X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FStrongPHIElimination.cpp;h=cdf827d50e6e9b055f4f2119a5fb36cf2f1ba2f4;hb=527c250a9080a5b6cf0053a6215037c3769ff4a0;hp=e5cae2bc723bf14c396f47c380098b5b3d22ecb9;hpb=ddd060ffcfd56ef91eb28ce76a2b0576dfe51129;p=oota-llvm.git

diff --git a/lib/CodeGen/StrongPHIElimination.cpp b/lib/CodeGen/StrongPHIElimination.cpp
index e5cae2bc723..cdf827d50e6 100644
--- a/lib/CodeGen/StrongPHIElimination.cpp
+++ b/lib/CodeGen/StrongPHIElimination.cpp
@@ -550,7 +550,12 @@ void StrongPHIElimination::processPHIUnion(MachineInstr* Inst,
     for (DomForestNode::iterator CI = DFNode->begin(), CE = DFNode->end();
          CI != CE; ++CI) {
       DomForestNode* child = *CI;   
-        
+      
+      // If the current node is live-out of the defining block of one of its
+      // children, insert a copy for it.  NOTE: The paper actually calls for
+      // a more elaborate heuristic for determining whether to insert copies
+      // for the child or the parent.  In the interest of simplicity, we're
+      // just always choosing the parent.
       if (isLiveOut(DFNode->getReg(),
           MRI.getVRegDef(child->getReg())->getParent(), MRI, LV)) {
         // Insert copies for parent
@@ -565,6 +570,9 @@ void StrongPHIElimination::processPHIUnion(MachineInstr* Inst,
             PHIUnion.erase(SrcReg);
           }
         }
+      
+      // If a node is live-in to the defining block of one of its children, but
+      // not live-out, then we need to scan that block for local interferences.
       } else if (isLiveIn(DFNode->getReg(),
                           MRI.getVRegDef(child->getReg())->getParent(),
                           MRI, LV) ||
@@ -743,11 +751,17 @@ bool StrongPHIElimination::runOnMachineFunction(MachineFunction &Fn) {
   // FIXME: Insert last-minute copies
   
   // Remove PHIs
-  for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)
+  std::vector<MachineInstr*> phis;
+  for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
     for (MachineBasicBlock::iterator BI = I->begin(), BE = I->end();
          BI != BE; ++BI)
       if (BI->getOpcode() == TargetInstrInfo::PHI)
-        BI->eraseFromParent();
+        phis.push_back(BI);
+  }
+  
+  for (std::vector<MachineInstr*>::iterator I = phis.begin(), E = phis.end();
+       I != E; ++I)
+    (*I)->eraseFromParent();
   
   return false;
 }