== ========
1 bit 0.24707% 0.92986% 0.24707% 0.24707%
2 bits 0.01762% 0.01770% 0.01762% 0.01762%
8 bits 0.00026% 0.00026% 0.00026% 0.00026%
16 bits 0.00000% 0.00000% 0.00000% 0.00000%
24 bits 0% 0% 0% 0%
52 bits 0% 0% 0% 0%
===================================================
Table 1: Errors with Moderate Dataset (Double Precision)
Note in Table 1 that both the old and new methods give identical error
rates for data with moderate exponents. Errors exceeding 16 bits are
exceedingly rare. There are substantial increases in the 1 bit error
rates for b1div (the 1 divide/2 multiplys method) as compared to b2div
(the 2 divides method). These differences are minimal for 2 bits and
larger error measurements.
===================================================
Errors Full Dataset
gtr eq current b1div b2div new
====== ======== ======== ======== ========
1 bit 2.05% 1.23842% 0.67130% 0.16664%
2 bits 1.88% 0.51615% 0.50354% 0.00900%
8 bits 1.77% 0.42856% 0.42168% 0.00011%
16 bits 1.63% 0.33840% 0.32879% 0.00001%
24 bits 1.51% 0.25583% 0.24405% 0.00000%
52 bits 1.13% 0.01886% 0.00350% 0.00000%
===================================================
Table 2: Errors with Full Dataset (Double Precision)
Table 2 shows significant differences in error rates. First, the
difference between b1div and b2div show a significantly higher error
rate for the b1div method both for single bit errros and well
beyond. Even for 52 bits, we see the b1div method gets completely
wrong answers more than 5 times as often as b2div. To retain
comparable accuracy with current complex divide results for small
exponents and due to the increase in errors for large exponents, I
choose to use the more accurate method of two divides.
The current method has more 1.6% of cases where it is getting results
where the low 24 bits of the mantissa differ from the correct
answer. More than 1.1% of cases where the answer is completely wrong.
The new method shows less than one case in 10,000 with greater than
two bits of error and only one case in 10 million with greater than
16 bits of errors. The new patch reduces 8 bit errors by
a factor of 16,000 and virtually eliminates completely wrong
answers.
As noted above, for architectures with double precision
hardware, the new method uses that hardware for the
intermediate calculations before returning the
result in float precision. Testing of the new patch
has shown zero errors found as seen in Tables 3 and 4.
Correctness for float
=============================
Errors Moderate Dataset
gtr eq current new
====== ======== ========
1 bit 28.68070% 0%
2 bits 0.64386% 0%
8 bits 0.00401% 0%
16 bits 0.00001% 0%
24 bits 0% 0%
=============================
Table 3: Errors with Moderate Dataset (float)
=============================
Errors Full Dataset
gtr eq current new
====== ======== ========
1 bit 19.98% 0%
2 bits 3.20% 0%
8 bits 1.97% 0%
16 bits 1.08% 0%
24 bits 0.55% 0%
=============================
Table 4: Errors with Full Dataset (float)
As before, the current method shows an troubling rate of extreme
errors.
There very minor changes in accuracy for half-precision since the code
changes from Smith's method to the simple method. 5 out of 1 million
test cases show correct answers instead of 1 or 2 bit errors.
libgcc computes half-precision functions in float precision
allowing the existing methods to avoid overflow/underflow issues
for the allowed range of exponents for half-precision.
Extended precision (using x87 80-bit format on x86) and Long double
(using IEEE-754 128-bit on x86 and aarch64) both have 15-bit exponents
as compared to 11-bit exponents in double precision. We note that the
C standard also allows Long Double to be implemented in the equivalent
range of Double. The RMIN2 and RMINSCAL constants are selected to work
within the Double range as well as with extended and 128-bit ranges.
We will limit our performance and accurancy discussions to the 80-bit
and 128-bit formats as seen on x86 here.
The extended and long double precision investigations were more
limited. Aarch64 does not support extended precision but does support
the software implementation of 128-bit long double precision. For x86,
long double defaults to the 80-bit precision but using the
-mlong-double-128 flag switches to using the software implementation
of 128-bit precision. Both 80-bit and 128-bit precisions have the same
exponent range, with the 128-bit precision has extended mantissas.
Since this change is only aimed at avoiding underflow/overflow for
extreme exponents, I studied the extended precision results on x86 for
100,000 values. The limited exponent dataset showed no differences.
