[llvm-commits] [llvm] r138967 - in /llvm/trunk/lib/Transforms: InstCombine/InstructionCombining.cpp Scalar/SCCP.cpp

[Bill Wendling]

Author: void
Date: Thu Sep  1 16:28:33 2011
New Revision: 138967

URL: http://llvm.org/viewvc/llvm-project?rev=138967&view=rev
Log:
Change worklist driven deletion to be an iterative process.
Duncan noticed this!

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
    llvm/trunk/lib/Transforms/Scalar/SCCP.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=138967&r1=138966&r2=138967&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Thu Sep  1 16:28:33 2011
@@ -1573,41 +1573,20 @@
     // the instcombine code from having to deal with some bad special cases.
     for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
       if (!Visited.count(BB)) {
-        Instruction *Term = BB->getTerminator();
-
-        if (isa<TerminatorInst>(BB->begin()))
-          continue;
-
         // Delete the instructions backwards, as it has a reduced likelihood of
         // having to update as many def-use and use-def chains.
-        std::vector<Instruction*> WorkList;
-        WorkList.reserve(BB->size());
-        BasicBlock::iterator I = Term; --I;
-
-        while (true) {
-          if (!I->getType()->isVoidTy())
-            I->replaceAllUsesWith(UndefValue::get(I->getType()));
-          WorkList.push_back(I);
-          if (I == BB->begin())
+        for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
+          Instruction *Inst = &*I++;
+          if (isa<TerminatorInst>(Inst))
             break;
-          --I;
-        }
-
-        for (std::vector<Instruction*>::iterator
-               II = WorkList.begin(), IE = WorkList.end(); II != IE; ++II) {
-          Instruction *Inst = *II;
-          // Don't remove the landing pad. It should be removed only when its
-          // invokes are removed.
+          if (!Inst->use_empty())
+            Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
           if (isa<LandingPadInst>(Inst))
             continue;
-
-          // A debug intrinsic shouldn't force another iteration if we weren't
-          // going to do one without it.
           if (!isa<DbgInfoIntrinsic>(Inst)) {
             ++NumDeadInst;
             MadeIRChange = true;
           }
-
           Inst->eraseFromParent();
         }
       }

Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SCCP.cpp?rev=138967&r1=138966&r2=138967&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Thu Sep  1 16:28:33 2011
@@ -1688,24 +1688,15 @@
 
   // Delete the instructions backwards, as it has a reduced likelihood of
   // having to update as many def-use and use-def chains.
-  std::vector<Instruction*> WorkList;
-  WorkList.reserve(BB->size());
-  BasicBlock::iterator I = --BasicBlock::iterator(BB->getTerminator());
-
-  while (true) {
-    if (!I->use_empty())
-      I->replaceAllUsesWith(UndefValue::get(I->getType()));
-    WorkList.push_back(I);
-    if (I == BB->begin())
+  for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
+    Instruction *Inst = &*I++;
+    if (isa<TerminatorInst>(Inst))
       break;
-    --I;
-  }
-
-  for (std::vector<Instruction*>::iterator
-         II = WorkList.begin(), IE = WorkList.end(); II != IE; ++II) {
-    if (isa<LandingPadInst>(*II))
+    if (!Inst->use_empty())
+      Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
+    if (isa<LandingPadInst>(Inst))
       continue;
-    BB->getInstList().erase(*II);
+    BB->getInstList().erase(Inst);
     ++NumInstRemoved;
   }
 }