[Bug c++/105968] GCC vectorizes but reports that it did not vectorize
crazylht at gmail dot com
gcc-bugzilla@gcc.gnu.org
Tue Jun 14 09:02:19 GMT 2022
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105968
Hongtao.liu <crazylht at gmail dot com> changed:
What |Removed |Added
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CC| |crazylht at gmail dot com
--- Comment #1 from Hongtao.liu <crazylht at gmail dot com> ---
> even though vector instructions are generated.
>
No it's scalar instructions, but the issue here is why vectorizer is ok for -O2
-O2 -ftree-vectorize -mavx2 but not for -O3 -ftree-vectorize -mavx2
muladd():
xor eax, eax
.L2:
vmovsd xmm0, QWORD PTR a[rax]
vaddsd xmm0, xmm0, QWORD PTR b[rax]
add rax, 8
vmulsd xmm0, xmm0, QWORD PTR c[rax-8]
vmovsd QWORD PTR r[rax-8], xmm0
cmp rax, 80000
jne .L2
xor eax, eax
ret
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