[llvm-commits] [llvm] r139090 - in /llvm/trunk/lib/Transforms: InstCombine/InstructionCombining.cpp Scalar/SCCP.cpp

[Bill Wendling]

Author: void
Date: Sun Sep  4 04:43:36 2011
New Revision: 139090

URL: http://llvm.org/viewvc/llvm-project?rev=139090&view=rev
Log:
Use Duncan's patch to delete the instructions in reverse order (minus the landingpad and terminator).

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=139090&r1=139089&r2=139090&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Sun Sep  4 04:43:36 2011
@@ -1574,15 +1574,19 @@
     for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
       if (Visited.count(BB)) continue;
 
-      // Delete the instructions.
-      for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
-        Instruction *Inst = &*I++;
-        if (isa<TerminatorInst>(Inst))
-          break;
+      // Delete the instructions backwards, as it has a reduced likelihood of
+      // having to update as many def-use and use-def chains.
+      Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
+      while (EndInst != BB->begin()) {
+        // Delete the next to last instruction.
+        BasicBlock::iterator I = EndInst;
+        Instruction *Inst = --I;
         if (!Inst->use_empty())
           Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
-        if (isa<LandingPadInst>(Inst))
+        if (isa<LandingPadInst>(Inst)) {
+          EndInst = Inst;
           continue;
+        }
         if (!isa<DbgInfoIntrinsic>(Inst)) {
           ++NumDeadInst;
           MadeIRChange = true;

Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SCCP.cpp?rev=139090&r1=139089&r2=139090&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Sun Sep  4 04:43:36 2011
@@ -1686,15 +1686,19 @@
   if (isa<TerminatorInst>(BB->begin()))
     return;
 
-  // Delete the instructions.
-  for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
-    Instruction *Inst = &*I++;
-    if (isa<TerminatorInst>(Inst))
-      break;
+  // Delete the instructions backwards, as it has a reduced likelihood of having
+  // to update as many def-use and use-def chains.
+  Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
+  while (EndInst != BB->begin()) {
+    // Delete the next to last instruction.
+    BasicBlock::iterator I = EndInst;
+    Instruction *Inst = --I;
     if (!Inst->use_empty())
       Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
-    if (isa<LandingPadInst>(Inst))
+    if (isa<LandingPadInst>(Inst)) {
+      EndInst = Inst;
       continue;
+    }
     BB->getInstList().erase(Inst);
     ++NumInstRemoved;
   }