Reapply r86359, "Teach dead store elimination that certain intrinsics write to

memory just like a store" with bug fixed (partial-overwrite.ll is the
regression test).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86667 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 47 insertions, 0 deletions

diff --git a/test/Transforms/DeadStoreElimination/memintrinsics.ll b/test/Transforms/DeadStoreElimination/memintrinsics.ll
new file mode 100644
index 0000000000..e31e9fa3ca
--- /dev/null
+++ b/test/Transforms/DeadStoreElimination/memintrinsics.ll
@@ -0,0 +1,47 @@
+; RUN: opt -S -dse < %s | FileCheck %s
+
+declare void @llvm.memcpy.i8(i8*, i8*, i8, i32)
+declare void @llvm.memmove.i8(i8*, i8*, i8, i32)
+declare void @llvm.memset.i8(i8*, i8, i8, i32)
+
+define void @test1() {
+; CHECK: @test1
+  %A = alloca i8
+  %B = alloca i8
+
+  store i8 0, i8* %A  ;; Written to by memcpy
+; CHECK-NOT: store
+
+  call void @llvm.memcpy.i8(i8* %A, i8* %B, i8 -1, i32 0)
+
+  ret void
+; CHECK: ret void
+}
+
+define void @test2() {
+; CHECK: @test2
+  %A = alloca i8
+  %B = alloca i8
+
+  store i8 0, i8* %A  ;; Written to by memmove
+; CHECK-NOT: store
+
+  call void @llvm.memmove.i8(i8* %A, i8* %B, i8 -1, i32 0)
+
+  ret void
+; CHECK: ret void
+}
+
+define void @test3() {
+; CHECK: @test3
+  %A = alloca i8
+  %B = alloca i8
+
+  store i8 0, i8* %A  ;; Written to by memset
+; CHECK-NOT: store
+
+  call void @llvm.memset.i8(i8* %A, i8 0, i8 -1, i32 0)
+
+  ret void
+; CHECK: ret void
+}