https://llvm.org/bugs/show_bug.cgi?id=31287
Bug ID: 31287
Summary: x86 backend should prefer pinsrw over movzwl + movd?
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: efrie...@codeaurora.org
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Take a testcase like the following:
define <16 x i8> @f(<2 x i8> *%p) {
%t = load <2 x i8>, <2 x i8> *%p
%r = shufflevector <2 x i8> %t, <2 x i8> undef, <16 x i32> <i32 0, i32 1, i32
2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2, i32 2,
i32 2, i32 2>
ret <16 x i8> %r
}
Using "llc -mtriple=x86_64-pc-linux-gnu -mattr=+avx", we generate:
movzwl (%rdi), %eax
vmovd %eax, %xmm0
retq
Potential alternate sequence, which I expect is a little faster (not tested):
vpxor %xmm0, %xmm0, %xmm0
vpinsrw $0, (%rdi), %xmm0, %xmm0
retq
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