On Tue, Jun 17, 2025 at 10:04 PM Cui, Lili <lili....@intel.com> wrote:
>
> From: Lili Cui <lili....@intel.com>
>
> Hi Uros,
>
> This is patch v3, the main changes are as follows.
>
> 1. Added a pro_epilogue_adjust_stack_add_nocc in i386.md to add memory
> clobber for lea/mov.
> 2. Adjusted some formatting issues.
> 3. Added scan-rtl-dumps for ia32 in shrink_wrap_separate.C.
>
> Collected spec2017 performance on ZNVER5, EMR and ICELAKE. No performance
> regression was observed.
> For O2 multi-copy :
> 511.povray_r improved by 2.8% on ZNVER5.
> 511.povray_r improved by 4.2% on EMR
>
> Bootstrapped & regtested on x86-64-pc-linux-gnu.
> Use this patch to build the latest Linux kernel and boot successfully.
>
> Thanks,
> Lili.
>
>
> This commit implements the target macros (TARGET_SHRINK_WRAP_*) that
> enable separate shrink wrapping for function prologues/epilogues in
> x86.
>
> When performing separate shrink wrapping, we choose to use mov instead
> of push/pop, because using push/pop is more complicated to handle rsp
> adjustment and may lose performance, so here we choose to use mov, which
> has a small impact on code size, but guarantees performance.
>
> Using mov means we need to use sub/add to maintain the stack frame. In
> some special cases, we need to use lea to prevent affecting EFlags.
>
> Avoid inserting sub between test-je-jle to change EFlags, lea should be
> used here.
>
> foo:
> xorl %eax, %eax
> testl %edi, %edi
> je .L11
> sub $16, %rsp ------> leaq -16(%rsp), %rsp
> movq %r13, 8(%rsp)
> movl $1, %r13d
> jle .L4
>
> Tested against SPEC CPU 2017, this change always has a net-positive
> effect on the dynamic instruction count. See the following table for
> the breakdown on how this reduces the number of dynamic instructions
> per workload on a like-for-like (with/without this commit):
>
> instruction count base with commit (commit-base)/commit
> 502.gcc_r 98666845943 96891561634 -1.80%
> 526.blender_r 6.21226E+11 6.12992E+11 -1.33%
> 520.omnetpp_r 1.1241E+11 1.11093E+11 -1.17%
> 500.perlbench_r 1271558717 1263268350 -0.65%
> 523.xalancbmk_r 2.20103E+11 2.18836E+11 -0.58%
> 531.deepsjeng_r 2.73591E+11 2.72114E+11 -0.54%
> 500.perlbench_r 64195557393 63881512409 -0.49%
> 541.leela_r 2.99097E+11 2.98245E+11 -0.29%
> 548.exchange2_r 1.27976E+11 1.27784E+11 -0.15%
> 527.cam4_r 88981458425 88887334679 -0.11%
> 554.roms_r 2.60072E+11 2.59809E+11 -0.10%
>
> Collected spec2017 performance on ZNVER5, EMR and ICELAKE. No performance
> regression was observed.
>
> For O2 multi-copy :
> 511.povray_r improved by 2.8% on ZNVER5.
> 511.povray_r improved by 4% on EMR
> 511.povray_r improved by 3.3 % ~ 4.6% on ICELAKE.
>
> gcc/ChangeLog:
>
> * config/i386/i386-protos.h (ix86_get_separate_components):
> New function.
> (ix86_components_for_bb): Likewise.
> (ix86_disqualify_components): Likewise.
> (ix86_emit_prologue_components): Likewise.
> (ix86_emit_epilogue_components): Likewise.
> (ix86_set_handled_components): Likewise.
> * config/i386/i386.cc (save_regs_using_push_pop):
> Split from ix86_compute_frame_layout.
> (ix86_compute_frame_layout):
> Use save_regs_using_push_pop.
> (pro_epilogue_adjust_stack):
> Use gen_pro_epilogue_adjust_stack_add_nocc.
> (ix86_expand_prologue): Add some assertions and adjust
> the stack frame at the beginning of the prolog for shrink
> wrapping separate.
> (ix86_emit_save_regs_using_mov):
> Skip registers that are wrapped separately.
> (ix86_emit_restore_regs_using_mov): Likewise.
