Revert rev. 63876. It is causing llvm-gcc bootstrap failure.

[oota-llvm.git] / lib / Transforms / Scalar / CondPropagate.cpp

diff --git a/lib/Transforms/Scalar/CondPropagate.cpp b/lib/Transforms/Scalar/CondPropagate.cpp
index 2e899432909e32e502bea65c93090b2adf295d7e..c4e2b1a40172d2d338712abc9b5b3b0b6e078ef1 100644 (file)
--- a/lib/Transforms/Scalar/CondPropagate.cpp
+++ b/lib/Transforms/Scalar/CondPropagate.cpp
@@ -23,6 +23,7 @@
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Streams.h"
 using namespace llvm;
@@ -44,6 +45,7 @@ namespace {
 
   private:
     bool MadeChange;
+    SmallVector<BasicBlock *, 4> DeadBlocks;
     void SimplifyBlock(BasicBlock *BB);
     void SimplifyPredecessors(BranchInst *BI);
     void SimplifyPredecessors(SwitchInst *SI);
@@ -60,14 +62,22 @@ FunctionPass *llvm::createCondPropagationPass() {
 
 bool CondProp::runOnFunction(Function &F) {
   bool EverMadeChange = false;
+  DeadBlocks.clear();
 
   // While we are simplifying blocks, keep iterating.
   do {
     MadeChange = false;
-    for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
-      SimplifyBlock(BB);
+    for (Function::iterator BB = F.begin(), E = F.end(); BB != E;)
+      SimplifyBlock(BB++);
     EverMadeChange = EverMadeChange || MadeChange;
   } while (MadeChange);
+
+  if (EverMadeChange) {
+    while (!DeadBlocks.empty()) {
+      BasicBlock *BB = DeadBlocks.back(); DeadBlocks.pop_back();
+      DeleteDeadBlock(BB);
+    }
+  }
   return EverMadeChange;
 }
 
@@ -111,8 +121,9 @@ void CondProp::SimplifyBlock(BasicBlock *BB) {
 
       // Succ is now dead, but we cannot delete it without potentially
       // invalidating iterators elsewhere.  Just insert an unreachable
-      // instruction in it.
+      // instruction in it and delete this block later on.
       new UnreachableInst(Succ);
+      DeadBlocks.push_back(Succ);
       MadeChange = true;
     }
 }
@@ -126,6 +137,14 @@ void CondProp::SimplifyPredecessors(BranchInst *BI) {
   // one use (the branch), and is the only instruction besides the branch in the
   // block.
   PHINode *PN = cast<PHINode>(BI->getCondition());
+
+  if (PN->getNumIncomingValues() == 1) {
+    // Eliminate single-entry PHI nodes.
+    FoldSingleEntryPHINodes(PN->getParent());
+    return;
+  }
+  
+  
   if (!PN->hasOneUse()) return;
 
   BasicBlock *BB = BI->getParent();