On Fri, Aug 1, 2025 at 8:10 PM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> Don't hoist non all 0s/1s vector set outside of the loop to avoid extra
> spills.
The patch LGTM.
>
> gcc/
>
> PR target/120941
> * config/i386/i386-features.cc (x86_cse_kind): Moved before
> ix86_place_single_vector_set.
> (redundant_load): Likewise.
> (ix86_place_single_vector_set): Replace the last argument to the
> pointer to redundant_load. For X86_CSE_VEC_DUP, don't place the
> vector set outside of the loop to avoid extra spills.
> (remove_redundant_vector_load): Pass load to
> ix86_place_single_vector_set.
>
> gcc/testsuite/
>
> PR target/120941
> * gcc.target/i386/pr120941-1.c: New test.
>
> Signed-off-by: H.J. Lu <hjl.to...@gmail.com>
> ---
> gcc/config/i386/i386-features.cc | 107 +++++++++++----------
> gcc/testsuite/gcc.target/i386/pr120941-1.c | 49 ++++++++++
> 2 files changed, 106 insertions(+), 50 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/pr120941-1.c
>
> diff --git a/gcc/config/i386/i386-features.cc
> b/gcc/config/i386/i386-features.cc
> index 53e86c8a493..9941e61361c 100644
> --- a/gcc/config/i386/i386-features.cc
> +++ b/gcc/config/i386/i386-features.cc
> @@ -3085,21 +3085,63 @@ ix86_rpad_gate ()
> && optimize_function_for_speed_p (cfun));
> }
>
> +enum x86_cse_kind
> +{
> + X86_CSE_CONST0_VECTOR,
> + X86_CSE_CONSTM1_VECTOR,
> + X86_CSE_VEC_DUP
> +};
> +
> +struct redundant_load
> +{
> + /* Bitmap of basic blocks with broadcast instructions. */
> + auto_bitmap bbs;
> + /* Bitmap of broadcast instructions. */
> + auto_bitmap insns;
> + /* The broadcast inner scalar. */
> + rtx val;
> + /* The inner scalar mode. */
> + machine_mode mode;
> + /* The instruction which sets the inner scalar. Nullptr if the inner
> + scalar is applied to the whole function, instead of within the same
> + block. */
> + rtx_insn *def_insn;
> + /* The widest broadcast source. */
> + rtx broadcast_source;
> + /* The widest broadcast register. */
> + rtx broadcast_reg;
> + /* The basic block of the broadcast instruction. */
> + basic_block bb;
> + /* The number of broadcast instructions with the same inner scalar. */
> + unsigned HOST_WIDE_INT count;
> + /* The threshold of broadcast instructions with the same inner
> + scalar. */
> + unsigned int threshold;
> + /* The widest broadcast size in bytes. */
> + unsigned int size;
> + /* Load kind. */
> + x86_cse_kind kind;
> +};
> +
> /* Generate a vector set, DEST = SRC, at entry of the nearest dominator
> for basic block map BBS, which is in the fake loop that contains the
> whole function, so that there is only a single vector set in the
> - whole function. If not nullptr, INNER_SCALAR is the inner scalar of
> - SRC, as (reg:SI 99) in (vec_duplicate:V4SI (reg:SI 99)). */
> + whole function. If not nullptr, LOAD is a pointer to the load. */
>
> static void
> ix86_place_single_vector_set (rtx dest, rtx src, bitmap bbs,
> - rtx inner_scalar = nullptr)
> + redundant_load *load = nullptr)
> {
> basic_block bb = nearest_common_dominator_for_set (CDI_DOMINATORS, bbs);
> - while (bb->loop_father->latch
> - != EXIT_BLOCK_PTR_FOR_FN (cfun))
> - bb = get_immediate_dominator (CDI_DOMINATORS,
> - bb->loop_father->header);
> + /* For X86_CSE_VEC_DUP, don't place the vector set outside of the loop
> + to avoid extra spills. */
> + if (!load || load->kind != X86_CSE_VEC_DUP)
> + {
> + while (bb->loop_father->latch
> + != EXIT_BLOCK_PTR_FOR_FN (cfun))