For the dataset with full exponent range, the current and new values
showed major differences (greater than 32 bits) in 567 cases out of
100,000 (0.56%). In every one of these cases, the ratio of c/d or d/c
(as appropriate) was zero or subnormal, indicating the advantage of
the new method and its continued correctness where needed.
PERFORMANCE Test results
In order for a library change to be practical, it is necessary to show
the slowdown is tolerable. The slowdowns observed are much less than
would be seen by (for example) switching from hardware double precison
to a software quad precision, which on the tested machines causes a
slowdown of around 100x).
The actual slowdown depends on the machine architecture. It also
depends on the nature of the input data. If underflow/overflow is
rare, then implementations that have strong branch prediction will
only slowdown by a few cycles. If underflow/overflow is common, then
the branch predictors will be less accurate and the cost will be
higher.
Results from two machines are presented as examples of the overhead
for the new method. The one labeled x86 is a 5 year old Intel x86
processor and the one labeled aarch64 is a 3 year old arm64 processor.
In the following chart, the times are averaged over a one million
value data set. All values are scaled to set the time of the current
method to be 1.0. Lower values are better. A value of less than 1.0
would be faster than the current method and a value greater than 1.0
would be slower than the current method.
================================================
Moderate set full set
x86 aarch64 x86 aarch64
======== =============== ===============
float 0.59 0.79 0.45 0.81
double 1.04 1.24 1.38 1.56
long double 1.13 1.24 1.29 1.25
================================================
Table 5: Performance Comparisons (ratio new/current)
The above tables omit the timing for the 1 divide and 2 multiply
comparison with the 2 divide approach.
The float results show clear performance improvement due to using the
simple method with double precision for intermediate calculations.
The double results with the newer method show less overhead for the
moderate dataset than for the full dataset. That's because the moderate
dataset does not ever take the new branches which protect from
under/overflow. The better the branch predictor, the lower the cost
for these untaken branches. Both platforms are somewhat dated, with
the x86 having a better branch predictor which reduces the cost of the
additional branches in the new code. Of course, the relative slowdown
may be greater for some architectures, especially those with limited
branch prediction combined with a high cost of misprediction.
The long double results are fairly consistent in showing the moderate
additional cost of the extra branches and calculations for all cases.
The observed cost for all precisions is claimed to be tolerable on the
grounds that:
(a) the cost is worthwhile considering the accuracy improvement shown.
(b) most applications will only spend a small fraction of their time
calculating complex divide.
(c) it is much less than the cost of extended precision
(d) users are not forced to use it (as described below)
Those users who find this degree of slowdown unsatisfactory may use
the gcc switch -fcx-fortran-rules which does not use the library
routine, instead inlining Smith's method without the C99 requirement
for dealing with NaN results. The proposed patch for libgcc complex
divide does not affect the code generated by -fcx-fortran-rules.
SUMMARY
When input data to complex divide has exponents whose absolute value
is less than half of *_MAX_EXP, this patch makes no changes in
accuracy and has only a modest effect on performance. When input data
contains values outside those ranges, the patch eliminates more than
99.9% of major errors with a tolerable cost in performance.
In comparison to Elen Kalda's method, this patch introduces more
performance overhead but reduces major errors by a factor of
greater than 4000.
REFERENCES
[1] Nelson H.F. Beebe, "The Mathematical-Function Computation Handbook.
Springer International Publishing AG, 2017.
[2] Robert L. Smith. Algorithm 116: Complex division. Commun. ACM,
5(8):435, 1962.
[3] Michael Baudin and Robert L. Smith. "A robust complex division in
Scilab," October 2012, available at http://arxiv.org/abs/1210.4539.
[4] Elen Kalda: Complex division improvements in libgcc
https://gcc.gnu.org/legacy-ml/gcc-patches/2019-08/msg01629.html
2020-12-08 Patrick McGehearty <patrick.mcgehearty@oracle.com>
gcc/c-family/
* c-cppbuiltin.c (c_cpp_builtins): Add supporting macros for new
complex divide
libgcc/
* libgcc2.c (XMTYPE, XCTYPE, RBIG, RMIN, RMIN2, RMINSCAL, RMAX2):
Define.
(__divsc3, __divdc3, __divxc3, __divtc3): Improve complex divide.
