From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Sun, 11 Jul 2010 05:16:54 +0000 (+0000)
Subject: Use COPY for fast-isel bitconvert, but don't create cross-class copies.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e7917bb207d5178dfb26066f839e4c295fd3a1eb;p=oota-llvm.git

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

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108073 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index 63413d77cf2..3f7e4a5fac4 100644
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/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.