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83458d4d01
Original message: The attached is the fix to radar://11663049. The optimization can be outlined by following rules: (select (x != c), e, c) -> select (x != c), e, x), (select (x == c), c, e) -> select (x == c), x, e) where the <c> is an integer constant. The reason for this change is that : on x86, conditional-move-from-constant needs two instructions; however, conditional-move-from-register need only one instruction. While the LowerSELECT() sounds to be the most convenient place for this optimization, it turns out to be a bad place. The reason is that by replacing the constant <c> with a symbolic value, it obscure some instruction-combining opportunities which would otherwise be very easy to spot. For that reason, I have to postpone the change to last instruction-combining phase. The change passes the test of "make check-all -C <build-root/test" and "make -C project/test-suite/SingleSource". Original message since r165661: My previous change has a bug: I negated the condition code of a CMOV, and go ahead creating a new CMOV using the *ORIGINAL* condition code. llvm-svn: 166017
17 lines
347 B
LLVM
17 lines
347 B
LLVM
; RUN: llc < %s -mtriple=x86_64-apple-darwin10 -mcpu=corei7 | FileCheck %s
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define i64 @test1(i64 %x) nounwind {
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entry:
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%cmp = icmp eq i64 %x, 2
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%add = add i64 %x, 1
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%retval.0 = select i1 %cmp, i64 2, i64 %add
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ret i64 %retval.0
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; CHECK: test1:
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; CHECK: leaq 1(%rdi), %rax
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; CHECK: cmpq $2, %rdi
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; CHECK: cmoveq %rdi, %rax
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; CHECK: ret
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}
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