https://bugs.llvm.org/show_bug.cgi?id=48046
Bug ID: 48046
Summary: Better codegen for strided load
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected],
[email protected]
#define N 4
float x[4*N], y[N];
void foo (int p)
{
int i;
for (i = 0; i < N; i++)
y[i] = x[p + 3*i];
}
Clang -O3 -mavx2:
foo(int): # @foo(int)
movsxd rax, edi
vmovss xmm0, dword ptr [4*rax + x] # xmm0 = mem[0],zero,zero,zero
vmovss dword ptr [rip + y], xmm0
vmovss xmm0, dword ptr [4*rax + x+12] # xmm0 = mem[0],zero,zero,zero
vmovss dword ptr [rip + y+4], xmm0
vmovss xmm0, dword ptr [4*rax + x+24] # xmm0 = mem[0],zero,zero,zero
vmovss dword ptr [rip + y+8], xmm0
vmovss xmm0, dword ptr [4*rax + x+36] # xmm0 = mem[0],zero,zero,zero
vmovss dword ptr [rip + y+12], xmm0
ret
ICC -O3 -mavx2:
foo(int):
movsxd rdi, edi #6.1
vmovss xmm16, DWORD PTR [12+x+rdi*4] #10.12
vmovss xmm17, DWORD PTR [x+rdi*4] #10.12
vinsertps xmm1, xmm16, DWORD PTR [36+x+rdi*4], 16 #10.12
vinsertps xmm0, xmm17, DWORD PTR [24+x+rdi*4], 16 #10.12
vunpcklps xmm2, xmm0, xmm1 #10.12
vmovups XMMWORD PTR y[rip], xmm2 #10.5
ret #11.1
x:
y:
GCC -O3 -mavx2:
foo(int):
movsx rdi, edi
vmovss xmm0, DWORD PTR x[0+rdi*4]
vinsertps xmm0, xmm0, DWORD PTR x[12+rdi*4], 0x10
vmovlps QWORD PTR y[rip], xmm0
vmovss xmm0, DWORD PTR x[24+rdi*4]
vinsertps xmm0, xmm0, DWORD PTR x[36+rdi*4], 0x10
vmovlps QWORD PTR y[rip+8], xmm0
ret
y:
GCC has the best Block RThroughput value - 2.5.
https://godbolt.org/z/Pc1TWz
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