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As part of r251146 InstCombine was extended to call computeKnownBits on every value in the function to determine whether it happens to be constant. This increases typical compiletime by 1-3% (5% in irgen+opt time) in my measurements. On the other hand this case did not trigger once in the whole llvm-testsuite. This patch introduces the notion of ExpensiveCombines which are only enabled for OptLevel > 2. I removed the check in InstructionSimplify as that is called from various places where the OptLevel is not known but given the rarity of the situation I think a check in InstCombine is enough. Differential Revision: http://reviews.llvm.org/D16835 llvm-svn: 263047
46 lines
1.3 KiB
LLVM
46 lines
1.3 KiB
LLVM
; RUN: opt -S -instcombine -expensive-combines < %s | FileCheck %s
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target datalayout = "E-m:e-i64:64-n32:64"
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target triple = "powerpc64-unknown-linux-gnu"
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@d = global i32 15, align 4
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@b = global i32* @d, align 8
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@a = common global i32 0, align 4
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; Function Attrs: nounwind
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define signext i32 @main() #1 {
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entry:
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%0 = load i32*, i32** @b, align 8
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%1 = load i32, i32* @a, align 4
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%lnot = icmp eq i32 %1, 0
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%lnot.ext = zext i1 %lnot to i32
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%shr.i = lshr i32 2072, %lnot.ext
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%call.lobit = lshr i32 %shr.i, 7
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%2 = and i32 %call.lobit, 1
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%3 = load i32, i32* %0, align 4
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%or = or i32 %2, %3
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store i32 %or, i32* %0, align 4
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%4 = load i32, i32* @a, align 4
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%lnot.1 = icmp eq i32 %4, 0
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%lnot.ext.1 = zext i1 %lnot.1 to i32
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%shr.i.1 = lshr i32 2072, %lnot.ext.1
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%call.lobit.1 = lshr i32 %shr.i.1, 7
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%5 = and i32 %call.lobit.1, 1
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%or.1 = or i32 %5, %or
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store i32 %or.1, i32* %0, align 4
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ret i32 %or.1
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; Check that both InstCombine and InstSimplify can use computeKnownBits to
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; realize that:
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; ((2072 >> (L == 0)) >> 7) & 1
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; is always zero.
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; CHECK-LABEL: @main
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; CHECK: %[[V1:[0-9]+]] = load i32*, i32** @b, align 8
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; CHECK: %[[V2:[0-9]+]] = load i32, i32* %[[V1]], align 4
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; CHECK: ret i32 %[[V2]]
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}
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attributes #0 = { nounwind readnone }
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attributes #1 = { nounwind }
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