* config/rs6000/_divkc3.c (RBIG, RMIN, RMIN2, RMINSCAL, RMAX2):
Define.
(__divkc3): Improve complex divide.
gcc/testsuite/
* gcc.c-torture/execute/ieee/cdivchkd.c: New test.
* gcc.c-torture/execute/ieee/cdivchkf.c: Likewise.
* gcc.c-torture/execute/ieee/cdivchkld.c: Likewise.
|
|
The test in the PowerPC 32-bit trampoline support is backwards. It aborts
if the trampoline size is greater than the expected size. It should abort
when the trampoline size is less than the expected size. I fixed the test
so the operands are reversed. I then folded the load immediate into the
compare instruction.
I verified this by creating a 32-bit trampoline program and manually
changing the size of the trampoline to be 48 instead of 40. The program
aborted with the larger size. I updated this code and ran the test again
and it passed.
I added a test case that runs on PowerPC 32-bit Linux systems and it calls
the __trampoline_setup function with a larger buffer size than the
compiler uses. The test is not run on 64-bit systems, since the function
__trampoline_setup is not called. I also limited the test to just Linux
systems, in case trampolines are handled differently in other systems.
libgcc/
2021-04-23 Michael Meissner <meissner@linux.ibm.com>
PR target/98952
* config/rs6000/tramp.S (__trampoline_setup, elfv1 #ifdef): Fix
trampoline size comparison in 32-bit by reversing test and
combining load immediate with compare.
(__trampoline_setup, elfv2 #ifdef): Fix trampoline size comparison
in 32-bit by reversing test and combining load immediate with
compare.
gcc/testsuite/
2021-04-23 Michael Meissner <meissner@linux.ibm.com>
PR target/98952
* gcc.target/powerpc/pr98952.c: New test.
|
|
This patch fixes the problem that the Decimal <-> Float128 conversions
were built even if the user configured GCC with --disable-decimal-float.
libgcc/
2021-04-05 Florian Weimer <fweimer@redhat.com>
* config/rs6000/t-float128 (fp128_ppc_funcs): Add decimal floating
point functions for $(decimal_float) only.
Co-Authored-By: Michael Meissner <meissner@linux.ibm.com>
|
|
[PR97653]
__floatunditf and __fixtfdi and a couple of other libgcc{.a,_s.so}
entrypoints for backwards compatibility should mean IBM double double
handling (i.e. IFmode), gcc emits such calls for that format and
form IEEE long double emits *kf* instead.
When gcc is configured without --with-long-double-format=ieee ,
everything is fine, but when it is not, we need to compile those
libgcc sources with -mno-gnu-attribute -mabi=ibmlongdouble.
The following snippet in libgcc/config/rs6000/t-linux was attempting
to ensure that, and for some routines it works fine (e.g. for _powitf2).
But, due to 4 different types of bugs it doesn't work for most of those
functions, which means that in --with-long-double-format=ieee
configured gcc those *tf* entrypoints instead handle the long double
arguments as if they were KFmode.
The bugs are:
1) the first few objs properly use $(objext) as suffix, but
several other contain a typo and use $(object) instead,
which is a variable that isn't set to anything, so we don't
add .o etc. extensions
2) while unsigned fix are properly called _fixuns*, unsigned float
are called _floatun* (without s), but the var was using there
the extra s and so didn't match
3) the variable didn't cover any of the TF <-> TI conversions,
only TF <-> DI conversions
4) nothing in libgcc_s.so was handled, as those object files are
called *_s.o rather than *.o and IBM128_SHARED_OBJS used wrong
syntax of the GNU make substitution reference, which should be
$(var:a=b) standing for $(patsubst a,b,$(var)) but it used
$(var:a:b) instead
2021-04-03 Jakub Jelinek <jakub@redhat.com>
PR target/97653
* config/rs6000/t-linux (IBM128_STATIC_OBJS): Fix spelling, use
$(objext) instead of $(object). Use _floatunditf instead of
_floatunsditf. Add tf <-> ti conversion objects.
(IBM128_SHARED_OBJS): Use proper substitution reference syntax.
|
|
In the patch that I applied on March 2nd, I had code to provide support for
Decimal/_Float128 conversions if the user did not use at least GLIBC 2.32. It
did this by using __ibm128 as an intermediate type. The trouble is __ibm128
cannot represent all of the numbers that _Float128 can, and you lose if you do
this conversion.
