[llvm] r205474 - Add comments and test case for [DAG] Keep the opaque constant flag when performing unary constant folding operations (r204737).

[Juergen Ributzka]

Author: ributzka
Date: Wed Apr  2 17:21:01 2014
New Revision: 205474

URL: http://llvm.org/viewvc/llvm-project?rev=205474&view=rev
Log:
Add comments and test case for [DAG] Keep the opaque constant flag when performing unary constant folding operations (r204737).

Added:
    llvm/trunk/test/CodeGen/X86/const-base-addr.ll
Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=205474&r1=205473&r2=205474&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Wed Apr  2 17:21:01 2014
@@ -2535,7 +2535,11 @@ SDValue SelectionDAG::getNode(unsigned O
 
 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) {

Added: llvm/trunk/test/CodeGen/X86/const-base-addr.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/const-base-addr.ll?rev=205474&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/const-base-addr.ll (added)
+++ llvm/trunk/test/CodeGen/X86/const-base-addr.ll Wed Apr  2 17:21:01 2014
@@ -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
+}
+