On Tue, May 13, 2025 at 8:15 AM Cui, Lili <[email protected]> wrote:
>
> From: Lili Cui <[email protected]>
>
> Hi,
>
> This patch is to enale separate shrink wrapping for x86.
>
> Bootstrapped & regtested on x86-64-pc-linux-gnu.
>
> Ok for trunk?
Unfortunately, the patched compiler fails to boot the latest linux kernel.
Uros.
Uros.
>
>
> 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.
>
> 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%
>
> 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):
> Encapsulate code.
> (ix86_compute_frame_layout):
> Handle save_regs_using_push_pop.
> (ix86_emit_save_regs_using_mov):
> Skip registers that are wrapped separately.
> (ix86_expand_prologue): Likewise.
> (ix86_emit_restore_regs_using_mov): Likewise.
> (ix86_expand_epilogue): Likewise.
> (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.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/x86_64/abi/callabi/leaf-2.c: Adjust the test.
> * gcc.target/i386/interrupt-16.c: Likewise.
> * g++.target/i386/shrink_wrap_separate.c: New test.
> ---
> gcc/config/i386/i386-protos.h | 7 +
> gcc/config/i386/i386.cc | 261 +++++++++++++++---
> gcc/config/i386/i386.h | 1 +
> .../g++.target/i386/shrink_wrap_separate.c | 24 ++
> gcc/testsuite/gcc.target/i386/interrupt-16.c | 4 +-
> .../gcc.target/x86_64/abi/callabi/leaf-2.c | 2 +-
> 6 files changed, 257 insertions(+), 42 deletions(-)
> create mode 100644 gcc/testsuite/g++.target/i386/shrink_wrap_separate.c
>
> diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h
> index e85b925704b..11d26e93973 100644
> --- a/gcc/config/i386/i386-protos.h
> +++ b/gcc/config/i386/i386-protos.h
> @@ -436,6 +436,13 @@ extern rtl_opt_pass *make_pass_align_tight_loops
> (gcc::context *);
> extern bool ix86_has_no_direct_extern_access;
> extern bool ix86_rpad_gate ();
>
> +extern sbitmap ix86_get_separate_components (void);
> +extern sbitmap ix86_components_for_bb (basic_block);
> +extern void ix86_disqualify_components (sbitmap, edge, sbitmap, bool);
> +extern void ix86_emit_prologue_components (sbitmap);
> +extern void ix86_emit_epilogue_components (sbitmap);
> +extern void ix86_set_handled_components (sbitmap);
> +
> /* In i386-expand.cc. */
> bool ix86_check_builtin_isa_match (unsigned int, HOST_WIDE_INT*,
> HOST_WIDE_INT*);
> diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
> index 3d629b06094..2e8485ddb8b 100644
> --- a/gcc/config/i386/i386.cc
> +++ b/gcc/config/i386/i386.cc
> @@ -6909,6 +6909,26 @@ ix86_pro_and_epilogue_can_use_push2pop2 (int nregs)
> && (nregs + aligned) >= 3;
> }
>
> +/* Check if push pop should be used to save registers. */
> +static bool
> +save_regs_using_push_pop (HOST_WIDE_INT to_allocate)
> +{
> + return ((!to_allocate && cfun->machine->frame.nregs <= 1)
> + || (TARGET_64BIT && to_allocate >= HOST_WIDE_INT_C (0x80000000))
> + /* If static stack checking is enabled and done with probes,
> + the registers need to be saved before allocating the frame. */
> + || flag_stack_check == STATIC_BUILTIN_STACK_CHECK
> + /* If stack clash probing needs a loop, then it needs a
> + scratch register. But the returned register is only guaranteed
> + to be safe to use after register saves are complete. So if
> + stack clash protections are enabled and the allocated frame is
> + larger than the probe interval, then use pushes to save
> + callee saved registers. */
> + || (flag_stack_clash_protection
> + && !ix86_target_stack_probe ()
> + && to_allocate > get_probe_interval ()));
> +}
> +
> /* Fill structure ix86_frame about frame of currently computed function. */
>
> static void
> @@ -7193,20 +7213,7 @@ ix86_compute_frame_layout (void)
> /* Size prologue needs to allocate. */
> to_allocate = offset - frame->sse_reg_save_offset;
>
> - if ((!to_allocate && frame->nregs <= 1)
> - || (TARGET_64BIT && to_allocate >= HOST_WIDE_INT_C (0x80000000))