This patch removes this support. The dfp-bit.c functions now call the the
__sprintfieee128 and __strtoieee128 functions to do the conversion. If the
user does not have GLIBC, they will get a linker error that these functions do
not exist.
The float128 support functions are only built into the static libgcc, so there
isn't an issue with having references to __strtoieee128 and __sprintfieee128
with older GLIBC libraries.
As an added bonus, this patch eliminates the __sprintfkf function which
included stdio.h to get a definition for the sprintf library function. This
allows for building cross compilers without having to have a target stdio.h
available.
libgcc/
2021-03-29 Michael Meissner <meissner@linux.ibm.com>
* config/rs6000/t-float128 (fp128_decstr_funcs): Delete.
(fp128_ppc_funcs): Do not add $(fp128_decstr_funcs).
(fp128_decstr_objs): Delete.
* dfp-bit.h: Call __sprintfieee128 to do conversions from
_Float128 to a Decimal type. Call __strtoieee128 to do
conversions from a Decimal type to _Float128.
* config/rs6000/_sprintfkf.c: Delete file.
* config/rs6000/_sprintfkf.h: Delete file.
* config/rs6000/_strtokf.c: Delete file.
* config/rs6000/_strtokf.h: Delete file.
|
|
The prototype of __sprintfkf in _sprintfkf.h did not match the function in
_sprintfkf.c. This patch fixes the prototype. I also included the
_sprintfkf.h file in _sprintfkf.c to make sure the prototype is correct and to
eliminate a warning about declaring the function without a previous
declaration.
libgcc/
2021-03-01 Michael Meissner <meissner@linux.ibm.com>
* config/rs6000/_sprintfkf.h (__sprintfkf): Fix prototype to match
the function.
* config/rs6000/_sprintfkf.c: Include _sprintfkf.h.
|
|
This patch implements conversions between _Float128 and the 3 Decimal floating
types. It does this by extendending the dfp-bit conversions to add a new
binary floating point type (KF), and doing the conversions in the same manner
as the other binary/decimal conversions.
For conversions from _Float128 to Decimal, this patch uses a function
(__sprintfkf) instead of the sprintf function to convert long double values to
strings. The __sprintfkf function determines if GLIBC 2.32 or newer is used
and calls the IEEE 128-bit version of sprintf (__sprintfieee128). If the GLIBC
is earlier than 2.32, the code will convert _Float128 to __ibm128 and then use
the normal sprintf to convert this value.
For conversions from Decimal to _Float128, this patch uses a function
(__strtokf) instead of strtold to convert the strings from the Decimal
conversion to long double. The __strtokf function determines if GLIBC 2.32 or
newer is used, and if it is, calls the IEEE 128-bit version (__strtoieee128).
If the GLIBC is earlier than 2.32, the code will call strtold and convert the
__ibm128 value to _Float128.
These functions will primarily be used if/when the default PowerPC long double
type is changed to IEEE 128-bit, but they could also be used if the user
explicitly converts _Float128 to/from a Decimal type.
libgcc/
2021-02-22 Michael Meissner <meissner@linux.ibm.com>
* config/rs6000/_dd_to_kf.c: New file.
* config/rs6000/_kf_to_dd.c: New file.
* config/rs6000/_kf_to_sd.c: New file.
* config/rs6000/_kf_to_td.c: New file.
* config/rs6000/_sd_to_kf.c: New file.
* config/rs6000/_sprintfkf.c: New file.
* config/rs6000/_sprintfkf.h: New file.
* config/rs6000/_strtokf.h: New file.
* config/rs6000/_strtokf.c: New file.
* config/rs6000/_td_to_kf.c: New file.
* config/rs6000/quad-float128.h: Add new declarations.
* config/rs6000/t-float128 (fp128_dec_funcs): New macro.
(fp128_decstr_funcs): New macro.
(ibm128_dec_funcs): New macro.
(fp128_ppc_funcs): Add the new conversions.
(fp128_dec_objs): Force Decimal <-> __float128 conversions to be
compiled with -mabi=ieeelongdouble.
(fp128_decstr_objs): Force __float128 <-> string conversions to be
compiled with -mabi=ibmlongdouble.
(ibm128_dec_objs): Force Decimal <-> __float128 conversions to be
compiled with -mabi=ieeelongdouble.
