constant fold sign_extend_inreg
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28151 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 4809db4..60a749d 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1335,6 +1335,14 @@
ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.Val);
ConstantSDNode *N2C = dyn_cast<ConstantSDNode>(N2.Val);
if (N1C) {
+ if (Opcode == ISD::SIGN_EXTEND_INREG) {
+ int64_t Val = N1C->getValue();
+ unsigned FromBits = MVT::getSizeInBits(cast<VTSDNode>(N2)->getVT());
+ Val <<= 64-FromBits;
+ Val >>= 64-FromBits;
+ return getConstant(Val, VT);
+ }
+
if (N2C) {
uint64_t C1 = N1C->getValue(), C2 = N2C->getValue();
switch (Opcode) {
@@ -1441,7 +1449,7 @@
}
}
- // Fold a bunch of operators that
+ // Fold a bunch of operators when the RHS is undef.
if (N2.getOpcode() == ISD::UNDEF) {
switch (Opcode) {
case ISD::ADD: