https://bugs.llvm.org/show_bug.cgi?id=33483
Bug ID: 33483
Summary: [X86][SSE] Use re-materializable -1 for vector
increment/decrement
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: llvm-...@redking.me.uk
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
pe...@cordes.ca, spatel+l...@rotateright.com
define <4 x i32> @inc(<4 x i32>) {
%2 = add <4 x i32> %0, <i32 1, i32 1, i32 1, i32 1>
ret <4 x i32> %2
}
define <4 x i32> @dec(<4 x i32>) {
%2 = sub <4 x i32> %0, <i32 1, i32 1, i32 1, i32 1>
ret <4 x i32> %2
}
These currently do a constant load:
inc:
vpaddd .LCPI0_0(%rip), %xmm0, %xmm0
retq
dec:
vpsubd .LCPI1_0(%rip), %xmm0, %xmm0
retq
But they could do this using the re-materializable -1 value instead:
inc:
vcmpeqd %xmm1, %xmm1, %xmm1
vpsubd %xmm1, %xmm0, %xmm0
retq
dec:
vcmpeqd %xmm1, %xmm1, %xmm1
vpaddd %xmm1, %xmm0, %xmm0
retq
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