> - /* If static stack checking is enabled and done with probes,
> - the registers need to be saved before allocating the frame. */
> - || flag_stack_check == STATIC_BUILTIN_STACK_CHECK
> - /* If stack clash probing needs a loop, then it needs a
> - scratch register. But the returned register is only guaranteed
> - to be safe to use after register saves are complete. So if
> - stack clash protections are enabled and the allocated frame is
> - larger than the probe interval, then use pushes to save
> - callee saved registers. */
> - || (flag_stack_clash_protection
> - && !ix86_target_stack_probe ()
> - && to_allocate > get_probe_interval ()))
> + if (save_regs_using_push_pop (to_allocate))
> frame->save_regs_using_mov = false;
>
> if (ix86_using_red_zone ()
> @@ -7664,7 +7671,9 @@ ix86_emit_save_regs_using_mov (HOST_WIDE_INT cfa_offset)
> for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
> if (GENERAL_REGNO_P (regno) && ix86_save_reg (regno, true, true))
> {
> - ix86_emit_save_reg_using_mov (word_mode, regno, cfa_offset);
> + /* Skip shrink warp separate already processed registers. */
> + if (!cfun->machine->reg_is_wrapped_separately[regno])
> + ix86_emit_save_reg_using_mov (word_mode, regno, cfa_offset);
> cfa_offset -= UNITS_PER_WORD;
> }
> }
> @@ -9227,6 +9236,18 @@ ix86_expand_prologue (void)
> && (! TARGET_STACK_PROBE
> || frame.stack_pointer_offset < CHECK_STACK_LIMIT))
> {
> + HOST_WIDE_INT allocate_offset;
> + /* If shrink wrap separate works, we will adjust the total offset of
> + rsp at the beginning. */
> + if (crtl->shrink_wrapped_separate)
> + {
> + allocate_offset = m->fs.sp_offset - frame.stack_pointer_offset;
> + pro_epilogue_adjust_stack (stack_pointer_rtx, stack_pointer_rtx,
> + GEN_INT (allocate_offset), -1,
> + m->fs.cfa_reg == stack_pointer_rtx);
> + m->fs.sp_offset = cfun->machine->frame.stack_pointer_offset;
> + }
> +
> ix86_emit_save_regs_using_mov (frame.reg_save_offset);
> cfun->machine->red_zone_used = true;
> int_registers_saved = true;
> @@ -9806,30 +9827,36 @@ ix86_emit_restore_regs_using_mov (HOST_WIDE_INT
> cfa_offset,
> for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
> if (GENERAL_REGNO_P (regno) && ix86_save_reg (regno, maybe_eh_return,
> true))
> {
> - rtx reg = gen_rtx_REG (word_mode, regno);
> - rtx mem;
> - rtx_insn *insn;
> -
> - mem = choose_baseaddr (cfa_offset, NULL);
> - mem = gen_frame_mem (word_mode, mem);
> - insn = emit_move_insn (reg, mem);
>
> - if (m->fs.cfa_reg == crtl->drap_reg && regno == REGNO
> (crtl->drap_reg))
> + /* Skip shrink warp separate already processed registers. */
> + if (!cfun->machine->reg_is_wrapped_separately[regno])
> {
> - /* Previously we'd represented the CFA as an expression
> - like *(%ebp - 8). We've just popped that value from
> - the stack, which means we need to reset the CFA to
> - the drap register. This will remain until we restore
> - the stack pointer. */
> - add_reg_note (insn, REG_CFA_DEF_CFA, reg);
> - RTX_FRAME_RELATED_P (insn) = 1;
> + rtx reg = gen_rtx_REG (word_mode, regno);
> + rtx mem;
> + rtx_insn *insn;
>
> - /* This means that the DRAP register is valid for addressing. */
> - m->fs.drap_valid = true;
> - }
> - else
> - ix86_add_cfa_restore_note (NULL, reg, cfa_offset);
> + mem = choose_baseaddr (cfa_offset, NULL);
> + mem = gen_frame_mem (word_mode, mem);
> + insn = emit_move_insn (reg, mem);
>
> + if (m->fs.cfa_reg == crtl->drap_reg
> + && regno == REGNO (crtl->drap_reg))
> + {
> + /* Previously we'd represented the CFA as an expression
> + like *(%ebp - 8). We've just popped that value from
> + the stack, which means we need to reset the CFA to
> + the drap register. This will remain until we restore
> + the stack pointer. */
> + add_reg_note (insn, REG_CFA_DEF_CFA, reg);
> + RTX_FRAME_RELATED_P (insn) = 1;
> +
> + /* This means that the DRAP register is valid for addressing.
