Fix bug: test/Regression/Other/2002-03-11-ConstPropCrash.ll

llvm-svn: 1858

include/llvm/Transforms/Scalar/ConstantProp.h

@@ -23,9 +23,11 @@ bool doConstantPropogation(BasicBlock *BB, BasicBlock::iterator &I);
 
 // ConstantFoldTerminator - If a terminator instruction is predicated on a
 // constant value, convert it into an unconditional branch to the constant
-// destination.
+// destination.  This is a nontrivial operation because the successors of this
+// basic block must have their PHI nodes updated.
 //
-bool ConstantFoldTerminator(TerminatorInst *T);
+bool ConstantFoldTerminator(BasicBlock *BB, BasicBlock::iterator &I,
+                            TerminatorInst *T);
 
 
 //===----------------------------------------------------------------------===//

lib/Transforms/Scalar/ConstantProp.cpp

@@ -102,7 +102,8 @@ ConstantFoldBinaryInst(BasicBlock *BB, BasicBlock::iterator &II,
 // constant value, convert it into an unconditional branch to the constant
 // destination.
 //
-bool ConstantFoldTerminator(TerminatorInst *T) {
+bool ConstantFoldTerminator(BasicBlock *BB, BasicBlock::iterator &II,
+                            TerminatorInst *T) {
   // Branch - See if we are conditional jumping on constant
   if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
     if (BI->isUnconditional()) return false;  // Can't optimize uncond branch
@@ -127,6 +128,7 @@ bool ConstantFoldTerminator(TerminatorInst *T) {
       // Set the unconditional destination, and change the insn to be an
       // unconditional branch.
       BI->setUnconditionalDest(Destination);
+      II = BB->end()-1;  // Update instruction iterator!
       return true;
     }
 #if 0
@@ -171,7 +173,7 @@ bool doConstantPropogation(BasicBlock *BB, BasicBlock::iterator &II) {
     Constant *D = dyn_cast<Constant>(UInst->getOperand(0));
     if (D) return ConstantFoldUnaryInst(BB, II, UInst, D);
   } else if (TerminatorInst *TInst = dyn_cast<TerminatorInst>(Inst)) {
-    return ConstantFoldTerminator(TInst);
+    return ConstantFoldTerminator(BB, II, TInst);
 
   } else if (PHINode *PN = dyn_cast<PHINode>(Inst)) {
     // If it's a PHI node and only has one operand

lib/Transforms/Scalar/SCCP.cpp

@@ -270,7 +270,7 @@ bool SCCP::doSCCP() {
         // Hey, we just changed something!
         MadeChanges = true;
       } else if (TerminatorInst *TI = dyn_cast<TerminatorInst>(Inst)) {
-        MadeChanges |= ConstantFoldTerminator(TI);
+        MadeChanges |= ConstantFoldTerminator(BB, BI, TI);
       }
 
       ++BI;