Use COPY for fast-isel bitconvert, but don't create cross-class copies.

This doesn't change the behavior of SelectBitcast for X86.

llvm-svn: 108073

1 files changed, 6 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 63413d77cf2..3f7e4a5fac4 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -671,13 +671,12 @@ bool FastISel::SelectBitCast(const User *I) {
   if (SrcVT.getSimpleVT() == DstVT.getSimpleVT()) {
     TargetRegisterClass* SrcClass = TLI.getRegClassFor(SrcVT);
     TargetRegisterClass* DstClass = TLI.getRegClassFor(DstVT);
-    ResultReg = createResultReg(DstClass);
-    
-    bool InsertedCopy = TII.copyRegToReg(*FuncInfo.MBB, FuncInfo.InsertPt,
-                                         ResultReg, Op0,
-                                         DstClass, SrcClass, DL);
-    if (!InsertedCopy)
-      ResultReg = 0;
+    // Don't attempt a cross-class copy. It will likely fail.
+    if (SrcClass == DstClass) {
+      ResultReg = createResultReg(DstClass);
+      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
+              ResultReg).addReg(Op0);
+    }
   }
   
   // If the reg-reg copy failed, select a BIT_CONVERT opcode.