#define DEBUG_TYPE "tailcallelim"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
-#include "llvm/IntrinsicInst.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/CaptureTracking.h"
#include "llvm/Analysis/InlineCost.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/CFG.h"
-#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/STLExtras.h"
using namespace llvm;
STATISTIC(NumEliminated, "Number of tail calls removed");
virtual bool runOnFunction(Function &F);
private:
- CallInst *FindTRECandidate(Instruction *I,
- bool CannotTailCallElimCallsMarkedTail);
- bool EliminateRecursiveTailCall(CallInst *CI, ReturnInst *Ret,
- BasicBlock *&OldEntry,
- bool &TailCallsAreMarkedTail,
- SmallVector<PHINode*, 8> &ArgumentPHIs,
- bool CannotTailCallElimCallsMarkedTail);
- bool FoldReturnAndProcessPred(BasicBlock *BB,
- ReturnInst *Ret, BasicBlock *&OldEntry,
- bool &TailCallsAreMarkedTail,
- SmallVector<PHINode*, 8> &ArgumentPHIs,
- bool CannotTailCallElimCallsMarkedTail);
bool ProcessReturningBlock(ReturnInst *RI, BasicBlock *&OldEntry,
bool &TailCallsAreMarkedTail,
SmallVector<PHINode*, 8> &ArgumentPHIs,
bool TailCallsAreMarkedTail = false;
SmallVector<PHINode*, 8> ArgumentPHIs;
bool MadeChange = false;
+
bool FunctionContainsEscapingAllocas = false;
// CannotTCETailMarkedCall - If true, we cannot perform TCE on tail calls
return false;
// Second pass, change any tail calls to loops.
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
- if (ReturnInst *Ret = dyn_cast<ReturnInst>(BB->getTerminator())) {
- bool Change = ProcessReturningBlock(Ret, OldEntry, TailCallsAreMarkedTail,
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+ if (ReturnInst *Ret = dyn_cast<ReturnInst>(BB->getTerminator()))
+ MadeChange |= ProcessReturningBlock(Ret, OldEntry, TailCallsAreMarkedTail,
ArgumentPHIs,CannotTCETailMarkedCall);
- if (!Change && BB->getFirstNonPHIOrDbg() == Ret)
- Change = FoldReturnAndProcessPred(BB, Ret, OldEntry,
- TailCallsAreMarkedTail, ArgumentPHIs,
- CannotTCETailMarkedCall);
- MadeChange |= Change;
- }
- }
// If we eliminated any tail recursions, it's possible that we inserted some
// silly PHI nodes which just merge an initial value (the incoming operand)
return getCommonReturnValue(cast<ReturnInst>(I->use_back()), CI);
}
-static Instruction *FirstNonDbg(BasicBlock::iterator I) {
- while (isa<DbgInfoIntrinsic>(I))
- ++I;
- return &*I;
-}
-
-CallInst*
-TailCallElim::FindTRECandidate(Instruction *TI,
- bool CannotTailCallElimCallsMarkedTail) {
- BasicBlock *BB = TI->getParent();
+bool TailCallElim::ProcessReturningBlock(ReturnInst *Ret, BasicBlock *&OldEntry,
+ bool &TailCallsAreMarkedTail,
+ SmallVector<PHINode*, 8> &ArgumentPHIs,
+ bool CannotTailCallElimCallsMarkedTail) {
+ BasicBlock *BB = Ret->getParent();
Function *F = BB->getParent();
- if (&BB->front() == TI) // Make sure there is something before the terminator.
- return 0;
+ if (&BB->front() == Ret) // Make sure there is something before the ret...
+ 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.
- CallInst *CI = 0;
- BasicBlock::iterator BBI = TI;
- while (true) {
+ CallInst *CI;
+ BasicBlock::iterator BBI = Ret;
+ while (1) {
CI = dyn_cast<CallInst>(BBI);
if (CI && CI->getCalledFunction() == F)
break;
if (BBI == BB->begin())
- return 0; // Didn't find a potential tail call.
+ return false; // Didn't find a potential tail call.
