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478de7c13b
Summary: Teach EarlyCSE about invariant.start intrinsic. Specifically, we can perform store-load, load-load forwarding over this call. Reviewers: majnemer, reames, dberlin, sanjoy Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D23268 llvm-svn: 278153
72 lines
2.0 KiB
LLVM
72 lines
2.0 KiB
LLVM
; RUN: opt < %s -S -early-cse | FileCheck %s
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; RUN: opt < %s -S -passes=early-cse | FileCheck %s
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declare {}* @llvm.invariant.start.p0i8(i64, i8* nocapture) nounwind readonly
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declare void @llvm.invariant.end.p0i8({}*, i64, i8* nocapture) nounwind
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; Check that we do load-load forwarding over invariant.start, since it does not
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; clobber memory
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define i8 @test1(i8 *%P) {
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; CHECK-LABEL: @test1(
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; CHECK-NEXT: %V1 = load i8, i8* %P
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; CHECK-NEXT: %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %P)
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; CHECK-NEXT: ret i8 0
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%V1 = load i8, i8* %P
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%i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %P)
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%V2 = load i8, i8* %P
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%Diff = sub i8 %V1, %V2
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ret i8 %Diff
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}
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; Trivial Store->load forwarding over invariant.start
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define i8 @test2(i8 *%P) {
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; CHECK-LABEL: @test2(
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; CHECK-NEXT: store i8 42, i8* %P
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; CHECK-NEXT: %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %P)
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; CHECK-NEXT: ret i8 42
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store i8 42, i8* %P
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%i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %P)
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%V1 = load i8, i8* %P
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ret i8 %V1
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}
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; We can DSE over invariant.start calls, since the first store to
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; %P is valid, and the second store is actually unreachable based on semantics
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; of invariant.start.
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define void @test3(i8* %P) {
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; CHECK-LABEL: @test3(
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; CHECK-NEXT: %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %P)
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; CHECK-NEXT: store i8 60, i8* %P
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store i8 50, i8* %P
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%i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %P)
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store i8 60, i8* %P
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ret void
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}
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; FIXME: Now the first store can actually be eliminated, since there is no read within
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; the invariant region, between start and end.
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define void @test4(i8* %P) {
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; CHECK-LABEL: @test4(
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; CHECK-NEXT: store i8 50, i8* %P
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; CHECK-NEXT: %i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %P)
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; CHECK-NEXT: call void @llvm.invariant.end.p0i8({}* %i, i64 1, i8* %P)
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; CHECK-NEXT: store i8 60, i8* %P
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store i8 50, i8* %P
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%i = call {}* @llvm.invariant.start.p0i8(i64 1, i8* %P)
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call void @llvm.invariant.end.p0i8({}* %i, i64 1, i8* %P)
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store i8 60, i8* %P
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ret void
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}
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