It's not necessary to do rounding for alloca operations when the requested
alignment is equal to the stack alignment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/SimplifyCFG.cpp b/lib/Transforms/Scalar/SimplifyCFG.cpp
new file mode 100644
index 0000000..6b47ef7
--- /dev/null
+++ b/lib/Transforms/Scalar/SimplifyCFG.cpp
@@ -0,0 +1,145 @@
+//===- SimplifyCFG.cpp - CFG Simplification Pass --------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements dead code elimination and basic block merging.
+//
+// Specifically, this:
+// * removes basic blocks with no predecessors
+// * merges a basic block into its predecessor if there is only one and the
+// predecessor only has one successor.
+// * Eliminates PHI nodes for basic blocks with a single predecessor
+// * Eliminates a basic block that only contains an unconditional branch
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "simplifycfg"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
+#include "llvm/Module.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Pass.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
+using namespace llvm;
+
+STATISTIC(NumSimpl, "Number of blocks simplified");
+
+namespace {
+ struct VISIBILITY_HIDDEN CFGSimplifyPass : public FunctionPass {
+ static char ID; // Pass identification, replacement for typeid
+ CFGSimplifyPass() : FunctionPass((intptr_t)&ID) {}
+
+ virtual bool runOnFunction(Function &F);
+ };
+ char CFGSimplifyPass::ID = 0;
+ RegisterPass<CFGSimplifyPass> X("simplifycfg", "Simplify the CFG");
+}
+
+// Public interface to the CFGSimplification pass
+FunctionPass *llvm::createCFGSimplificationPass() {
+ return new CFGSimplifyPass();
+}
+
+static bool MarkAliveBlocks(BasicBlock *BB,
+ SmallPtrSet<BasicBlock*, 16> &Reachable) {
+
+ std::vector<BasicBlock*> Worklist;
+ Worklist.push_back(BB);
+ bool Changed = false;
+ while (!Worklist.empty()) {
+ BB = Worklist.back();
+ Worklist.pop_back();
+
+ if (!Reachable.insert(BB))
+ continue;
+
+ // Do a quick scan of the basic block, turning any obviously unreachable
+ // instructions into LLVM unreachable insts. The instruction combining pass
+ // canonnicalizes unreachable insts into stores to null or undef.
+ for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ++BBI)
+ if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
+ if (isa<ConstantPointerNull>(SI->getOperand(1)) ||
+ isa<UndefValue>(SI->getOperand(1))) {
+ // Loop over all of the successors, removing BB's entry from any PHI
+ // nodes.
+ for (succ_iterator I = succ_begin(BB), SE = succ_end(BB); I != SE;++I)
+ (*I)->removePredecessor(BB);
+
+ new UnreachableInst(SI);
+
+ // All instructions after this are dead.
+ while (BBI != E) {
+ if (!BBI->use_empty())
+ BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
+ BB->getInstList().erase(BBI++);
+ }
+ break;
+ }
+
+
+ Changed |= ConstantFoldTerminator(BB);
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
+ Worklist.push_back(*SI);
+ }
+ return Changed;
+}
+
+
+// It is possible that we may require multiple passes over the code to fully
+// simplify the CFG.
+//
+bool CFGSimplifyPass::runOnFunction(Function &F) {
+ SmallPtrSet<BasicBlock*, 16> Reachable;
+ bool Changed = MarkAliveBlocks(F.begin(), Reachable);
+
+ // If there are unreachable blocks in the CFG...
+ if (Reachable.size() != F.size()) {
+ assert(Reachable.size() < F.size());
+ NumSimpl += F.size()-Reachable.size();
+
+ // Loop over all of the basic blocks that are not reachable, dropping all of
+ // their internal references...
+ for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB)
+ if (!Reachable.count(BB)) {
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI!=SE; ++SI)
+ if (Reachable.count(*SI))
+ (*SI)->removePredecessor(BB);
+ BB->dropAllReferences();
+ }
+
+ for (Function::iterator I = ++F.begin(); I != F.end();)
+ if (!Reachable.count(I))
+ I = F.getBasicBlockList().erase(I);
+ else
+ ++I;
+
+ Changed = true;
+ }
+
+ bool LocalChange = true;
+ while (LocalChange) {
+ LocalChange = false;
+
+ // Loop over all of the basic blocks (except the first one) and remove them
+ // if they are unneeded...
+ //
+ for (Function::iterator BBIt = ++F.begin(); BBIt != F.end(); ) {
+ if (SimplifyCFG(BBIt++)) {
+ LocalChange = true;
+ ++NumSimpl;
+ }
+ }
+ Changed |= LocalChange;
+ }
+
+ return Changed;
+}