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| author | Sanjoy Das <sanjoy@playingwithpointers.com> | 2018-02-20 23:19:34 +0000 |
|---|---|---|
| committer | Sanjoy Das <sanjoy@playingwithpointers.com> | 2018-02-20 23:19:34 +0000 |
| commit | 737fa40ffad15482801cc60271aed40dd5de9c95 (patch) | |
| tree | 66826396d645129f6ea4426e8ea4826f3985a9ef /llvm/test/Transforms | |
| parent | 6cd4861c22ef078c2a043ac6ffb1a4467dd85534 (diff) | |
| download | bcm5719-llvm-737fa40ffad15482801cc60271aed40dd5de9c95.tar.gz bcm5719-llvm-737fa40ffad15482801cc60271aed40dd5de9c95.zip | |
[DSE] Don't DSE stores that subsequent memmove calls read from
Summary:
We used to remove the first memmove in cases like this:
memmove(p, p+2, 8);
memmove(p, p+2, 8);
which is incorrect. Fix this by changing isPossibleSelfRead to what was most
likely the intended behavior.
Historical note: the buggy code was added in https://reviews.llvm.org/rL120974
to address PR8728.
Reviewers: rsmith
Subscribers: mcrosier, llvm-commits, jlebar
Differential Revision: https://reviews.llvm.org/D43425
llvm-svn: 325641
Diffstat (limited to 'llvm/test/Transforms')
| -rw-r--r-- | llvm/test/Transforms/DeadStoreElimination/simple.ll | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/llvm/test/Transforms/DeadStoreElimination/simple.ll b/llvm/test/Transforms/DeadStoreElimination/simple.ll index 6130fbbf807..604621130e0 100644 --- a/llvm/test/Transforms/DeadStoreElimination/simple.ll +++ b/llvm/test/Transforms/DeadStoreElimination/simple.ll @@ -252,6 +252,9 @@ define void @test17v(i8* %P, i8* %Q) nounwind ssp { ; Do not delete instruction where possible situation is: ; A = B ; A = A +; +; NB! See PR11763 - currently LLVM allows memcpy's source and destination to be +; equal (but not inequal and overlapping). define void @test18(i8* %P, i8* %Q, i8* %R) nounwind ssp { tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i1 false) @@ -521,3 +524,51 @@ define void @test35(i32* noalias %p) { store i32 0, i32* %p ret void } + +; We cannot optimize away the first memmove since %P could overlap with %Q. +define void @test36(i8* %P, i8* %Q) { +; CHECK-LABEL: @test36( +; CHECK-NEXT: tail call void @llvm.memmove.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) +; CHECK-NEXT: tail call void @llvm.memmove.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) +; CHECK-NEXT: ret + + tail call void @llvm.memmove.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) + tail call void @llvm.memmove.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) + ret void +} + +define void @test37(i8* %P, i8* %Q, i8* %R) { +; CHECK-LABEL: @test37( +; CHECK-NEXT: tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) +; CHECK-NEXT: tail call void @llvm.memmove.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i1 false) +; CHECK-NEXT: ret + + tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) + tail call void @llvm.memmove.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i1 false) + ret void +} + +; Same caveat about memcpy as in @test18 applies here. +define void @test38(i8* %P, i8* %Q, i8* %R) { +; CHECK-LABEL: @test38( +; CHECK-NEXT: tail call void @llvm.memmove.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) +; CHECK-NEXT: tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i1 false) +; CHECK-NEXT: ret + + tail call void @llvm.memmove.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) + tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i1 false) + ret void +} + +define void @test39(i8* %P, i8* %Q, i8* %R) { +; CHECK-LABEL: @test39( +; CHECK-NEXT: tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) +; CHECK-NEXT: tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 8, i1 false) +; CHECK-NEXT: ret + + tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i1 false) + tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 8, i1 false) + ret void +} + +declare void @llvm.memmove.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i1) |
