A memcpy out of an fresh alloca is a no-op, delete it. Patch by Patrick Walton!

llvm-svn: 200907

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/test/Transforms/MemCpyOpt/memcpy-undef.ll b/llvm/test/Transforms/MemCpyOpt/memcpy-undef.ll
new file mode 100644
index 00000000000..fd4965f4dc5
--- /dev/null
+++ b/llvm/test/Transforms/MemCpyOpt/memcpy-undef.ll
@@ -0,0 +1,25 @@
+; RUN: opt < %s -basicaa -memcpyopt -S | FileCheck %s
+
+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-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.8.0"
+
+%struct.foo = type { i8, [7 x i8], i32 }
+
+define i32 @test1(%struct.foo* nocapture %foobie) nounwind noinline ssp uwtable {
+  %bletch.sroa.1 = alloca [7 x i8], align 1
+  %1 = getelementptr inbounds %struct.foo* %foobie, i64 0, i32 0
+  store i8 98, i8* %1, align 4
+  %2 = getelementptr inbounds %struct.foo* %foobie, i64 0, i32 1, i64 0
+  %3 = getelementptr inbounds [7 x i8]* %bletch.sroa.1, i64 0, i64 0
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %2, i8* %3, i64 7, i32 1, i1 false)
+  %4 = getelementptr inbounds %struct.foo* %foobie, i64 0, i32 2
+  store i32 20, i32* %4, align 4
+  ret i32 undef
+
+; Check that the memcpy is removed.
+; CHECK-LABEL: @test1(
+; CHECK-NOT: call void @llvm.memcpy
+}
+
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
+