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the same say the "test" instruction does in overflow cases, so eliminating the test is only safe when those bits aren't needed, as is the case for COND_E and COND_NE, or if it can be proven that no overflow will occur. For now, just restrict the optimization to COND_E and COND_NE and don't do any overflow analysis. llvm-svn: 66318
18 lines
667 B
LLVM
18 lines
667 B
LLVM
; RUN: llvm-as < %s | llc -march=x86 | grep testl
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; It's tempting to eliminate the testl instruction here and just use the
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; EFLAGS value from the incl, however it can't be known whether the add
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; will overflow, and if it does the incl would set OF, and the
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; subsequent setg would return true.
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target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
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target triple = "i386-apple-darwin9.6"
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define i32 @f(i32 %j) nounwind readnone {
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entry:
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%0 = add i32 %j, 1 ; <i32> [#uses=1]
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%1 = icmp sgt i32 %0, 0 ; <i1> [#uses=1]
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%2 = zext i1 %1 to i32 ; <i32> [#uses=1]
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ret i32 %2
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}
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