> + */
> + m->fs.drap_valid = true;
> + }
> + else
> + ix86_add_cfa_restore_note (NULL, reg, cfa_offset);
> + }
> cfa_offset -= UNITS_PER_WORD;
> }
> }
> @@ -10108,10 +10135,11 @@ ix86_expand_epilogue (int style)
> less work than reloading sp and popping the register. */
> else if (!sp_valid_at (frame.hfp_save_offset) && frame.nregs <= 1)
> restore_regs_via_mov = true;
> - else if (TARGET_EPILOGUE_USING_MOVE
> - && cfun->machine->use_fast_prologue_epilogue
> - && (frame.nregs > 1
> - || m->fs.sp_offset != reg_save_offset))
> + else if (crtl->shrink_wrapped_separate
> + || (TARGET_EPILOGUE_USING_MOVE
> + && cfun->machine->use_fast_prologue_epilogue
> + && (frame.nregs > 1
> + || m->fs.sp_offset != reg_save_offset)))
> restore_regs_via_mov = true;
> else if (frame_pointer_needed
> && !frame.nregs
> @@ -28065,6 +28093,161 @@ ix86_cannot_copy_insn_p (rtx_insn *insn)
> #undef TARGET_DOCUMENTATION_NAME
> #define TARGET_DOCUMENTATION_NAME "x86"
>
> +/* Implement TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS. */
> +sbitmap
> +ix86_get_separate_components (void)
> +{
> + HOST_WIDE_INT offset, to_allocate;
> + sbitmap components = sbitmap_alloc (FIRST_PSEUDO_REGISTER);
> + bitmap_clear (components);
> +
> + offset = cfun->machine->frame.stack_pointer_offset;
> + to_allocate = offset - cfun->machine->frame.sse_reg_save_offset;
> + /* When PPX is enabled, disable shrink wrap separate.
> + It is a trade-off. */
> + if (TARGET_APX_PPX && !crtl->calls_eh_return)
> + return components;
> +
> + /* Since shrink wrapping separate uses MOV instead of PUSH/POP
> + We need to disable shrink wrap separate when move is prohibited. */
> + if (save_regs_using_push_pop (to_allocate))
> + return components;
> +
> + for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
> + if (GENERAL_REGNO_P (regno) && ix86_save_reg (regno, true, true))
> + {
> + /* We can only wrap registers that have small operand offsets.