> (ix86_expand_epilogue): Add some assertions and set
> restore_regs_via_mov to true for shrink wrapping separate.
> (ix86_get_separate_components): New function.
> (ix86_components_for_bb): Likewise.
> (ix86_disqualify_components): Likewise.
> (ix86_emit_prologue_components): Likewise.
> (ix86_emit_epilogue_components): Likewise.
> (ix86_set_handled_components): Likewise.
> (TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS): Define.
> (TARGET_SHRINK_WRAP_COMPONENTS_FOR_BB): Likewise.
> (TARGET_SHRINK_WRAP_DISQUALIFY_COMPONENTS): Likewise.
> (TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS): Likewise.
> (TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS): Likewise.
> (TARGET_SHRINK_WRAP_SET_HANDLED_COMPONENTS): Likewise.
> * config/i386/i386.h (struct machine_function):Add
> reg_is_wrapped_separately array for register wrapping
> information.
> * config/i386/i386.md
> (@pro_epilogue_adjust_stack_add_nocc<mode>): New.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/x86_64/abi/callabi/leaf-2.c: Adjust the test.
> * gcc.target/i386/interrupt-16.c: Likewise.
> * gfortran.dg/guality/arg1.f90: Likewise.
> * gcc.target/i386/avx10_2-comibf-1.c: Likewise.
> * g++.target/i386/shrink_wrap_separate.C: New test.
> * gcc.target/i386/shrink_wrap_separate_check_lea.c: Likewise.
>
> Co-authored-by: Michael Matz <m...@suse.de>
> ---
> gcc/config/i386/i386-protos.h | 7 +
> gcc/config/i386/i386.cc | 332 +++++++++++++++---
> gcc/config/i386/i386.h | 4 +
> gcc/config/i386/i386.md | 22 ++
> .../g++.target/i386/shrink_wrap_separate.C | 25 ++
> .../gcc.target/i386/avx10_2-comibf-1.c | 2 +-
> gcc/testsuite/gcc.target/i386/interrupt-16.c | 4 +-
> .../i386/shrink_wrap_separate_check_lea.c | 29 ++
> .../gcc.target/x86_64/abi/callabi/leaf-2.c | 2 +-
> gcc/testsuite/gfortran.dg/guality/arg1.f90 | 2 +-
> 10 files changed, 379 insertions(+), 50 deletions(-)
> create mode 100644 gcc/testsuite/g++.target/i386/shrink_wrap_separate.C
> create mode 100644
> gcc/testsuite/gcc.target/i386/shrink_wrap_separate_check_lea.c
>
Hi Lili,
Your patch caused:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120840
The enclosed patch seemed to fix it. It looks like x86 separate
shrink wrapping
doesn't properly restore all registers when function with preserve_none or
no_callee_saved_registers is called. Can you find a run-time testcase and
fix it?
Thanks.
--
H.J.
diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
index 24b0a766265..b32d0228193 100644
--- a/gcc/config/i386/i386-expand.cc
+++ b/gcc/config/i386/i386-expand.cc
@@ -10393,6 +10393,8 @@ ix86_expand_call (rtx retval, rtx fnaddr, rtx callarg1,
&& !MMX_REGNO_P (i))
clobber_reg (&use,
gen_rtx_REG (GET_MODE (regno_reg_rtx[i]), i));
+
+ cfun->machine->call_preserve_none_p = true;
}
if (vec_len > 1)
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 0dad62b5374..7e35f1d772e 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -28242,6 +28242,7 @@ ix86_get_separate_components (void)
|| cfun->machine->func_type != TYPE_NORMAL
|| TARGET_SEH
|| crtl->stack_realign_needed
+ || m->call_preserve_none_p
|| m->call_ms2sysv)
return components;
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index 880fdbadd2f..a4240c66362 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -2932,6 +2932,10 @@ struct GTY(()) machine_function {
/* The largest alignment, in bytes, of stack slot actually used. */
unsigned int max_used_stack_alignment;
+ /* True if function with preserve_none/no_callee_saved_registers
+ attribute is called. */
+ BOOL_BITFIELD call_preserve_none_p : 1;
+
/* During prologue/epilogue generation, the current frame state.
Otherwise, the frame state at the end of the prologue. */
struct machine_frame_state fs;
