//
// 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.
//
//===----------------------------------------------------------------------===//
//
//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "tailcallelim"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Pass.h"
#include "llvm/Support/CFG.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Compiler.h"
using namespace llvm;
+STATISTIC(NumEliminated, "Number of tail calls removed");
+STATISTIC(NumAccumAdded, "Number of accumulators introduced");
+
namespace {
- Statistic NumEliminated("tailcallelim", "Number of tail calls removed");
- Statistic NumAccumAdded("tailcallelim","Number of accumulators introduced");
+ struct VISIBILITY_HIDDEN TailCallElim : public FunctionPass {
+ static char ID; // Pass identification, replacement for typeid
+ TailCallElim() : FunctionPass((intptr_t)&ID) {}
- struct TailCallElim : public FunctionPass {
virtual bool runOnFunction(Function &F);
private:
bool CanMoveAboveCall(Instruction *I, CallInst *CI);
Value *CanTransformAccumulatorRecursion(Instruction *I, CallInst *CI);
};
+ char TailCallElim::ID = 0;
RegisterPass<TailCallElim> X("tailcallelim", "Tail Call Elimination");
}
// If this alloca is in the body of the function, or if it is a variable
// sized allocation, we cannot tail call eliminate calls marked 'tail'
// with this mechanism.
- if (BB != &BB->getParent()->front() ||
+ if (BB != &BB->getParent()->getEntryBlock() ||
!isa<ConstantInt>(AI->getArraySize()))
CannotTCETailMarkedCall = true;
}
Function *F = TheRI->getParent()->getParent();
Value *ReturnedValue = 0;
+ // TODO: Handle multiple value ret instructions;
+ if (isa<StructType>(F->getReturnType()))
+ return 0;
+
for (Function::iterator BBI = F->begin(), E = F->end(); BBI != E; ++BBI)
if (ReturnInst *RI = dyn_cast<ReturnInst>(BBI->getTerminator()))
if (RI != TheRI) {
"Associative operations should have 2 args!");
// Exactly one operand should be the result of the call instruction...
- if (I->getOperand(0) == CI && I->getOperand(1) == CI ||
- I->getOperand(0) != CI && I->getOperand(1) != CI)
+ if ((I->getOperand(0) == CI && I->getOperand(1) == CI) ||
+ (I->getOperand(0) != CI && I->getOperand(1) != CI))
return 0;
// The only user of this instruction we allow is a single return instruction.
if (&BB->front() == Ret) // Make sure there is something before the ret...
return false;
+
+ // If the return is in the entry block, then making this transformation would
+ // turn infinite recursion into an infinite loop. This transformation is ok
+ // in theory, but breaks some code like:
+ // double fabs(double f) { return __builtin_fabs(f); } // a 'fabs' call
+ // disable this xform in this case, because the code generator will lower the
+ // call to fabs into inline code.
+ if (BB == &F->getEntryBlock())
+ return false;
// Scan backwards from the return, checking to see if there is a tail call in
// this block. If so, set CI to it.
// of the call and return void, ignore the value of the call and return a
// constant, return the value returned by the tail call, or that are being
// accumulator recursion variable eliminated.
- if (Ret->getNumOperands() != 0 && Ret->getReturnValue() != CI &&
+ if (Ret->getNumOperands() == 1 && Ret->getReturnValue() != CI &&
!isa<UndefValue>(Ret->getReturnValue()) &&
AccumulatorRecursionEliminationInitVal == 0 &&
!getCommonReturnValue(Ret, CI))
// create the new entry block, allowing us to branch back to the old entry.
if (OldEntry == 0) {
OldEntry = &F->getEntryBlock();
- std::string OldName = OldEntry->getName(); OldEntry->setName("tailrecurse");
- BasicBlock *NewEntry = new BasicBlock(OldName, F, OldEntry);
- new BranchInst(OldEntry, NewEntry);
+ BasicBlock *NewEntry = BasicBlock::Create("", F, OldEntry);
+ NewEntry->takeName(OldEntry);
+ OldEntry->setName("tailrecurse");
+ BranchInst::Create(OldEntry, NewEntry);
// If this tail call is marked 'tail' and if there are any allocas in the
// entry block, move them up to the new entry block.
Instruction *InsertPos = OldEntry->begin();
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
I != E; ++I) {
- PHINode *PN = new PHINode(I->getType(), I->getName()+".tr", InsertPos);
+ PHINode *PN = PHINode::Create(I->getType(), I->getName()+".tr", InsertPos);
I->replaceAllUsesWith(PN); // Everyone use the PHI node now!
PN->addIncoming(I, NewEntry);
ArgumentPHIs.push_back(PN);
if (AccumulatorRecursionEliminationInitVal) {
Instruction *AccRecInstr = AccumulatorRecursionInstr;
// Start by inserting a new PHI node for the accumulator.
- PHINode *AccPN = new PHINode(AccRecInstr->getType(), "accumulator.tr",
- OldEntry->begin());
+ PHINode *AccPN = PHINode::Create(AccRecInstr->getType(), "accumulator.tr",
+ OldEntry->begin());
// Loop over all of the predecessors of the tail recursion block. For the
// real entry into the function we seed the PHI with the initial value,
// Now that all of the PHI nodes are in place, remove the call and
// ret instructions, replacing them with an unconditional branch.
- new BranchInst(OldEntry, Ret);
+ BranchInst::Create(OldEntry, Ret);
BB->getInstList().erase(Ret); // Remove return.
BB->getInstList().erase(CI); // Remove call.
++NumEliminated;