[llvm-commits] CVS: llvm/lib/CodeGen/UnreachableBlockElim.cpp

[Chris Lattner]

Changes in directory llvm/lib/CodeGen:

UnreachableBlockElim.cpp updated: 1.1 -> 1.2

---
Log message:

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.


---
Diffs of the changes:  (+11 -4)

Index: llvm/lib/CodeGen/UnreachableBlockElim.cpp
diff -u llvm/lib/CodeGen/UnreachableBlockElim.cpp:1.1 llvm/lib/CodeGen/UnreachableBlockElim.cpp:1.2
--- llvm/lib/CodeGen/UnreachableBlockElim.cpp:1.1	Fri Jul  2 00:46:10 2004
+++ llvm/lib/CodeGen/UnreachableBlockElim.cpp	Tue Jul  6 01:36:11 2004
@@ -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;