[JumpThreading] Don't forget to report that the IR changed
authorDavid Majnemer <david.majnemer@gmail.com>
Sun, 10 Jan 2016 07:13:04 +0000 (07:13 +0000)
committerDavid Majnemer <david.majnemer@gmail.com>
Sun, 10 Jan 2016 07:13:04 +0000 (07:13 +0000)
JumpThreading's runOnFunction is supposed to return true if it made any
changes.  JumpThreading has a call to removeUnreachableBlocks which may
result in changes to the IR but runOnFunction didn't appropriate account
for this possibility, leading to badness.

While we are here, make sure to call LazyValueInfo::eraseBlock in
removeUnreachableBlocks;  JumpThreading preserves LVI.

This fixes PR26096.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257279 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Transforms/Utils/Local.h
lib/Transforms/Scalar/JumpThreading.cpp
lib/Transforms/Utils/Local.cpp

index 81b376f..911c6f1 100644 (file)
@@ -42,6 +42,7 @@ class TargetLibraryInfo;
 class TargetTransformInfo;
 class DIBuilder;
 class DominatorTree;
+class LazyValueInfo;
 
 template<typename T> class SmallVectorImpl;
 
@@ -303,7 +304,7 @@ void removeUnwindEdge(BasicBlock *BB);
 /// \brief Remove all blocks that can not be reached from the function's entry.
 ///
 /// Returns true if any basic block was removed.
-bool removeUnreachableBlocks(Function &F);
+bool removeUnreachableBlocks(Function &F, LazyValueInfo *LVI = nullptr);
 
 /// \brief Combine the metadata of two instructions so that K can replace J
 ///
index 35a10db..dcdcfed 100644 (file)
@@ -211,11 +211,12 @@ bool JumpThreading::runOnFunction(Function &F) {
   // we will loop forever. We take care of this issue by not jump threading for
   // back edges. This works for normal cases but not for unreachable blocks as
   // they may have cycle with no back edge.
-  removeUnreachableBlocks(F);
+  bool EverChanged = false;
+  EverChanged |= removeUnreachableBlocks(F, LVI);
 
   FindLoopHeaders(F);
 
-  bool Changed, EverChanged = false;
+  bool Changed;
   do {
     Changed = false;
     for (Function::iterator I = F.begin(), E = F.end(); I != E;) {
index 0e386ac..e4310c7 100644 (file)
@@ -23,6 +23,7 @@
 #include "llvm/Analysis/EHPersonalities.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/Analysis/LazyValueInfo.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/CFG.h"
 #include "llvm/IR/Constants.h"
@@ -1407,7 +1408,7 @@ void llvm::removeUnwindEdge(BasicBlock *BB) {
 /// removeUnreachableBlocksFromFn - Remove blocks that are not reachable, even
 /// if they are in a dead cycle.  Return true if a change was made, false
 /// otherwise.
-bool llvm::removeUnreachableBlocks(Function &F) {
+bool llvm::removeUnreachableBlocks(Function &F, LazyValueInfo *LVI) {
   SmallPtrSet<BasicBlock*, 128> Reachable;
   bool Changed = markAliveBlocks(F, Reachable);
 
@@ -1428,6 +1429,8 @@ bool llvm::removeUnreachableBlocks(Function &F) {
          ++SI)
       if (Reachable.count(*SI))
         (*SI)->removePredecessor(&*BB);
+    if (LVI)
+      LVI->eraseBlock(&*BB);
     BB->dropAllReferences();
   }