From fcd2e94eccdb05f675a72ec6cbd40024cb485b12 Mon Sep 17 00:00:00 2001
From: Juergen Ributzka <juergen@apple.com>
Date: Wed, 2 Apr 2014 22:21:01 +0000
Subject: [PATCH] Add comments and test case for [DAG] Keep the opaque constant
 flag when performing unary constant folding operations (r204737).

llvm-svn: 205474
---
 llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp |  6 +++++-
 llvm/test/CodeGen/X86/const-base-addr.ll       | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/X86/const-base-addr.ll

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 5280623..d11ce80 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2535,7 +2535,11 @@ SDValue SelectionDAG::getNode(unsigned Opcode, SDLoc DL, EVT VT) {
 
 SDValue SelectionDAG::getNode(unsigned Opcode, SDLoc DL,
                               EVT VT, SDValue Operand) {
-  // Constant fold unary operations with an integer constant operand.
+  // Constant fold unary operations with an integer constant operand. Even
+  // opaque constant will be folded, because the folding of unary operations
+  // doesn't create new constants with different values. Nevertheless, the
+  // opaque flag is preserved during folding to prevent future folding with
+  // other constants.
   if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Operand.getNode())) {
     const APInt &Val = C->getAPIntValue();
     switch (Opcode) {
diff --git a/llvm/test/CodeGen/X86/const-base-addr.ll b/llvm/test/CodeGen/X86/const-base-addr.ll
new file mode 100644
index 0000000..f859d7fa
--- /dev/null
+++ b/llvm/test/CodeGen/X86/const-base-addr.ll
@@ -0,0 +1,24 @@
+; RUN: llc < %s | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.9.0"
+
+%T = type { i32, i32, i32, i32 }
+
+define i32 @test1() nounwind {
+; CHECK-LABEL:  test1
+; CHECK:        movabsq $123456789012345678, %rcx
+; CHECK-NEXT:   movl  4(%rcx), %eax
+; CHECK-NEXT:   addl  8(%rcx), %eax
+; CHECK-NEXT:   addl  12(%rcx), %eax
+  %addr1 = getelementptr %T* inttoptr (i64 123456789012345678 to %T*), i32 0, i32 1
+  %tmp1 = load i32* %addr1
+  %addr2 = getelementptr %T* inttoptr (i64 123456789012345678 to %T*), i32 0, i32 2
+  %tmp2 = load i32* %addr2
+  %addr3 = getelementptr %T* inttoptr (i64 123456789012345678 to %T*), i32 0, i32 3
+  %tmp3 = load i32* %addr3
+  %tmp4 = add i32 %tmp1, %tmp2
+  %tmp5 = add i32 %tmp3, %tmp4
+  ret i32 %tmp5
+}
+
-- 
2.7.4