[msan] Remove unreachable blocks before instrumenting a function.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170883 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index 58d973a..58f3b75 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/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 +964,43 @@
DDI->eraseFromParent();
return true;
}
+
+bool llvm::removeUnreachableBlocks(Function &F) {
+ SmallPtrSet<BasicBlock*, 16> 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 false;
+
+ assert(Reachable.size() < F.size());
+ for (Function::iterator I = llvm::next(F.begin()), E = F.end(); I != E; ++I) {
+ if (Reachable.count(I))
+ continue;
+
+ // Remove the block 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(I), SE = succ_end(I); SI != SE; ++SI)
+ if (Reachable.count(*SI))
+ (*SI)->removePredecessor(I);
+
+ // Zap all instructions in this basic block.
+ while (!I->empty()) {
+ Instruction &Inst = I->back();
+ if (!Inst.use_empty())
+ Inst.replaceAllUsesWith(UndefValue::get(Inst.getType()));
+ I->getInstList().pop_back();
+ }
+
+ --I;
+ llvm::next(I)->eraseFromParent();
+ }
+ return true;
+}