[llvm-commits] [llvm] r51130 - in /llvm/trunk/lib/Transforms/Scalar: SimplifyCFG.cpp SimplifyCFGPass.cpp
Chris Lattner
sabre at nondot.org
Wed May 14 13:38:44 PDT 2008
Author: lattner
Date: Wed May 14 15:38:44 2008
New Revision: 51130
URL: http://llvm.org/viewvc/llvm-project?rev=51130&view=rev
Log:
rename SimplifyCFG.cpp -> SimplifyCFGPass.cpp
Added:
llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp
- copied, changed from r51108, llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp
Removed:
llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp
Removed: llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp?rev=51129&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp (removed)
@@ -1,231 +0,0 @@
-//===- SimplifyCFG.cpp - CFG Simplification Pass --------------------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file 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, along
-// with a collection of other peephole control flow optimizations. For example:
-//
-// * 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.
-// * Changes invoke instructions to nounwind functions to be calls.
-// * Change things like "if (x) if (y)" into "if (x&y)".
-// * etc..
-//
-//===----------------------------------------------------------------------===//
-
-#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/ParameterAttributes.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/Compiler.h"
-#include "llvm/Pass.h"
-#include "llvm/ADT/SmallVector.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;
-static RegisterPass<CFGSimplifyPass> X("simplifycfg", "Simplify the CFG");
-
-// Public interface to the CFGSimplification pass
-FunctionPass *llvm::createCFGSimplificationPass() {
- return new CFGSimplifyPass();
-}
-
-/// ChangeToUnreachable - Insert an unreachable instruction before the specified
-/// instruction, making it and the rest of the code in the block dead.
-static void ChangeToUnreachable(Instruction *I) {
- BasicBlock *BB = I->getParent();
- // Loop over all of the successors, removing BB's entry from any PHI
- // nodes.
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
- (*SI)->removePredecessor(BB);
-
- new UnreachableInst(I);
-
- // All instructions after this are dead.
- BasicBlock::iterator BBI = I, BBE = BB->end();
- while (BBI != BBE) {
- if (!BBI->use_empty())
- BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
- BB->getInstList().erase(BBI++);
- }
-}
-
-/// ChangeToCall - Convert the specified invoke into a normal call.
-static void ChangeToCall(InvokeInst *II) {
- BasicBlock *BB = II->getParent();
- SmallVector<Value*, 8> Args(II->op_begin()+3, II->op_end());
- CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args.begin(),
- Args.end(), "", II);
- NewCall->takeName(II);
- NewCall->setCallingConv(II->getCallingConv());
- NewCall->setParamAttrs(II->getParamAttrs());
- II->replaceAllUsesWith(NewCall);
-
- // Follow the call by a branch to the normal destination.
- BranchInst::Create(II->getNormalDest(), II);
-
- // Update PHI nodes in the unwind destination
- II->getUnwindDest()->removePredecessor(BB);
- BB->getInstList().erase(II);
-}
-
-static bool MarkAliveBlocks(BasicBlock *BB,
- SmallPtrSet<BasicBlock*, 128> &Reachable) {
-
- SmallVector<BasicBlock*, 128> 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
- // canonicalizes unreachable insts into stores to null or undef.
- for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
- if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
- if (CI->doesNotReturn()) {
- // If we found a call to a no-return function, insert an unreachable
- // instruction after it. Make sure there isn't *already* one there
- // though.
- ++BBI;
- if (!isa<UnreachableInst>(BBI)) {
- ChangeToUnreachable(BBI);
- Changed = true;
- }
- break;
- }
- }
-
- if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
- if (isa<ConstantPointerNull>(SI->getOperand(1)) ||
- isa<UndefValue>(SI->getOperand(1))) {
- ChangeToUnreachable(SI);
- Changed = true;
- break;
- }
- }
-
- // Turn invokes that call 'nounwind' functions into ordinary calls.
- if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
- if (II->doesNotThrow()) {
- ChangeToCall(II);
- Changed = true;
- }
-
- Changed |= ConstantFoldTerminator(BB);
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
- Worklist.push_back(*SI);
- }
- return Changed;
-}
-
-/// RemoveUnreachableBlocks - Remove blocks that are not reachable, even if they
-/// are in a dead cycle. Return true if a change was made, false otherwise.
-static bool RemoveUnreachableBlocks(Function &F) {
- SmallPtrSet<BasicBlock*, 128> Reachable;
- bool Changed = MarkAliveBlocks(F.begin(), Reachable);
-
- // If there are unreachable blocks in the CFG...
- if (Reachable.size() == F.size())
- return Changed;
-
- 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))
- continue;
-
- 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;
-
- return true;
-}
-
-/// IterativeSimplifyCFG - Call SimplifyCFG on all the blocks in the function,
-/// iterating until no more changes are made.
-static bool IterativeSimplifyCFG(Function &F) {
- bool Changed = false;
- 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;
-}
-
-// It is possible that we may require multiple passes over the code to fully
-// simplify the CFG.
-//
-bool CFGSimplifyPass::runOnFunction(Function &F) {
- bool EverChanged = RemoveUnreachableBlocks(F);
- EverChanged |= IterativeSimplifyCFG(F);
-
- // If neither pass changed anything, we're done.
- if (!EverChanged) return false;
-
- // IterativeSimplifyCFG can (rarely) make some loops dead. If this happens,
- // RemoveUnreachableBlocks is needed to nuke them, which means we should
- // iterate between the two optimizations. We structure the code like this to
- // avoid reruning IterativeSimplifyCFG if the second pass of
- // RemoveUnreachableBlocks doesn't do anything.
- if (!RemoveUnreachableBlocks(F))
- return true;
-
- do {
- EverChanged = IterativeSimplifyCFG(F);
- EverChanged |= RemoveUnreachableBlocks(F);
- } while (EverChanged);
-
- return true;
-}
Copied: llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp (from r51108, llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp)
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp?p2=llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp&p1=llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp&r1=51108&r2=51130&rev=51130&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp Wed May 14 15:38:44 2008
@@ -1,4 +1,4 @@
-//===- SimplifyCFG.cpp - CFG Simplification Pass --------------------------===//
+//===- SimplifyCFGPass.cpp - CFG Simplification Pass ----------------------===//
//
// The LLVM Compiler Infrastructure
//
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