--BBI;
}
// If this call is marked as a tail call, and if there are dynamic allocas in
// the function, we cannot perform this optimization.
if (CI->isTailCall() && CannotTailCallElimCallsMarkedTail)
- return 0;
+ return false;
// As a special case, detect code like this:
// double fabs(double f) { return __builtin_fabs(f); } // a 'fabs' call
// and disable this xform in this case, because the code generator will
// lower the call to fabs into inline code.
if (BB == &F->getEntryBlock() &&
- FirstNonDbg(BB->front()) == CI &&
- FirstNonDbg(llvm::next(BB->begin())) == TI &&
+ &BB->front() == CI && &*++BB->begin() == Ret &&
callIsSmall(F)) {
// A single-block function with just a call and a return. Check that
// the arguments match.
for (; I != E && FI != FE; ++I, ++FI)
if (*I != &*FI) break;
if (I == E && FI == FE)
- return 0;
+ return false;
}
- return CI;
-}
-
-bool TailCallElim::EliminateRecursiveTailCall(CallInst *CI, ReturnInst *Ret,
- BasicBlock *&OldEntry,
- bool &TailCallsAreMarkedTail,
- SmallVector<PHINode*, 8> &ArgumentPHIs,
- bool CannotTailCallElimCallsMarkedTail) {
// If we are introducing accumulator recursion to eliminate operations after
// the call instruction that are both associative and commutative, the initial
// value for the accumulator is placed in this variable. If this value is set
// tail call if all of the instructions between the call and the return are
// movable to above the call itself, leaving the call next to the return.
// Check that this is the case now.
- BasicBlock::iterator BBI = CI;
- for (++BBI; &*BBI != Ret; ++BBI) {
+ for (BBI = CI, ++BBI; &*BBI != Ret; ++BBI) {
if (CanMoveAboveCall(BBI, CI)) continue;
// If we can't move the instruction above the call, it might be because it
return false;
}
- BasicBlock *BB = Ret->getParent();
- Function *F = BB->getParent();
-
// OK! We can transform this tail call. If this is the first one found,
// create the new entry block, allowing us to branch back to the old entry.
if (OldEntry == 0) {
++NumEliminated;
return true;
}
-
-bool TailCallElim::FoldReturnAndProcessPred(BasicBlock *BB,
- ReturnInst *Ret, BasicBlock *&OldEntry,
- bool &TailCallsAreMarkedTail,
- SmallVector<PHINode*, 8> &ArgumentPHIs,
- bool CannotTailCallElimCallsMarkedTail) {
- bool Change = false;
-
- // If the return block contains nothing but the return and PHI's,
- // there might be an opportunity to duplicate the return in its
- // predecessors and perform TRC there. Look for predecessors that end
- // in unconditional branch and recursive call(s).
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB);
- PI != E; ++PI) {
- BasicBlock *Pred = *PI;
- TerminatorInst *PTI = Pred->getTerminator();
- if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) {
- CallInst *CI = 0;
- if (BI->isUnconditional() &&
- (CI = FindTRECandidate(BI, CannotTailCallElimCallsMarkedTail))) {
- DEBUG(dbgs() << "FOLDING: " << *BB
- << "INTO UNCOND BRANCH PRED: " << *Pred);
- EliminateRecursiveTailCall(CI,
- FoldReturnIntoUncondBranch(Ret, BB, Pred),
- OldEntry, TailCallsAreMarkedTail, ArgumentPHIs,
- CannotTailCallElimCallsMarkedTail);
- Change = true;
- }
- }
- }
-
- return Change;
-}
-
-bool TailCallElim::ProcessReturningBlock(ReturnInst *Ret, BasicBlock *&OldEntry,
- bool &TailCallsAreMarkedTail,
- SmallVector<PHINode*, 8> &ArgumentPHIs,
- bool CannotTailCallElimCallsMarkedTail) {
- CallInst *CI = FindTRECandidate(Ret, CannotTailCallElimCallsMarkedTail);
- if (!CI)
- return false;
-
- return EliminateRecursiveTailCall(CI, Ret, OldEntry, TailCallsAreMarkedTail,
- ArgumentPHIs,
- CannotTailCallElimCallsMarkedTail);
-}
projects / oota-llvm.git / blobdiff