[llvm-commits] [PATCH] [msan] Remove unreachable bb's
Evgeniy Stepanov
eugenis at google.com
Mon Dec 17 07:25:15 PST 2012
PTAL.
The new removeUnreachableBlocks (it's second part) looks almost entirely like DeleteDeadBlock - the only difference is it does not removePredecessor from other unreachable blocks.
Hi kcc, chandlerc,
http://llvm-reviews.chandlerc.com/D208
CHANGE SINCE LAST DIFF
http://llvm-reviews.chandlerc.com/D208?vs=523&id=530#toc
Files:
lib/Transforms/Instrumentation/MemorySanitizer.cpp
lib/Transforms/Utils/Local.cpp
include/llvm/Transforms/Utils/Local.h
Index: lib/Transforms/Instrumentation/MemorySanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -67,6 +67,7 @@
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "llvm/Type.h"
@@ -478,6 +479,13 @@
bool runOnFunction() {
MS.initializeCallbacks(*F.getParent());
if (!MS.TD) return false;
+
+ // In the presence of unreachable blocks, we may see Phi nodes with
+ // incoming nodes from such blocks. Since InstVisitor skips unreachable
+ // blocks, such nodes will not have any shadow value associated with them.
+ // It's easier to remove unreachable blocks than deal with missing shadow.
+ removeUnreachableBlocks(F);
+
// Iterate all BBs in depth-first order and create shadow instructions
// for all instructions (where applicable).
// For PHI nodes we create dummy shadow PHIs which will be finalized later.
Index: lib/Transforms/Utils/Local.cpp
===================================================================
--- lib/Transforms/Utils/Local.cpp
+++ lib/Transforms/Utils/Local.cpp
@@ -15,6 +15,7 @@
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
@@ -963,3 +964,45 @@
DDI->eraseFromParent();
return true;
}
+
+/// RemoveUnreachableBlocks - Remove all blocks that can not be reached from the
+/// function's entry.
+void llvm::removeUnreachableBlocks(Function &F) {
+ SmallPtrSet<BasicBlock*, 128> Reachable;
+ SmallVector<BasicBlock*, 128> Worklist;
+ Worklist.push_back(&F.getEntryBlock());
+ Reachable.insert(&F.getEntryBlock());
+ do {
+ BasicBlock *BB = Worklist.pop_back_val();
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+ if (Reachable.insert(*SI))
+ Worklist.push_back(*SI);
+ } while (!Worklist.empty());
+
+ if (Reachable.size() == F.size())
+ return;
+
+ assert(Reachable.size() < F.size());
+ for (Function::iterator BB = llvm::next(F.begin()), E = F.end();
+ BB != E; ++BB) {
+ if (Reachable.count(BB))
+ continue;
+
+ // Remove BB as predecessor of all its reachable successors.
+ // Unreachable successors don't matter as they'll soon be removed, too.
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+ if (Reachable.count(*SI))
+ (*SI)->removePredecessor(BB);
+
+ // Zap all instructions in BB.
+ while (!BB->empty()) {
+ Instruction &I = BB->back();
+ if (!I.use_empty())
+ I.replaceAllUsesWith(UndefValue::get(I.getType()));
+ BB->getInstList().pop_back();
+ }
+
+ --BB;
+ llvm::next(BB)->eraseFromParent();
+ }
+}
Index: include/llvm/Transforms/Utils/Local.h
===================================================================
--- include/llvm/Transforms/Utils/Local.h
+++ include/llvm/Transforms/Utils/Local.h
@@ -257,6 +257,10 @@
bool replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
DIBuilder &Builder);
+/// \\brief - Remove all blocks that can not be reached from the function's
+/// entry.
+void removeUnreachableBlocks(Function &F);
+
} // End llvm namespace
#endif
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