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9cd4907159
Summary: We teach alias analysis that invariant.start is readonly. This helps with GVN and memcopy optimizations that currently treat. invariant.start as a clobber. We need to treat this as readonly, so that DSE does not incorrectly remove stores prior to the invariant.start Reviewers: sanjoy, reames, majnemer, dberlin Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D23214 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278138 91177308-0d34-0410-b5e6-96231b3b80d8
35 lines
1.2 KiB
LLVM
35 lines
1.2 KiB
LLVM
; Test to make sure llvm.invariant.start calls are not treated as clobbers.
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; RUN: opt < %s -basicaa -dse -S | FileCheck %s
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declare {}* @llvm.invariant.start.p0i8(i64, i8* nocapture) nounwind readonly
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; We cannot remove the store 1 to %p.
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; FIXME: By the semantics of invariant.start, the store 3 to p is unreachable.
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define void @test(i8 *%p) {
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store i8 1, i8* %p, align 4
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%i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %p)
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store i8 3, i8* %p, align 4
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ret void
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; CHECK-LABEL: @test(
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; CHECK-NEXT: store i8 1, i8* %p, align 4
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; CHECK-NEXT: %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %p)
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; CHECK-NEXT: store i8 3, i8* %p, align 4
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; CHECK-NEXT: ret void
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}
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; FIXME: We should be able to remove the first store to p, even though p and q
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; may alias.
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define void @test2(i8* %p, i8* %q) {
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store i8 1, i8* %p, align 4
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store i8 2, i8* %q, align 4
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%i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %q)
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store i8 3, i8* %p, align 4
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ret void
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; CHECK-LABEL: @test2(
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; CHECK-NEXT: store i8 1, i8* %p, align 4
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; CHECK-NEXT: store i8 2, i8* %q, align 4
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; CHECK-NEXT: %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %q)
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; CHECK-NEXT: store i8 3, i8* %p, align 4
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; CHECK-NEXT: ret void
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}
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