http://llvm.org/bugs/show_bug.cgi?id=10853
Summary: [AVX,perf?] suboptimal code generated to set 'all bits
on' in ymm register
Product: new-bugs
Version: trunk
Platform: PC
OS/Version: All
Status: NEW
Severity: normal
Priority: P
Component: new bugs
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Given:
define <8 x i32> @foo() {
ret <8 x i32> <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32
-1>
}
The AVX backend generates the code:
_foo: ## @foo
vpcmpeqd %xmm0, %xmm0, %xmm0
vinsertf128 $1, %xmm0, %ymm0, %ymm0
ret
Unless I'm missing something, I think this could be more efficiently done with
something like:
vcmpeqd %ymm0, %ymm0, %ymm0
(There may be an AVX subtlety that I'm not aware of that prevents this;
apologies if so!)
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