https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106081
Bug ID: 106081
Summary: missed vectorization
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: hubicka at gcc dot gnu.org
Target Milestone: ---
This testcase (derived from ImageMagick)
struct pixels
{
short a,b,c,d;
} *pixels;
struct dpixels
{
double a,b,c,d;
};
double
test(double *k)
{
struct dpixels results={};
for (int u=0; u<10000;u++,k--)
{
results.a += *k*pixels[u].a;
results.b += *k*pixels[u].b;
results.c += *k*pixels[u].c;
results.d += *k*pixels[u].d;
}
return results.a+results.b*2+results.c*3+results.d*4;
}
gets vectorized by clang:
test: # @test
.cfi_startproc
# %bb.0:
movq pixels(%rip), %rax
vxorpd %xmm0, %xmm0, %xmm0
xorl %ecx, %ecx
.p2align 4, 0x90
.LBB0_1: # =>This Inner Loop Header: Depth=1
vpmovsxwd (%rax), %xmm1
vbroadcastsd (%rdi,%rcx,8), %ymm2
addq $8, %rax
decq %rcx
vcvtdq2pd %xmm1, %ymm1
vfmadd231pd %ymm2, %ymm1, %ymm0 # ymm0 = (ymm1 * ymm2) + ymm0
cmpq $-10000, %rcx # imm = 0xD8F0
jne .LBB0_1
# %bb.2:
vpermilpd $1, %xmm0, %xmm1 # xmm1 = xmm0[1,0]
vfmadd132sd .LCPI0_0(%rip), %xmm0, %xmm1 # xmm1 = (xmm1 * mem) +
xmm0
vextractf128 $1, %ymm0, %xmm0
vfmadd231sd .LCPI0_1(%rip), %xmm0, %xmm1 # xmm1 = (xmm0 * mem) +
xmm1
vpermilpd $1, %xmm0, %xmm0 # xmm0 = xmm0[1,0]
vfmadd132sd .LCPI0_2(%rip), %xmm1, %xmm0 # xmm0 = (xmm0 * mem) +
xmm1
vzeroupper
retq
but not by GCC.
Original loop is:
0.94 : 423cb0: vmovdqu (%rsi,%rdi,8),%xmm5 // morphology.c:2984
: 2983 if ( IsNaN(*k) ) continue;
0.29 : 423cb5: vpermilpd $0x1,(%rcx),%xmm4
: 2982 for (u=0; u < (ssize_t) kernel->width; u++, k--) {
0.46 : 423cbb: add $0x2,%rdi
0.07 : 423cbf: add $0xfffffffffffffff0,%rcx
: 2984 result.red += (*k)*k_pixels[u].red;
0.03 : 423cc3: vpshufb %xmm12,%xmm5,%xmm6
6.81 : 423cc8: vcvtdq2pd %xmm6,%xmm6
13.05 : 423ccc: vfmadd231pd %xmm6,%xmm4,%xmm1
: 2985 result.green += (*k)*k_pixels[u].green;
17.45 : 423cd1: vpshufb %xmm15,%xmm5,%xmm6 // morphology.c:2985
0.33 : 423cd6: vcvtdq2pd %xmm6,%xmm6
0.00 : 423cda: vfmadd231pd %xmm6,%xmm4,%xmm3
: 2986 result.blue += (*k)*k_pixels[u].blue;
15.28 : 423cdf: vpshufb %xmm13,%xmm5,%xmm6 // morphology.c:2986
: 2987 result.opacity += (*k)*k_pixels[u].opacity;
0.00 : 423ce4: vpshufb %xmm8,%xmm5,%xmm5
: 2986 result.blue += (*k)*k_pixels[u].blue;
0.00 : 423ce9: vcvtdq2pd %xmm6,%xmm6
: 2987 result.opacity += (*k)*k_pixels[u].opacity;
0.21 : 423ced: vcvtdq2pd %xmm5,%xmm5
: 2986 result.blue += (*k)*k_pixels[u].blue;
0.97 : 423cf1: vfmadd231pd %xmm6,%xmm4,%xmm0
: 2987 result.opacity += (*k)*k_pixels[u].opacity;
19.16 : 423cf6: vfmadd231pd %xmm5,%xmm4,%xmm2 // morphology.c:2987
: 2982 for (u=0; u < (ssize_t) kernel->width; u++, k--) {
14.51 : 423cfb: cmp %rdi,%rbp // morphology.c:2982
0.00 : 423cfe: jne 423cb0 <MorphologyApply.6136+0x20c0>
Changing short to double makes it vectorized:
.L2:
vmovupd (%rax), %ymm4
vmovupd 64(%rax), %ymm2
subq $-128, %rax
subq $32, %rdx
vunpcklpd -96(%rax), %ymm4, %ymm1
vunpckhpd -96(%rax), %ymm4, %ymm0
vmovupd -64(%rax), %ymm4
vunpckhpd -32(%rax), %ymm2, %ymm2
vunpcklpd -32(%rax), %ymm4, %ymm4
vpermpd $27, 32(%rdx), %ymm3
vpermpd $216, %ymm1, %ymm1
vpermpd $216, %ymm0, %ymm0
vpermpd $216, %ymm2, %ymm2
vpermpd $216, %ymm4, %ymm4
vunpcklpd %ymm2, %ymm0, %ymm10
vunpckhpd %ymm2, %ymm0, %ymm0
vunpckhpd %ymm4, %ymm1, %ymm9
vunpcklpd %ymm4, %ymm1, %ymm1
vpermpd $216, %ymm10, %ymm10
vpermpd $216, %ymm0, %ymm0
vfmadd231pd %ymm3, %ymm10, %ymm6
vfmadd231pd %ymm3, %ymm0, %ymm8
vpermpd $216, %ymm9, %ymm9
vpermpd $216, %ymm1, %ymm1
vfmadd231pd %ymm3, %ymm1, %ymm5
vfmadd231pd %ymm3, %ymm9, %ymm7
cmpq %rax, %rcx
jne .L2
howver clang's code looks shorter:
LBB0_1: # =>This Inner Loop Header: Depth=1
vbroadcastsd (%rdi,%rcx,8), %ymm1
vfmadd231pd (%rax), %ymm1, %ymm0 # ymm0 = (ymm1 * mem) + ymm0
addq $32, %rax
decq %rcx
cmpq $-10000, %rcx # imm = 0xD8F0
jne .LBB0_1
We loop vectorize while clang slp vectorizes it seems.