(FP128_CFLAGS_DECIMAL): New macro.
(IBM128_CFLAGS_DECIMAL): New macro.
* dfp-bit.c (DFP_TO_BFP): Add PowerPC _Float128 support.
(BFP_TO_DFP): Add PowerPC _Float128 support.
* dfp-bit.h (BFP_KIND): Add new binary floating point kind for
IEEE 128-bit floating point.
(DFP_TO_BFP): Add PowerPC _Float128 support.
(BFP_TO_DFP): Add PowerPC _Float128 support.
(BFP_SPRINTF): New macro.
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If you use a compiler with long double defaulting to 64-bit instead of 128-bit
with IBM extended double, you get linker warnings about mis-matches in the gnu
attributes for long double (PR libgcc/97543). Even if the compiler is
configured to have long double be 64 bit as the default with the configuration
option '--without-long-double-128' you get the warnings.
You also get the same issues if you use a compiler with long double defaulting
to IEEE 128-bit instead of IBM extended double (PR libgcc/97643).
The issue is the way libgcc.a/libgcc.so is built. Right now when building
libgcc under Linux, the long double size is set to 128-bits when building
libgcc. However, the gnu attributes are set, leading to the warnings.
One feature of the current GNU attribute implementation is if you have a shared
library (such as libgcc_s.so), the GNU attributes for the shared library is an
inclusive OR of all of the objects within the library. This means if any
object file that uses the -mlong-double-128 option and uses long double, the GNU
attributes for the library will indicate that it uses 128-bit IBM long
doubles. If you have a static library, you will get the warning only if you
actually reference an object file with the attribute set.
This patch does two things:
1) All of the object files that support IBM 128-bit long doubles
explicitly set the ABI to IBM extended double.
2) I turned off GNU attributes for building the shared library or for
building the IBM 128-bit long double support.
libgcc/
2020-12-03 Michael Meissner <meissner@linux.ibm.com>
PR libgcc/97543
PR libgcc/97643
* config/rs6000/t-linux (IBM128_STATIC_OBJS): New make variable.
(IBM128_SHARED_OBJS): New make variable.
(IBM128_OBJS): New make variable. Set all objects to use the
explicit IBM format, and disable gnu attributes.
(IBM128_CFLAGS): New make variable.
(gcc_s_compile): Add -mno-gnu-attribute to all shared library
modules.
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This patch retires ppc64-fp.c in favour of using
"LIB2_SIDITI_CONV_FUNCS = yes", which is a lot better solution than
having a copy of selected libgcc2.c functions.
* config/rs6000/t-ppc64-fp (LIB2ADD): Delete.
(LIB2_SIDITI_CONV_FUNCS): Define.
* config/rs6000/ppc64-fp.c: Delete file.
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Generate assembly with .localentry,1 functions using @notoc calls.
This patch makes libgcc.a asm look the same as power10 pcrel as far as
toc/notoc is concerned.
Otherwise calling between functions that advertise as using the TOC
and those that don't, will require linker call stubs in statically
linked code.
gcc/
* config/rs6000/ppc-asm.h: Support __PCREL__ code.
libgcc/
* config/rs6000/morestack.S,
* config/rs6000/tramp.S: Support __PCREL__ code.
libitm/
* config/powerpc/sjlj.S: Support __PCREL__ code.
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We've had this hack in the libgcc config to build libgcc with
-mcmodel=small for powerpc64 for a long time. It wouldn't be a bad
thing if someone who knows the multilib machinery well could arrange
for -mcmodel=small to be passed just for ppc64 when building for
earlier than power10. But for now, make -mno-minimal-toc do nothing
when pcrel. Which will do the right thing for any project that has
copied libgcc's trick.
We want this if configuring using --with-cpu=power10 to build a
power10 pcrel libgcc. --mcmodel=small turns off pcrel.
gcc/
* config/rs6000/linux64.h (SUBSUBTARGET_OVERRIDE_OPTIONS): Don't
set -mcmodel=small for -mno-minimal-toc when pcrel.
libgcc/
* config/rs6000/t-linux: Document purpose of -mno-minimal-toc.
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AIX FAT libraries should be built with the version of AR chosen by configure.
The GNU Make $(AR) variable includes the AIX -X32_64 option needed
by the default Makefile rules to accept both 32 bit and 64 bit object files.
The -X32_64 option conflicts with ar archiving objects of the same name
used to build FAT libraries.
