//
// 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 is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a simple interprocedural pass which walks the
// call-graph, turning invoke instructions into calls, iff the callee cannot
-// throw an exception. It implements this as a bottom-up traversal of the
-// call-graph.
+// throw an exception, and marking functions 'nounwind' if they cannot throw.
+// It implements this as a bottom-up traversal of the call-graph.
//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "prune-eh"
#include "llvm/Transforms/IPO.h"
#include "llvm/CallGraphSCCPass.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
-#include "llvm/Intrinsics.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/CallGraph.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Support/Compiler.h"
#include <set>
#include <algorithm>
using namespace llvm;
-namespace {
- Statistic NumRemoved("prune-eh", "Number of invokes removed");
- Statistic NumUnreach("prune-eh", "Number of noreturn calls optimized");
-
- struct PruneEH : public CallGraphSCCPass {
- /// DoesNotUnwind - This set contains all of the functions which we have
- /// determined cannot unwind.
- std::set<CallGraphNode*> DoesNotUnwind;
+STATISTIC(NumRemoved, "Number of invokes removed");
+STATISTIC(NumUnreach, "Number of noreturn calls optimized");
- /// DoesNotReturn - This set contains all of the functions which we have
- /// determined cannot return normally (but might unwind).
- std::set<CallGraphNode*> DoesNotReturn;
+namespace {
+ struct VISIBILITY_HIDDEN PruneEH : public CallGraphSCCPass {
+ static char ID; // Pass identification, replacement for typeid
+ PruneEH() : CallGraphSCCPass((intptr_t)&ID) {}
// runOnSCC - Analyze the SCC, performing the transformation if possible.
bool runOnSCC(const std::vector<CallGraphNode *> &SCC);
bool SimplifyFunction(Function *F);
void DeleteBasicBlock(BasicBlock *BB);
};
+
+ char PruneEH::ID = 0;
RegisterPass<PruneEH> X("prune-eh", "Remove unused exception handling info");
}
-ModulePass *llvm::createPruneEHPass() { return new PruneEH(); }
+Pass *llvm::createPruneEHPass() { return new PruneEH(); }
bool PruneEH::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
for (unsigned i = 0, e = SCC.size();
(!SCCMightUnwind || !SCCMightReturn) && i != e; ++i) {
Function *F = SCC[i]->getFunction();
- if (F == 0 || (F->isExternal() && !F->getIntrinsicID())) {
+ if (F == 0) {
SCCMightUnwind = true;
SCCMightReturn = true;
+ } else if (F->isDeclaration()) {
+ SCCMightUnwind |= !F->doesNotThrow();
+ SCCMightReturn |= !F->doesNotReturn();
} else {
- if (F->isExternal())
- SCCMightReturn = true;
+ bool CheckUnwind = !SCCMightUnwind && !F->doesNotThrow();
+ bool CheckReturn = !SCCMightReturn && !F->doesNotReturn();
+
+ if (!CheckUnwind && !CheckReturn)
+ continue;
// Check to see if this function performs an unwind or calls an
// unwinding function.
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
- if (isa<UnwindInst>(BB->getTerminator())) { // Uses unwind!
+ if (CheckUnwind && isa<UnwindInst>(BB->getTerminator())) {
+ // Uses unwind!
SCCMightUnwind = true;
- } else if (isa<ReturnInst>(BB->getTerminator())) {
+ } else if (CheckReturn && isa<ReturnInst>(BB->getTerminator())) {
SCCMightReturn = true;
}
// Invoke instructions don't allow unwinding to continue, so we are
// only interested in call instructions.
- if (!SCCMightUnwind)
+ if (CheckUnwind && !SCCMightUnwind)
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
if (CallInst *CI = dyn_cast<CallInst>(I)) {
- if (Function *Callee = CI->getCalledFunction()) {
+ if (CI->doesNotThrow()) {
+ // This call cannot throw.
+ } else if (Function *Callee = CI->getCalledFunction()) {
CallGraphNode *CalleeNode = CG[Callee];
- // If the callee is outside our current SCC, or if it is not
- // known to throw, then we might throw also.
- if (std::find(SCC.begin(), SCC.end(), CalleeNode) == SCC.end()&&
- !DoesNotUnwind.count(CalleeNode)) {
+ // If the callee is outside our current SCC then we may
+ // throw because it might.
+ if (std::find(SCC.begin(), SCC.end(), CalleeNode) == SCC.end()){
SCCMightUnwind = true;
break;
}
}
// If the SCC doesn't unwind or doesn't throw, note this fact.