> + For large offsets a pseudo register might be needed which
> + cannot be created during the shrink wrapping pass. */
> + if (IN_RANGE (offset, -0x8000, 0x7fff))
> + bitmap_set_bit (components, regno);
> + offset += UNITS_PER_WORD;
> + }
> +
> + /* Don't mess with the following frame pointer. */
> + if (frame_pointer_needed)
> + bitmap_clear_bit (components, HARD_FRAME_POINTER_REGNUM);
> +
> + if (crtl->drap_reg)
> + bitmap_clear_bit (components, REGNO (crtl->drap_reg));
> +
> + if (pic_offset_table_rtx)
> + bitmap_clear_bit (components, REAL_PIC_OFFSET_TABLE_REGNUM);
> +
> + return components;
> +}
> +
> +/* Implement TARGET_SHRINK_WRAP_COMPONENTS_FOR_BB. */
> +sbitmap
> +ix86_components_for_bb (basic_block bb)
> +{
> + bitmap in = DF_LIVE_IN (bb);
> + bitmap gen = &DF_LIVE_BB_INFO (bb)->gen;
> + bitmap kill = &DF_LIVE_BB_INFO (bb)->kill;
> +
> + sbitmap components = sbitmap_alloc (FIRST_PSEUDO_REGISTER);
> + bitmap_clear (components);
> +
> + function_abi_aggregator callee_abis;
> + rtx_insn *insn;
> + FOR_BB_INSNS (bb, insn)
> + if (CALL_P (insn))
> + callee_abis.note_callee_abi (insn_callee_abi (insn));
> + HARD_REG_SET extra_caller_saves = callee_abis.caller_save_regs
> (*crtl->abi);
> +
> + /* GPRs are used in a bb if they are in the IN, GEN, or KILL sets. */
> + for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
> + if (!fixed_regs[regno]
> + && (TEST_HARD_REG_BIT (extra_caller_saves, regno)
> + || bitmap_bit_p (in, regno)
> + || bitmap_bit_p (gen, regno)
> + || bitmap_bit_p (kill, regno)))
> + bitmap_set_bit (components, regno);
> +
> + return components;
> +}
> +
> +/* Implement TARGET_SHRINK_WRAP_DISQUALIFY_COMPONENTS. */
> +void
> +ix86_disqualify_components (sbitmap, edge, sbitmap, bool)
> +{
> + /* Nothing to do for i386. */
> +}
> +
> +/* Implement TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS. */
> +void
> +ix86_emit_prologue_components (sbitmap components)
> +{
> + HOST_WIDE_INT cfa_offset;
> + struct machine_function *m = cfun->machine;
> +
> + cfa_offset = m->frame.reg_save_offset + m->fs.sp_offset
> + - m->frame.stack_pointer_offset;
> + for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
> + if (GENERAL_REGNO_P (regno) && ix86_save_reg (regno, true, true))
> + {
> + if (bitmap_bit_p (components, regno))
> + ix86_emit_save_reg_using_mov (word_mode, regno, cfa_offset);
> + cfa_offset -= UNITS_PER_WORD;
> + }
> +}
> +
> +/* Implement TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS. */
> +void
> +ix86_emit_epilogue_components (sbitmap components)
> +{
> + HOST_WIDE_INT cfa_offset;
> + struct machine_function *m = cfun->machine;
> + cfa_offset = m->frame.reg_save_offset + m->fs.sp_offset
> + - m->frame.stack_pointer_offset;
> +
> + for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
> + if (GENERAL_REGNO_P (regno) && ix86_save_reg (regno, true, true))
> + {
> + if (bitmap_bit_p (components, regno))
> + {
> + rtx reg = gen_rtx_REG (word_mode, regno);
> + rtx mem;
> + rtx_insn *insn;
> +
> + mem = choose_baseaddr (cfa_offset, NULL);
> + mem = gen_frame_mem (word_mode, mem);
> + insn = emit_move_insn (reg, mem);
> +
> + RTX_FRAME_RELATED_P (insn) = 1;
> + add_reg_note (insn, REG_CFA_RESTORE, reg);
> + }
> + cfa_offset -= UNITS_PER_WORD;
> + }
> +}
> +
> +void
> +ix86_set_handled_components (sbitmap components)
> +{
> + for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
> + if (bitmap_bit_p (components, regno))
> + {
> + cfun->machine->reg_is_wrapped_separately[regno] = true;
> + cfun->machine->use_fast_prologue_epilogue = true;
> + cfun->machine->frame.save_regs_using_mov = true;
> + }
> +}
> +
> +#undef TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS
