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i386: Add combiner splitter to optimize V2SImode memory rotation [PR96166]

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Since the x86 backend enabled V2SImode vectorization (with
TARGET_MMX_WITH_SSE), slp vectorization can kick in and emit
        movq    (%rdi), %xmm1
        pshufd  $225, %xmm1, %xmm0
        movq    %xmm0, (%rdi)
instead of
        rolq    $32, (%rdi)
we used to emit (or emit when slp vectorization is disabled).
I think the rotate is both smaller and faster, so this patch adds
a combiner splitter to optimize that back.

2021-02-13  Jakub Jelinek  <jakub@redhat.com>

	PR target/96166
	* config/i386/mmx.md (*mmx_pshufd_1): Add a combine splitter for
	swap of V2SImode elements in memory into DImode memory rotate by 32.

	* gcc.target/i386/pr96166.c: New test.
This commit is contained in:
Jakub Jelinek 2021-02-13 10:32:16 +01:00
parent fab095dad5
commit 0f3a743b68
2 changed files with 32 additions and 0 deletions
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11
gcc/config/i386/mmx.md
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@ -2076,6 +2076,17 @@
(set_attr "length_immediate" "1")
(set_attr "mode" "TI")])
;; Optimize V2SImode load from memory, swapping the elements and
;; storing back into the memory into DImode rotate of the memory by 32.
(define_split
[(set (match_operand:V2SI 0 "memory_operand")
(vec_select:V2SI (match_dup 0)
(parallel [(const_int 1) (const_int 0)])))]
"TARGET_64BIT && (TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ())"
[(set (match_dup 0)
(rotate:DI (match_dup 0) (const_int 32)))]
"operands[0] = adjust_address (operands[0], DImode, 0);")
(define_insn "mmx_pswapdv2si2"
[(set (match_operand:V2SI 0 "register_operand" "=y,Yv")
(vec_select:V2SI

21
gcc/testsuite/gcc.target/i386/pr96166.c Normal file
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@ -0,0 +1,21 @@
/* PR target/96166 */
/* { dg-do compile { target { ! ia32 } } } */
/* { dg-options "-O3 -mtune=generic -masm=att" } */
/* { dg-final { scan-assembler "rolq\\s\\\$32, \\\(%\[re]di\\\)" } } */
static inline void
swap (int *x, int *y)
{
int tmp = *x;
*x = *y;
*y = tmp;
}
void
bar (int (*x)[2])
{
int y[2];
__builtin_memcpy (&y, x, sizeof *x);
swap (&y[0], &y[1]);
__builtin_memcpy (x, &y, sizeof *x);
}