DAG: Combine (and (setne X, 0), (setne X, -1)) -> (setuge (add X, 1), 2)
A common idiom is to use zero and all-ones as sentinal values and to
check for both in a single conditional ("x != 0 && x != (unsigned)-1").
That generates code, for i32, like:
testl %edi, %edi
setne %al
cmpl $-1, %edi
setne %cl
andb %al, %cl
With this transform, we generate the simpler:
incl %edi
cmpl $1, %edi
seta %al
Similar improvements for other integer sizes and on other platforms. In
general, combining the two setcc instructions into one is better.
rdar://14689217
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188315 91177308-0d34-0410-b5e6-96231b3b80d8
2013-08-13 21:30:58 +00:00
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; RUN: llc < %s -mcpu=generic -march=x86-64 -asm-verbose=false | FileCheck %s
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define zeroext i1 @test0(i64 %x) nounwind {
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; CHECK-LABEL: test0:
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2013-08-14 00:46:00 +00:00
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; CHECK-NEXT: incq %[[X:rdi|rcx]]
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; CHECK-NEXT: cmpq $1, %[[X]]
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DAG: Combine (and (setne X, 0), (setne X, -1)) -> (setuge (add X, 1), 2)
A common idiom is to use zero and all-ones as sentinal values and to
check for both in a single conditional ("x != 0 && x != (unsigned)-1").
That generates code, for i32, like:
testl %edi, %edi
setne %al
cmpl $-1, %edi
setne %cl
andb %al, %cl
With this transform, we generate the simpler:
incl %edi
cmpl $1, %edi
seta %al
Similar improvements for other integer sizes and on other platforms. In
general, combining the two setcc instructions into one is better.
rdar://14689217
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188315 91177308-0d34-0410-b5e6-96231b3b80d8
2013-08-13 21:30:58 +00:00
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; CHECK-NEXT: seta %al
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; CHECK-NEXT: ret
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%cmp1 = icmp ne i64 %x, -1
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%not.cmp = icmp ne i64 %x, 0
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%.cmp1 = and i1 %cmp1, %not.cmp
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ret i1 %.cmp1
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}
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