Fix a bug in the unreachable block elim pass. Dropping all references on a
basic block clear()'s all of the operands lists, including phis. This
caused removePredecessor to get confused later. Because of this, we just
nuke (without prejudice) PHI nodes in unreachable blocks.
llvm-svn: 14635
diff --git a/llvm/lib/CodeGen/UnreachableBlockElim.cpp b/llvm/lib/CodeGen/UnreachableBlockElim.cpp
index bcc1245..1b59ac4 100644
--- a/llvm/lib/CodeGen/UnreachableBlockElim.cpp
+++ b/llvm/lib/CodeGen/UnreachableBlockElim.cpp
@@ -21,6 +21,8 @@
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
+#include "llvm/iPHINode.h"
+#include "llvm/Constant.h"
#include "llvm/Function.h"
#include "llvm/Pass.h"
#include "llvm/Support/CFG.h"
@@ -52,10 +54,15 @@
std::vector<BasicBlock*> DeadBlocks;
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
if (!Reachable.count(I)) {
- DeadBlocks.push_back(I);
- for (succ_iterator SI = succ_begin(&*I), E = succ_end(&*I); SI != E; ++SI)
- (*SI)->removePredecessor(I);
- I->dropAllReferences();
+ BasicBlock *BB = I;
+ DeadBlocks.push_back(BB);
+ while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
+ PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
+ BB->getInstList().pop_front();
+ }
+ for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
+ (*SI)->removePredecessor(BB);
+ BB->dropAllReferences();
}
if (DeadBlocks.empty()) return false;