Commit a small improvement that is already in the x86 and ia64 backends to

not generate unnecessary register copies.  This improves compile time by
2-5% depending on the test.

llvm-svn: 22210

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPC32ISelPattern.cpp b/llvm/lib/Target/PowerPC/PPC32ISelPattern.cpp
index 750161caf8a..5b4c6e58d5c 100644
--- a/llvm/lib/Target/PowerPC/PPC32ISelPattern.cpp
+++ b/llvm/lib/Target/PowerPC/PPC32ISelPattern.cpp
@@ -1572,6 +1572,11 @@ unsigned ISel::SelectExpr(SDOperand N, bool Recording) {
   SDNode *Node = N.Val;
   MVT::ValueType DestType = N.getValueType();
 
+  if (Node->getOpcode() == ISD::CopyFromReg &&
+      MRegisterInfo::isVirtualRegister(cast<RegSDNode>(Node)->getReg()))
+    // Just use the specified register as our input.
+    return cast<RegSDNode>(Node)->getReg();
+
   unsigned &Reg = ExprMap[N];
   if (Reg) return Reg;