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

3 files changed, 80 insertions, 0 deletions

diff --git a/test/Transforms/DeadStoreElimination/lifetime.ll b/test/Transforms/DeadStoreElimination/lifetime.ll
new file mode 100644
index 0000000..b2da790
--- /dev/null
+++ b/test/Transforms/DeadStoreElimination/lifetime.ll
@@ -0,0 +1,19 @@
+; RUN: opt -S -dse < %s | FileCheck %s
+
+declare void @llvm.lifetime.end(i64, i8*)
+declare void @llvm.memset.i8(i8*, i8, i8, i32)
+
+define void @test1() {
+; CHECK: @test1
+  %A = alloca i8
+
+  store i8 0, i8* %A  ;; Written to by memset
+  call void @llvm.lifetime.end(i64 1, i8* %A)
+; CHECK: lifetime.end
+
+  call void @llvm.memset.i8(i8* %A, i8 0, i8 -1, i32 0)
+; CHECK-NOT: memset
+
+  ret void
+; CHECK: ret void
+}
diff --git a/test/Transforms/DeadStoreElimination/memintrinsics.ll b/test/Transforms/DeadStoreElimination/memintrinsics.ll
new file mode 100644
index 0000000..e31e9fa
--- /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
+}
diff --git a/test/Transforms/DeadStoreElimination/partial-overwrite.ll b/test/Transforms/DeadStoreElimination/partial-overwrite.ll
new file mode 100644
index 0000000..048d464
--- /dev/null
+++ b/test/Transforms/DeadStoreElimination/partial-overwrite.ll
@@ -0,0 +1,14 @@
+; RUN: opt -dse -S %s | FileCheck %s
+; Note that we could do better by merging the two stores into one.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @test(i32* %P) {
+  store i32 0, i32* %P
+; CHECK: store i32
+  %Q = bitcast i32* %P to i16*
+  store i16 1, i16* %Q
+; CHECK: store i16
+  ret void
+}