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When GVN wants to re-interpret an already available value in a smaller type, it needs to right-shift the value on big-endian systems to ensure the correct bytes are accessed. The shift value is the difference of the sizes of the two types. This is correct as long as both types occupy multiples of full bytes. However, when one of them is a sub-byte type like i1, this no longer holds true: we still need to shift, but only to access the correct *byte*. Accessing bits within the byte requires no shift in either endianness; e.g. an i1 resides in the least-significant bit of its containing byte on both big- and little-endian systems. Therefore, the appropriate shift value to be used is the difference of the *storage* sizes of the two types. This is already handled correctly in one place where such a shift takes place (GetStoreValueForLoad), but is incorrect in two other places: GetLoadValueForLoad and CoerceAvailableValueToLoadType. This patch changes both places to use the storage size as well. Differential Revision: http://reviews.llvm.org/D18662 llvm-svn: 265684
41 lines
1.8 KiB
LLVM
41 lines
1.8 KiB
LLVM
; RUN: opt -gvn -S < %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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;; Make sure we use correct bit shift based on storage size for
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;; loads reusing a load value.
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define i64 @test1({ i1, i8 }* %predA, { i1, i8 }* %predB) {
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; CHECK-LABEL: @test1
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; CHECK: [[V1:%.*]] = load i16, i16* %{{.*}}
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; CHECK: [[V2:%.*]] = lshr i16 [[V1]], 8
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; CHECK: trunc i16 [[V2]] to i1
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%valueLoadA.fca.0.gep = getelementptr inbounds { i1, i8 }, { i1, i8 }* %predA, i64 0, i32 0
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%valueLoadA.fca.0.load = load i1, i1* %valueLoadA.fca.0.gep, align 8
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%valueLoadB.fca.0.gep = getelementptr inbounds { i1, i8 }, { i1, i8 }* %predB, i64 0, i32 0
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%valueLoadB.fca.0.load = load i1, i1* %valueLoadB.fca.0.gep, align 8
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%isTrue = and i1 %valueLoadA.fca.0.load, %valueLoadB.fca.0.load
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%valueLoadA.fca.1.gep = getelementptr inbounds { i1, i8 }, { i1, i8 }* %predA, i64 0, i32 1
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%valueLoadA.fca.1.load = load i8, i8* %valueLoadA.fca.1.gep, align 1
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%isNotNullA = icmp ne i8 %valueLoadA.fca.1.load, 0
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%valueLoadB.fca.1.gep = getelementptr inbounds { i1, i8 }, { i1, i8 }* %predB, i64 0, i32 1
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%valueLoadB.fca.1.load = load i8, i8* %valueLoadB.fca.1.gep, align 1
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%isNotNullB = icmp ne i8 %valueLoadB.fca.1.load, 0
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%isNotNull = and i1 %isNotNullA, %isNotNullB
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%isTrueAndNotNull = and i1 %isTrue, %isNotNull
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%ret = zext i1 %isTrueAndNotNull to i64
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ret i64 %ret
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}
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;; And likewise for loads reusing a store value.
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define i1 @test2(i8 %V, i8* %P) {
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; CHECK-LABEL: @test2
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; CHECK-NOT: lshr
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store i8 %V, i8* %P
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%P2 = bitcast i8* %P to i1*
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%A = load i1, i1* %P2
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ret i1 %A
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}
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