This patch changes the Makefile fragments for AIX FAT libraries to use $(AR),
but strips the -X32_64 option from the Make variable.
libgcc/ChangeLog:
2020-09-27 Clement Chigot <clement.chigot@atos.net>
* config/rs6000/t-slibgcc-aix: Use $(AR) without -X32_64.
libatomic/ChangeLog:
2020-09-27 Clement Chigot <clement.chigot@atos.net>
* config/t-aix: Use $(AR) without -X32_64.
libgomp/ChangeLog:
2020-09-27 Clement Chigot <clement.chigot@atos.net>
* config/t-aix: Use $(AR) without -X32_64.
libstdc++-v3/ChangeLog:
2020-09-27 Clement Chigot <clement.chigot@atos.net>
* config/os/aix/t-aix: Use $(AR) without -X32_64.
libgfortran/ChangeLog:
2020-09-27 Clement Chigot <clement.chigot@atos.net>
* config/t-aix: Use $(AR) without -X32_64.
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The FAT libraries config fragments need to know which library is native
and which is a multilib to choose the correct multilib from which to
append the additional object file or shared object file. Testing the
top-level archive is fragile because it will fail if rebuilding. This
patch tests the compiler preprocessing macros for the 64 bit AIX specific
__64BIT__ to determine the native mode of the compiler in MULTILIBTOP.
2020-07-14 David Edelsohn <dje.gcc@gmail.com>
libatomic/ChangeLog
* config/t-aix: Set BITS from compiler cpp macro.
libgcc/ChangeLog
* config/rs6000/t-slibgcc-aix: Set BITS from compiler cpp macro.
libgfortran/ChangeLog
* config/t-aix: Set BITS from compiler cpp macro.
libgomp/ChangeLog
* config/t-aix: Set BITS from compiler cpp macro.
libstdc++-v3/ChangeLog
* config/os/aix/t-aix: Set BITS from compiler cpp macro.
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This patch adds the ability to configure GCC on AIX to build as a
64 bit application and to build target libraries "FAT" libraries in both
32 bit and 64 bit mode.
The patch adds makefile fragment hooks to target libraries that allows
them to include target-specific rules. The target specific rules for
AIX place both 32 bit and 64 bit objects and shared objects
in archives at the top-level, not multilib subdirectories. The
multilibs are built in subdirectories, but must be combined during the
last parts of the target library build process. Because of the way
that GCC bootstrap works, the libraries must be combined during the
multiple stages of GCC bootstrap, not solely when installed in the
final destination, so the libraries are correct at the end of
each target library build stage, not solely an install recipe.
gcc/ChangeLog
2020-06-21 David Edelsohn <dje.gcc@gmail.com>
* config.gcc: Use t-aix64, biarch64 and default64 for cpu_is_64bit.
* config/rs6000/aix72.h (ASM_SPEC): Remove aix64 option.
(ASM_SPEC32): New.
(ASM_SPEC64): New.
(ASM_CPU_SPEC): Remove vsx and altivec options.
(CPP_SPEC_COMMON): Rename from CPP_SPEC.
(CPP_SPEC32): New.
(CPP_SPEC64): New.
(CPLUSPLUS_CPP_SPEC): Rename to CPLUSPLUS_CPP_SPEC_COMMON..
(TARGET_DEFAULT): Only define if not BIARCH.
(LIB_SPEC_COMMON): Rename from LIB_SPEC.
(LIB_SPEC32): New.
(LIB_SPEC64): New.
(LINK_SPEC_COMMON): Rename from LINK_SPEC.
(LINK_SPEC32): New.
(LINK_SPEC64): New.
(STARTFILE_SPEC): Add 64 bit version of crtcxa and crtdbase.
(ASM_SPEC): Define 32 and 64 bit alternatives using DEFAULT_ARCH64_P.
(CPP_SPEC): Same.
(CPLUSPLUS_CPP_SPEC): Same.
(LIB_SPEC): Same.
(LINK_SPEC): Same.
(SUBTARGET_EXTRA_SPECS): Add new 32/64 specs.
* config/rs6000/defaultaix64.h: New file.
* config/rs6000/t-aix64: New file.
libgcc/ChangeLog
2020-06-21 David Edelsohn <dje.gcc@gmail.com>
* config.host (extra_parts): Add crtcxa_64 and crtdbase_64.