- if (!SCCMightUnwind)
- for (unsigned i = 0, e = SCC.size(); i != e; ++i)
- DoesNotUnwind.insert(SCC[i]);
- if (!SCCMightReturn)
- for (unsigned i = 0, e = SCC.size(); i != e; ++i)
- DoesNotReturn.insert(SCC[i]);
+ if (!SCCMightUnwind || !SCCMightReturn)
+ for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
+ ParameterAttributes NewAttributes = ParamAttr::None;
+
+ if (!SCCMightUnwind)
+ NewAttributes |= ParamAttr::NoUnwind;
+ if (!SCCMightReturn)
+ NewAttributes |= ParamAttr::NoReturn;
+
+ const PAListPtr &PAL = SCC[i]->getFunction()->getParamAttrs();
+ SCC[i]->getFunction()->setParamAttrs(PAL.addAttr(0, NewAttributes));
+ }
for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
// Convert any invoke instructions to non-throwing functions in this node
// function if we have invokes to non-unwinding functions or code after calls to
// no-return functions.
bool PruneEH::SimplifyFunction(Function *F) {
- CallGraph &CG = getAnalysis<CallGraph>();
bool MadeChange = false;
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
- if (Function *F = II->getCalledFunction())
- if (DoesNotUnwind.count(CG[F])) {
- // Insert a call instruction before the invoke...
- std::string Name = II->getName(); II->setName("");
- CallInst *Call = new CallInst(II->getCalledValue(),
- std::vector<Value*>(II->op_begin()+3,
- II->op_end()),
- Name, II);
- Call->setCallingConv(II->getCallingConv());
-
- // Anything that used the value produced by the invoke instruction
- // now uses the value produced by the call instruction.
- II->replaceAllUsesWith(Call);
- BasicBlock *UnwindBlock = II->getUnwindDest();
- UnwindBlock->removePredecessor(II->getParent());
-
- // Insert a branch to the normal destination right before the
- // invoke.
- new BranchInst(II->getNormalDest(), II);
-
- // Finally, delete the invoke instruction!
- BB->getInstList().pop_back();
-
- // If the unwind block is now dead, nuke it.
- if (pred_begin(UnwindBlock) == pred_end(UnwindBlock))
- DeleteBasicBlock(UnwindBlock); // Delete the new BB.
-
- ++NumRemoved;
- MadeChange = true;
- }
+ if (II->doesNotThrow()) {
+ SmallVector<Value*, 8> Args(II->op_begin()+3, II->op_end());
+ // Insert a call instruction before the invoke.
+ CallInst *Call = CallInst::Create(II->getCalledValue(),
+ Args.begin(), Args.end(), "", II);
+ Call->takeName(II);
+ Call->setCallingConv(II->getCallingConv());
+ Call->setParamAttrs(II->getParamAttrs());
+
+ // Anything that used the value produced by the invoke instruction
+ // now uses the value produced by the call instruction.
+ II->replaceAllUsesWith(Call);
+ BasicBlock *UnwindBlock = II->getUnwindDest();
+ UnwindBlock->removePredecessor(II->getParent());
+
+ // Insert a branch to the normal destination right before the
+ // invoke.
+ BranchInst::Create(II->getNormalDest(), II);
+
+ // Finally, delete the invoke instruction!
+ BB->getInstList().pop_back();
+
+ // If the unwind block is now dead, nuke it.
+ if (pred_begin(UnwindBlock) == pred_end(UnwindBlock))
+ DeleteBasicBlock(UnwindBlock); // Delete the new BB.
+
+ ++NumRemoved;
+ MadeChange = true;
+ }
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; )
if (CallInst *CI = dyn_cast<CallInst>(I++))
- if (Function *Callee = CI->getCalledFunction())
- if (DoesNotReturn.count(CG[Callee]) && !isa<UnreachableInst>(I)) {
- // This call calls a function that cannot return. Insert an
- // unreachable instruction after it and simplify the code. Do this
- // by splitting the BB, adding the unreachable, then deleting the
- // new BB.
- BasicBlock *New = BB->splitBasicBlock(I);
-
- // Remove the uncond branch and add an unreachable.
- BB->getInstList().pop_back();
- new UnreachableInst(BB);
-
- DeleteBasicBlock(New); // Delete the new BB.
- MadeChange = true;
- ++NumUnreach;
- break;
- }
+ if (CI->doesNotReturn() && !isa<UnreachableInst>(I)) {
+ // This call calls a function that cannot return. Insert an
+ // unreachable instruction after it and simplify the code. Do this
+ // by splitting the BB, adding the unreachable, then deleting the
+ // new BB.
+ BasicBlock *New = BB->splitBasicBlock(I);
+
+ // Remove the uncond branch and add an unreachable.
+ BB->getInstList().pop_back();
+ new UnreachableInst(BB);
+ DeleteBasicBlock(New); // Delete the new BB.
+ MadeChange = true;
+ ++NumUnreach;
+ break;
+ }
}
+
return MadeChange;
}
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