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| author | Roger Sayle <roger@nextmovesoftware.com> | 2022-03-15 09:05:28 +0000 |
|---|---|---|
| committer | Roger Sayle <roger@nextmovesoftware.com> | 2022-03-15 09:05:28 +0000 |
| commit | 49fb0af9bf8f16907980d383c2bbc85e185ec2e0 (patch) | |
| tree | 2c78a41302d114f6aaf1defa3f7a64619c0dfe0d | |
| parent | efd1582926f3278a5e57ebab7d87fc870f06ecea (diff) | |
| download | gcc-49fb0af9bf8f16907980d383c2bbc85e185ec2e0.zip gcc-49fb0af9bf8f16907980d383c2bbc85e185ec2e0.tar.gz gcc-49fb0af9bf8f16907980d383c2bbc85e185ec2e0.tar.bz2 | |
PR tree-optimization/101895: Fold VEC_PERM to help recognize FMA.
This patch resolves PR tree-optimization/101895 a missed optimization
regression, by adding a costant folding simplification to match.pd to
simplify the transform "mult; vec_perm; plus" into "vec_perm; mult; plus"
with the aim that keeping the multiplication and addition next to each
other allows them to be recognized as fused-multiply-add on suitable
targets. This transformation requires a tweak to match.pd's
vec_same_elem_p predicate to handle CONSTRUCTOR_EXPRs using the same
SSA_NAME_DEF_STMT idiom used for constructors elsewhere in match.pd.
The net effect is that the following code example:
void foo(float * __restrict__ a, float b, float *c) {
a[0] = c[0]*b + a[0];
a[1] = c[2]*b + a[1];
a[2] = c[1]*b + a[2];
a[3] = c[3]*b + a[3];
}
when compiled on x86_64-pc-linux-gnu with -O2 -march=cascadelake
currently generates:
vbroadcastss %xmm0, %xmm0
vmulps (%rsi), %xmm0, %xmm0
vpermilps $216, %xmm0, %xmm0
vaddps (%rdi), %xmm0, %xmm0
vmovups %xmm0, (%rdi)
ret
but with this patch now generates the improved:
vpermilps $216, (%rsi), %xmm1
vbroadcastss %xmm0, %xmm0
vfmadd213ps (%rdi), %xmm0, %xmm1
vmovups %xmm1, (%rdi)
ret
2022-03-15 Roger Sayle <roger@nextmovesoftware.com>
Marc Glisse <marc.glisse@inria.fr>
Richard Biener <rguenther@suse.de>
gcc/ChangeLog
PR tree-optimization/101895
* match.pd (vec_same_elem_p): Handle CONSTRUCTOR_EXPR def.
(plus (vec_perm (mult ...) ...) ...): New reordering simplification.
gcc/testsuite/ChangeLog
PR tree-optimization/101895
* gcc.target/i386/pr101895.c: New test case.
| -rw-r--r-- | gcc/match.pd | 21 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.target/i386/pr101895.c | 11 |
2 files changed, 30 insertions, 2 deletions
diff --git a/gcc/match.pd b/gcc/match.pd index 8b44b5c..7d619f4 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -7692,16 +7692,33 @@ and, /* VEC_PERM_EXPR (v, v, mask) -> v where v contains same element. */ (match vec_same_elem_p + (vec_duplicate @0)) + +(match vec_same_elem_p + CONSTRUCTOR@0 + (if (TREE_CODE (@0) == SSA_NAME + && uniform_vector_p (gimple_assign_rhs1 (SSA_NAME_DEF_STMT (@0)))))) + +(match vec_same_elem_p @0 (if (uniform_vector_p (@0)))) -(match vec_same_elem_p - (vec_duplicate @0)) (simplify (vec_perm vec_same_elem_p@0 @0 @1) @0) +/* Push VEC_PERM earlier if that may help FMA perception (PR101895). */ +(simplify + (plus:c (vec_perm:s (mult:c@0 @1 vec_same_elem_p@2) @0 @3) @4) + (if (TREE_CODE (@0) == SSA_NAME && num_imm_uses (@0) == 2) + (plus (mult (vec_perm @1 @1 @3) @2) @4))) +(simplify + (minus (vec_perm:s (mult:c@0 @1 vec_same_elem_p@2) @0 @3) @4) + (if (TREE_CODE (@0) == SSA_NAME && num_imm_uses (@0) == 2) + (minus (mult (vec_perm @1 @1 @3) @2) @4))) + + /* Match count trailing zeroes for simplify_count_trailing_zeroes in fwprop. The canonical form is array[((x & -x) * C) >> SHIFT] where C is a magic constant which when multiplied by a power of 2 contains a unique value diff --git a/gcc/testsuite/gcc.target/i386/pr101895.c b/gcc/testsuite/gcc.target/i386/pr101895.c new file mode 100644 index 0000000..4d0f1cb --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr101895.c @@ -0,0 +1,11 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -march=cascadelake" } */ + +void foo(float * __restrict__ a, float b, float *c) { + a[0] = c[0]*b + a[0]; + a[1] = c[2]*b + a[1]; + a[2] = c[1]*b + a[2]; + a[3] = c[3]*b + a[3]; +} + +/* { dg-final { scan-assembler "vfmadd" } } */ |