* config/rs6000/t-aix-cxa: Explicitly compile 32 bit with -maix32
and 64 bit with -maix64.
* config/rs6000/t-slibgcc-aix: Remove extra @multilib_dir@ level.
Build and install AIX-style FAT libraries.
libgomp/ChangeLog
2020-06-21 David Edelsohn <dje.gcc@gmail.com>
* Makefile.am (tmake_file): Build and install AIX-style FAT libraries.
* Makefile.in: Regenerate
* configure.ac (tmake_file): Substitute.
* configure: Regenerate.
* configure.tgt (powerpc-ibm-aix*): Define tmake_file.
* config/t-aix: New file.
libstdc++-v3/ChangeLog
2020-06-21 David Edelsohn <dje.gcc@gmail.com>
* Makefile.am (tmake_file): Build and install AIX-style FAT libraries.
* Makefile.in: Regenerate.
* configure.ac (tmake_file): Substitute.
* configure: Regenerate.
* configure.host (aix*): Define tmake_file.
* config/os/aix/t-aix: New file.
libatomic/ChangeLog
2020-06-21 David Edelsohn <dje.gcc@gmail.com>
* Makefile.am (tmake_file): Build and install AIX-style FAT libraries.
* Makefile.in: Regenerate.
* configure.ac (tmake_file): Substitute.
* configure: Regenerate.
* configure.tgt (powerpc-ibm-aix*): Define tmake_file.
* config/t-aix: New file.
libgfortran/ChangeLog
2020-06-21 David Edelsohn <dje.gcc@gmail.com>
* Makefile.am (tmake_file): Build and install AIX-style FAT libraries.
* Makefile.in: Regenerate.
* configure.ac (tmake_file): Substitute.
* configure: Regenerate.
* configure.host: Add system configury stanza. Define tmake_file.
* config/t-aix: New file.
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2020-05-05 Michael Meissner <meissner@linux.ibm.com>
* config/rs6000/rs6000-builtin.def: Delete changes meant for a
private branch.
* config/rs6000/rs6000-c.c: Likewise.
* config/rs6000/rs6000-call.c: Likewise.
* gcc/config/rs6000/rs6000.c: Likewise.
2020-05-05 Michael Meissner <meissner@linux.ibm.com>
* gcc.dg/nextafter-2.c: Delete changes meant for a private branch.
* gcc.target/powerpc/pr70117.c: Likewise.
2020-05-05 Michael Meissner <meissner@linux.ibm.com>
* config.host: Delete changes meant for a private branch.
* config/rs6000/t-float128: Likewise.
* configure.ac: Likewise.
* configure: Likewise.
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Since commit e154242724b084380e3221df7c08fcdbd8460674 the flag -many is
sometimes not passed to the assembler. Use .machine ppc to prevent
errors if these files are assembled for an ISA which does not support
FPRs.
libgcc/
* config/rs6000/crtresfpr.S: Use .machine ppc.
* config/rs6000/crtresxfpr.S: Likewise.
* config/rs6000/crtsavfpr.S: Likewise.
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From-SVN: r279813
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The library handling and some of the options for creating the crts for
the older PPC Darwin versions had bit-rotted somewhat. This adjusts the
build criteria for the crts to avoid newer ld64 versions warnings about
mismatches in build and object versions.
Added to some of the comments that it's documented why the specs are as
they are.
2019-07-03 Iain Sandoe <iain@sandoe.co.uk>
gcc/
* config/darwin.h (REAL_LIBGCC_SPEC): Adjust for earlier Darwin.
(STARTFILE_SPEC): Split crt3 into a separate spec.
(DARWIN_EXTRA_SPECS): Add crt2 and crt3 spec.
(DARWIN_CRT2_SPEC): New.
(DARWIN_CRT3_SPEC): New.
(MIN_LD64_OMIT_STUBS): Revise to 62.1.
* config/rs6000/darwin.h (DARWIN_CRT2_SPEC): Revise conditions.
(DARWIN_CRT3_SPEC): New.
libgcc/
2019-07-03 Iain Sandoe <iain@sandoe.co.uk>
* config.host (powerpc-*-darwin*,powerpc64-*-darwin*): Revise crt
list.
* config/rs6000/t-darwin: Build crt3_2 for older systems. Revise
mmacosx-version-min for crts to run across all system versions.
