https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110148
--- Comment #3 from cuilili <lili.cui at intel dot com> ---
I reproduced S1244 regression on znver3.
Src code:
for (int i = 0; i < LEN_1D-1; i++)
{
a[i] = b[i] + c[i] * c[i] + b[i] * b[i] + c[i];
d[i] = a[i] + a[i+1];
}
--------------------------------------------------------
Base version: Base + commit version:
Assembler Assembler
Loop1: Loop1:
vmovsd 0x60c400(%rax),%xmm2 vmovsd 0x60ba00(%rax),%xmm2
vmovsd 0x60ba00(%rax),%xmm1 vmovsd 0x60c400(%rax),%xmm1
add $0x8,%rax add $0x8,%rax
--------------------------------------------------------------------
vaddsd %xmm1,%xmm2,%xmm0 vmovsd %xmm2,%xmm2,%xmm0
vmulsd %xmm2,%xmm2,%xmm2 vfmadd132sd %xmm2,%xmm1,%xmm0
vfmadd132sd %xmm1,%xmm2,%xmm1 vfmadd132sd %xmm1,%xmm2,%xmm1
--------------------------------------------------------------------
vaddsd %xmm1,%xmm0,%xmm0 vaddsd %xmm1,%xmm0,%xmm0
vmovsd %xmm0,0x60cdf8(%rax) vmovsd %xmm0,0x60cdf8(%rax)
vaddsd 0x60ce00(%rax),%xmm0,%xmm0 vaddsd 0x60ce00(%rax),%xmm0,%xmm0
vmovsd %xmm0,0x60aff8(%rax) vmovsd %xmm0,0x60aff8(%rax)
cmp $0x9f8,%rax cmp $0x9f8,%rax
jne Loop1: jne Loop1
For the Base version, mult and FMA have dependencies, which increases the
latency of the critical dependency chain. I didn't find out why znver3 has
regression. Same binary running on ICX has 11% gain (with #define iterations
100000000).