> +#define TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS
> ix86_get_separate_components
> +#undef TARGET_SHRINK_WRAP_COMPONENTS_FOR_BB
> +#define TARGET_SHRINK_WRAP_COMPONENTS_FOR_BB ix86_components_for_bb
> +#undef TARGET_SHRINK_WRAP_DISQUALIFY_COMPONENTS
> +#define TARGET_SHRINK_WRAP_DISQUALIFY_COMPONENTS ix86_disqualify_components
> +#undef TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS
> +#define TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS \
> + ix86_emit_prologue_components
> +#undef TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS
> +#define TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS \
> + ix86_emit_epilogue_components
> +#undef TARGET_SHRINK_WRAP_SET_HANDLED_COMPONENTS
> +#define TARGET_SHRINK_WRAP_SET_HANDLED_COMPONENTS ix86_set_handled_components
> +
> struct gcc_target targetm = TARGET_INITIALIZER;
>
> #include "gt-i386.h"
> diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
> index 18fa97a9eb0..e89e57f8278 100644
> --- a/gcc/config/i386/i386.h
> +++ b/gcc/config/i386/i386.h
> @@ -2817,6 +2817,7 @@ struct GTY(()) machine_function {
> /* Cached initial frame layout for the current function. */
> struct ix86_frame frame;
>
> + bool reg_is_wrapped_separately[FIRST_PSEUDO_REGISTER];
> /* For -fsplit-stack support: A stack local which holds a pointer to
> the stack arguments for a function with a variable number of
> arguments. This is set at the start of the function and is used
> diff --git a/gcc/testsuite/g++.target/i386/shrink_wrap_separate.c
> b/gcc/testsuite/g++.target/i386/shrink_wrap_separate.c
> new file mode 100644
> index 00000000000..8be04822ac3
> --- /dev/null
> +++ b/gcc/testsuite/g++.target/i386/shrink_wrap_separate.c
> @@ -0,0 +1,24 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-rtl-pro_and_epilogue" } */
> +typedef struct a b;
> +typedef double c;
> +struct a {
> + b *d;
> + b *e;
> +};
> +struct f {
> + c g;
> +};
> +inline bool h(c i, b *m) {
> + b *j = m->e;
> + for (; m->e; j = j->d)
> + if (h(i, j))
> + return 0;
> + return m;
> +}
> +bool k() {
> + f *l;
> + b *n;
> + h(l->g, n);
> +}
> +/* { dg-final { scan-rtl-dump "The components we wrap separately are \[sep
> 40 41 42 43\]" "pro_and_epilogue" } } */
> diff --git a/gcc/testsuite/gcc.target/i386/interrupt-16.c
> b/gcc/testsuite/gcc.target/i386/interrupt-16.c
> index cb45ba54e3d..ca4441b3aee 100644
> --- a/gcc/testsuite/gcc.target/i386/interrupt-16.c
> +++ b/gcc/testsuite/gcc.target/i386/interrupt-16.c
> @@ -18,5 +18,5 @@ foo (int i)
> /* { dg-final { scan-assembler-not "(push|pop)(l|q)\[\\t \]*%(r|e)bp" } } */
> /* { dg-final { scan-assembler-not "(push|pop)l\[\\t \]*%edi" { target ia32
> } } } */
> /* { dg-final { scan-assembler-not "(push|pop)q\[\\t \]*%r\[0-9\]+" { target
> { ! ia32 } } } } */
> -/* { dg-final { scan-assembler-times "pushq\[\\t \]*%rdi" 1 { target { !
> ia32 } } } } */
> -/* { dg-final { scan-assembler-times "popq\[\\t \]*%rdi" 1 { target { ! ia32
> } } } } */
> +/* { dg-final { scan-assembler-times "(pushq.*%rdi|subq.*\\\$8,.*%rsp)" 1 {
> target { ! ia32 } } } } */
> +/* { dg-final { scan-assembler-times "(popq.*%rdi|addq.*\\\$8,.*%rsp)" 1 {
> target { ! ia32 } } } } */
> diff --git a/gcc/testsuite/gcc.target/x86_64/abi/callabi/leaf-2.c
> b/gcc/testsuite/gcc.target/x86_64/abi/callabi/leaf-2.c
> index 5f3d3e166af..46fc4648dbd 100644
> --- a/gcc/testsuite/gcc.target/x86_64/abi/callabi/leaf-2.c
> +++ b/gcc/testsuite/gcc.target/x86_64/abi/callabi/leaf-2.c
> @@ -1,5 +1,5 @@
> /* { dg-do compile } */
> -/* { dg-options "-O2 -fno-tree-vectorize -mabi=sysv" } */
> +/* { dg-options "-O2 -fno-tree-vectorize -mabi=sysv
> -fno-shrink-wrap-separate" } */
>
> extern int glb1, gbl2, gbl3;
>
> --
> 2.34.1
>
