https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112105
Bug ID: 112105
Summary: [14 Regression] vector by lane operation costing
broken since
g:21416caf221fae4351319ef8ca8d41c0234bdfa7
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: tnfchris at gcc dot gnu.org
CC: rsandifo at gcc dot gnu.org
Target Milestone: ---
Target: aarch64-*
After this commit g:21416caf221fae4351319ef8ca8d41c0234bdfa7
commit 21416caf221fae4351319ef8ca8d41c0234bdfa7
Author: Richard Sandiford <[email protected]>
Date: Tue Oct 24 11:01:52 2023 +0100
aarch64: Define TARGET_INSN_COST
This patch adds a bare-bones TARGET_INSN_COST. See the comment
in the patch for the rationale.
we now fail to form by lane instructions when they're not single use:
> cat test.c
#include <arm_neon.h>
typedef struct {
float re;
float im;
} cmplx_f32_t;
void test2x2_f32(const cmplx_f32_t *p_src_a,
const cmplx_f32_t *p_src_b,
cmplx_f32_t *p_dst) {
const float32_t *a_ptr = (const float32_t *)p_src_a;
const float32_t *b_ptr = (const float32_t *)p_src_b;
float32_t *out_ptr = (float32_t *)p_dst;
float32x2x2_t a_col[2];
float32x2x2_t b[2];
float32x2x2_t result[2];
a_col[0] = vld2_f32(a_ptr);
b[0] = vld2_f32(b_ptr);
result[0].val[0] = vmul_lane_f32(a_col[0].val[0], b[0].val[0], 0);
result[0].val[1] = vmul_lane_f32(a_col[0].val[1], b[0].val[0], 0);
vst2_f32(out_ptr, result[0]);
out_ptr = out_ptr + 4;
}
---
> ./bin/gcc test.c -O1 -S -o -
...
test2x2_f32:
ld2 {v27.2s - v28.2s}, [x0]
ld2 {v30.2s - v31.2s}, [x1]
dup v31.2s, v30.s[0]
fmul v29.2s, v31.2s, v27.2s
fmul v30.2s, v31.2s, v28.2s
st2 {v29.2s - v30.2s}, [x2]
ret
which has an unneeded dup. Before this we generated:
test2x2_f32:
ld2 {v0.2s - v1.2s}, [x1]
ld2 {v4.2s - v5.2s}, [x0]
fmul v2.2s, v4.2s, v0.s[0]
fmul v3.2s, v5.2s, v0.s[0]
st2 {v2.2s - v3.2s}, [x2]
ret