> + bb = get_immediate_dominator (CDI_DOMINATORS,
> + bb->loop_father->header);
> + }
>
> rtx set = gen_rtx_SET (dest, src);
>
> @@ -3141,8 +3183,14 @@ ix86_place_single_vector_set (rtx dest, rtx src,
> bitmap bbs,
> }
> }
>
> - if (inner_scalar)
> + if (load && load->kind == X86_CSE_VEC_DUP)
> {
> + /* Get the source from LOAD as (reg:SI 99) in
> +
> + (vec_duplicate:V4SI (reg:SI 99))
> +
> + */
> + rtx inner_scalar = load->val;
> /* Set the source in (vec_duplicate:V4SI (reg:SI 99)). */
> rtx reg = XEXP (src, 0);
> if ((REG_P (inner_scalar) || MEM_P (inner_scalar))
> @@ -3489,44 +3537,6 @@ replace_vector_const (machine_mode vector_mode, rtx
> vector_const,
> }
> }
>
> -enum x86_cse_kind
> -{
> - X86_CSE_CONST0_VECTOR,
> - X86_CSE_CONSTM1_VECTOR,
> - X86_CSE_VEC_DUP
> -};
> -
> -struct redundant_load
> -{
> - /* Bitmap of basic blocks with broadcast instructions. */
> - auto_bitmap bbs;
> - /* Bitmap of broadcast instructions. */
> - auto_bitmap insns;
> - /* The broadcast inner scalar. */
> - rtx val;
> - /* The inner scalar mode. */
> - machine_mode mode;
> - /* The instruction which sets the inner scalar. Nullptr if the inner
> - scalar is applied to the whole function, instead of within the same
> - block. */
> - rtx_insn *def_insn;
> - /* The widest broadcast source. */
> - rtx broadcast_source;
> - /* The widest broadcast register. */
> - rtx broadcast_reg;
> - /* The basic block of the broadcast instruction. */
> - basic_block bb;
> - /* The number of broadcast instructions with the same inner scalar. */
> - unsigned HOST_WIDE_INT count;
> - /* The threshold of broadcast instructions with the same inner
> - scalar. */
> - unsigned int threshold;
> - /* The widest broadcast size in bytes. */
> - unsigned int size;
> - /* Load kind. */
> - x86_cse_kind kind;
> -};
> -
> /* Return the inner scalar if OP is a broadcast, else return nullptr. */
>
> static rtx
> @@ -3872,10 +3882,7 @@ remove_redundant_vector_load (void)
> else
> ix86_place_single_vector_set (load->broadcast_reg,
> load->broadcast_source,
> - load->bbs,
> - (load->kind == X86_CSE_VEC_DUP
> - ? load->val
> - : nullptr));
> + load->bbs, load);
> }
>
> loop_optimizer_finalize ();
> diff --git a/gcc/testsuite/gcc.target/i386/pr120941-1.c
> b/gcc/testsuite/gcc.target/i386/pr120941-1.c
> new file mode 100644
> index 00000000000..b4fc6ac97fc
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr120941-1.c
> @@ -0,0 +1,49 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Ofast -march=x86-64-v3" } */
> +/* Keep labels and directives ('.cfi_startproc', '.cfi_endproc'). */
> +/* { dg-final { check-function-bodies "**" "" "" { target lp64 } {^\t?\.} }
> } */
> +
> +/*
> +**bar:
> +**.LFB[0-9]+:
> +**...
> +** vbroadcastsd .LC4\(%rip\), %ymm2
> +** leal 2\(%rbx\), %eax
> +** vbroadcastsd .LC2\(%rip\), %ymm4
> +** negl %eax
> +**...
> +*/
> +
> +extern void foo (int);
> +
> +enum { N_CELL_ENTRIES1 = 2 }
> +typedef LBM_Grid1[64];
> +enum { N_CELL_ENTRIES2 = 2 }
> +typedef LBM_Grid2[64];
> +LBM_Grid1 grid1;
> +LBM_Grid2 grid2;
> +extern int n;
> +
> +void
> +LBM_handleInOutFlow()
> +{
> + int i, j;
> + for (; i; i += 2)
> + {
> + for (j = 0; j < n; j++)
> + {
> + grid1[i] = 1.0 / 36.0 * i;
> + grid2[i] = 1.0 / 36.0 * i;
> + }
> + }
> +}
> +
> +int main_t;
> +void
> +bar (void)
> +{
> + for (; main_t; main_t++) {
> + LBM_handleInOutFlow();
> + foo (main_t);
> + }
> +}
> --
> 2.50.1
>
--
BR,
Hongtao