* config/rs6000/t-darwin64 (LIB2ADD): Remove.
* config/t-darwin: Revise mmacosx-version-min for crts to run across
system versions >= 10.4.
From-SVN: r273016
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We have been including this in libgcc, which means that we have to append
-lgcc even when using shared libgcc. In preparation for revision of libgcc
split this into an endfile.
gcc/
2019-06-25 Iain Sandoe <iain@sandoe.co.uk>
* config/rs6000/darwin.h (ENDFILE_SPEC): New.
libgcc/
2019-06-25 Iain Sandoe <iain@sandoe.co.uk>
* config.host: Add libef_ppc.a to the extra files for powerpc-darwin.
* config/rs6000/t-darwin: (PPC_ENDFILE_SRC, PPC_ENDFILE_OBJS): New.
Build objects for the out of line save/restore register functions
so that they can be used for any supported Darwin version.
* config/t-darwin: Default the build Darwin version to Darwin8
(MacOS 10.4).
From-SVN: r272659
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When libgcc is built on Darwin, it is usually built for the earliest potential
target (Darwin8, 10.4). Build for that revision default to assuming that the
processor might be G3 (without vector ops) and there is an outlined function
used for save/restore that checks whether the processor is G3 or G4+ at run-
time. However, the unwinder itself needs to be built with the assumption of
vector usage so that the relevant outlined functions are called.
2019-06-06 Iain Sandoe <iain@sandoe.co.uk>
* config/rs6000/t-darwin: Ensure that the unwinder is built with
altivec enabled.
From-SVN: r272017
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* config/rs6000/aix-unwind.h (LR_REGNO): Rename to R_LR.
(CR2_REGNO): Rename to R_CR2.
(XER_REGNO): Rename to R_XER.
(FIRST_ALTIVEC_REGNO): Rename to R_FIRST_ALTIVEC.
(VRSAVE_REGNO): Rename to R_VRSAVE.
(VSCR_REGNO): R_VSCR.
From-SVN: r271967
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This patch is updating all soft-fp from glibc, most changes are
copyright years update, and changes other than years update are
* soft-fp/extenddftf2.c: Use "_FP_W_TYPE_SIZE < 64" to check if
4_FP_W_TYPEs are used for IEEE quad precision.
* soft-fp/extendhftf2.c: Likewise.
* soft-fp/extendsftf2.c: Likewise.
* soft-fp/extendxftf2.c: Likewise.
* soft-fp/trunctfdf2.c: Likewise.
* soft-fp/trunctfhf2.c: Likewise.
* soft-fp/trunctfsf2.c: Likewise.
* soft-fp/trunctfxf2.c: Likewise.
* config/rs6000/ibm-ldouble.c: Likewise.
From-SVN: r271327
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The asm file fails to build if we use a modern assembler
which checks that the machine is consistent with the
filetype. Fixed by adjusting in a similar manner to
other assembler.
libgcc/
2019-05-12 Iain Sandoe <iain@sandoe.co.uk>
* config/rs6000/darwin-vecsave.S: Set .machine appropriately.
From-SVN: r271111
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From-SVN: r267494
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Currently, .cfi_endproc and FUNC_END(__trampoline_setup) are placed
inside the #else branch of an "#if defined (__VXWORKS__) ...", so
non-pic vxworks does not get proper CFI nor a .size directive for
__trampoline_setup. I assume there's no magic reason for that (which
would warrant a comment), so move them outside.
From-SVN: r267051
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There are a few places in libgcc assembly where we don't emit call
frame information for functions, potentially breaking unwinding from
asynchronous signal handlers. This patch fixes them. Although I
patch tramp.S there is no attempt made to provide CFI for the actual
trampoline on the stack. Doing that would require generating CFI at
run time and both registering and deregistering it, which is probably
not worth doing since it would significantly slow down the call.
* config/rs6000/morestack.S (__stack_split_initialize),
(__morestack_get_guard, __morestack_set_guard),
(__morestack_make_guard): Provide CFI covering these functions.
* config/rs6000/tramp.S (__trampoline_setup): Likewise.
From-SVN: r266503
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2018-10-12 Olivier Hainque <hainque@adacore.com>
* config/rs6000/ibm-ldouble.c: Augment the toplevel guard with
defined (__FLOAT128_TYPE__) || defined (__LONG_DOUBLE_128__).
From-SVN: r265135
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