https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99407
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2021-03-08
Ever confirmed|0 |1
Keywords| |missed-optimization
Blocks| |53947
Summary|s243 benchmark of TSVC is |s243 benchmark of TSVC is
|vectorized by clang and not |vectorized by clang and not
|by gcc |by gcc, missed DSE
Component|middle-end |tree-optimization
Status|UNCONFIRMED |NEW
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, wonder why DSE didn't remove the first a[i] store. Ah, because DSE
doesn't use data-ref analysis and thus cannot disambiguate the variable offset.
Manually applying DSE produces
.L4:
vmovaps c(%rax), %ymm1
vaddps e(%rax), %ymm1, %ymm0
addq $32, %rax
vmovups a-28(%rax), %ymm1
vmulps d-32(%rax), %ymm1, %ymm1
vmulps d-32(%rax), %ymm0, %ymm0
vaddps b-32(%rax), %ymm0, %ymm0
vmovaps %ymm0, b-32(%rax)
vaddps %ymm0, %ymm1, %ymm0
vmovaps %ymm0, a-32(%rax)
cmpq $127968, %rax
jne .L4
manually DSEd loop:
for (int nl = 0; nl < iterations; nl++) {
for (int i = 0; i < LEN_1D-1; i++) {
real_t tem = b[i] + c[i ] * d[i];
b[i] = tem + d[i ] * e[i];
a[i] = b[i] + a[i+1] * d[i];
}
}
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations
