Don't copy the operand of a SwitchInst into virtual registers as

eagerly. This helps avoid CopyToReg nodes in some cases where they
aren't needed, and also helps subsequent optimizer heuristics
in cases where the extra nodes would cause the node to appear
to have multiple results. This doesn't have a significant impact
currently; it'll help an upcoming change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68667 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
index ba59906b6da7afc954e42d3ce78918009f6db0fd..fd15603d9901e4283af4ffe7ed9f0b75d68bd3cd 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
@@ -243,9 +243,7 @@ static bool isUsedOutsideOfDefiningBlock(Instruction *I) {
   if (isa<PHINode>(I)) return true;
   BasicBlock *BB = I->getParent();
   for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; ++UI)
-    if (cast<Instruction>(*UI)->getParent() != BB || isa<PHINode>(*UI) ||
-        // FIXME: Remove switchinst special case.
-        isa<SwitchInst>(*UI))
+    if (cast<Instruction>(*UI)->getParent() != BB || isa<PHINode>(*UI))
       return true;
   return false;
 }
@@ -1640,6 +1638,9 @@ bool SelectionDAGLowering::handleSmallSwitchRange(CaseRec& CR,
     if (I != E-1) {
       FallThrough = CurMF->CreateMachineBasicBlock(CurBlock->getBasicBlock());
       CurMF->insert(BBI, FallThrough);
+
+      // Put SV in a virtual register to make it available from the new blocks.
+      ExportFromCurrentBlock(SV);
     } else {
       // If the last case doesn't match, go to the default block.
       FallThrough = Default;
@@ -1874,6 +1875,9 @@ bool SelectionDAGLowering::handleBTSplitSwitchCase(CaseRec& CR,
     TrueBB = CurMF->CreateMachineBasicBlock(LLVMBB);
     CurMF->insert(BBI, TrueBB);
     WorkList.push_back(CaseRec(TrueBB, C, CR.GE, LHSR));
+
+    // Put SV in a virtual register to make it available from the new blocks.
+    ExportFromCurrentBlock(SV);
   }
 
   // Similar to the optimization above, if the Value being switched on is
@@ -1888,6 +1892,9 @@ bool SelectionDAGLowering::handleBTSplitSwitchCase(CaseRec& CR,
     FalseBB = CurMF->CreateMachineBasicBlock(LLVMBB);
     CurMF->insert(BBI, FalseBB);
     WorkList.push_back(CaseRec(FalseBB,CR.LT,C,RHSR));
+
+    // Put SV in a virtual register to make it available from the new blocks.
+    ExportFromCurrentBlock(SV);
   }
 
   // Create a CaseBlock record representing a conditional branch to
@@ -2013,6 +2020,9 @@ bool SelectionDAGLowering::handleBitTestsSwitchCase(CaseRec& CR,
     BTC.push_back(BitTestCase(CasesBits[i].Mask,
                               CaseBB,
                               CasesBits[i].BB));
+
+    // Put SV in a virtual register to make it available from the new blocks.
+    ExportFromCurrentBlock(SV);
   }
 
   BitTestBlock BTB(lowBound, cmpRange, SV,