MemCpyOpt: Turn memcpys from a constant into a memset if possible.
This allows us to compile "int cst[] = {-1, -1, -1};" into
movl $-1, 16(%rsp)
movq $-1, 8(%rsp)
instead of
movl _cst+8(%rip), %eax
movl %eax, 16(%rsp)
movq _cst(%rip), %rax
movq %rax, 8(%rsp)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122548 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Transforms/MemCpyOpt/memcpy-to-memset.ll b/test/Transforms/MemCpyOpt/memcpy-to-memset.ll
new file mode 100644
index 0000000..b18d176
--- /dev/null
+++ b/test/Transforms/MemCpyOpt/memcpy-to-memset.ll
@@ -0,0 +1,19 @@
+; RUN: opt -memcpyopt -S < %s | FileCheck %s
+
+@cst = internal constant [3 x i32] [i32 -1, i32 -1, i32 -1], align 4
+
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
+declare void @foo(i32*) nounwind
+
+define void @test1() nounwind {
+ %arr = alloca [3 x i32], align 4
+ %arr_i8 = bitcast [3 x i32]* %arr to i8*
+ call void @llvm.memcpy.p0i8.p0i8.i64(i8* %arr_i8, i8* bitcast ([3 x i32]* @cst to i8*), i64 12, i32 4, i1 false)
+ %arraydecay = getelementptr inbounds [3 x i32]* %arr, i64 0, i64 0
+ call void @foo(i32* %arraydecay) nounwind
+ ret void
+; CHECK: @test1
+; CHECK: call void @llvm.memset
+; CHECK-NOT: call void @llvm.memcpy
+; CHECK: ret void
+}