//===-- Local.cpp - Functions to perform local transformations ------------===//
-//
+//
// 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 family of functions perform various local transformations to the
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
-#include <cerrno>
-#include <cmath>
+#include "llvm/Intrinsics.h"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Support/GetElementPtrTypeIterator.h"
+#include "llvm/Support/MathExtras.h"
using namespace llvm;
//===----------------------------------------------------------------------===//
-// Local constant propagation...
+// Local constant propagation.
//
-/// doConstantPropagation - If an instruction references constants, try to fold
-/// them together...
-///
-bool llvm::doConstantPropagation(BasicBlock::iterator &II) {
- if (Constant *C = ConstantFoldInstruction(II)) {
- // Replaces all of the uses of a variable with uses of the constant.
- II->replaceAllUsesWith(C);
-
- // Remove the instruction from the basic block...
- II = II->getParent()->getInstList().erase(II);
- return true;
- }
-
- return false;
-}
-
-/// ConstantFoldInstruction - Attempt to constant fold the specified
-/// instruction. If successful, the constant result is returned, if not, null
-/// is returned. Note that this function can only fail when attempting to fold
-/// instructions like loads and stores, which have no constant expression form.
-///
-Constant *llvm::ConstantFoldInstruction(Instruction *I) {
- if (PHINode *PN = dyn_cast<PHINode>(I)) {
- if (PN->getNumIncomingValues() == 0)
- return Constant::getNullValue(PN->getType());
-
- Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
- if (Result == 0) return 0;
-
- // Handle PHI nodes specially here...
- for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
- if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
- return 0; // Not all the same incoming constants...
-
- // If we reach here, all incoming values are the same constant.
- return Result;
- } else if (CallInst *CI = dyn_cast<CallInst>(I)) {
- if (Function *F = CI->getCalledFunction())
- if (canConstantFoldCallTo(F)) {
- std::vector<Constant*> Args;
- for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i)
- if (Constant *Op = dyn_cast<Constant>(CI->getOperand(i)))
- Args.push_back(Op);
- else
- return 0;
- return ConstantFoldCall(F, Args);
- }
- return 0;
- }
-
- Constant *Op0 = 0, *Op1 = 0;
- switch (I->getNumOperands()) {
- default:
- case 2:
- Op1 = dyn_cast<Constant>(I->getOperand(1));
- if (Op1 == 0) return 0; // Not a constant?, can't fold
- case 1:
- Op0 = dyn_cast<Constant>(I->getOperand(0));
- if (Op0 == 0) return 0; // Not a constant?, can't fold
- break;
- case 0: return 0;
- }
-
- if (isa<BinaryOperator>(I) || isa<ShiftInst>(I))
- return ConstantExpr::get(I->getOpcode(), Op0, Op1);
-
- switch (I->getOpcode()) {
- default: return 0;
- case Instruction::Cast:
- return ConstantExpr::getCast(Op0, I->getType());
- case Instruction::Select:
- if (Constant *Op2 = dyn_cast<Constant>(I->getOperand(2)))
- return ConstantExpr::getSelect(Op0, Op1, Op2);
- return 0;
- case Instruction::GetElementPtr:
- std::vector<Constant*> IdxList;
- IdxList.reserve(I->getNumOperands()-1);
- if (Op1) IdxList.push_back(Op1);
- for (unsigned i = 2, e = I->getNumOperands(); i != e; ++i)
- if (Constant *C = dyn_cast<Constant>(I->getOperand(i)))
- IdxList.push_back(C);
- else
- return 0; // Non-constant operand
- return ConstantExpr::getGetElementPtr(Op0, IdxList);
- }
-}
-
// ConstantFoldTerminator - If a terminator instruction is predicated on a
// constant value, convert it into an unconditional branch to the constant
// destination.
//
bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
TerminatorInst *T = BB->getTerminator();
-
+
// Branch - See if we are conditional jumping on constant
if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
if (BI->isUnconditional()) return false; // Can't optimize uncond branch
- BasicBlock *Dest1 = cast<BasicBlock>(BI->getOperand(0));
- BasicBlock *Dest2 = cast<BasicBlock>(BI->getOperand(1));
+ BasicBlock *Dest1 = BI->getSuccessor(0);
+ BasicBlock *Dest2 = BI->getSuccessor(1);
- if (ConstantBool *Cond = dyn_cast<ConstantBool>(BI->getCondition())) {
+ if (ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition())) {
// Are we branching on constant?
// YES. Change to unconditional branch...
- BasicBlock *Destination = Cond->getValue() ? Dest1 : Dest2;
- BasicBlock *OldDest = Cond->getValue() ? Dest2 : Dest1;
+ BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2;
+ BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1;
- //cerr << "Function: " << T->getParent()->getParent()
- // << "\nRemoving branch from " << T->getParent()
+ //cerr << "Function: " << T->getParent()->getParent()
+ // << "\nRemoving branch from " << T->getParent()
// << "\n\nTo: " << OldDest << endl;
// Let the basic block know that we are letting go of it. Based on this,
BI->setUnconditionalDest(Destination);
return true;
} else if (Dest2 == Dest1) { // Conditional branch to same location?
- // This branch matches something like this:
+ // This branch matches something like this:
// br bool %cond, label %Dest, label %Dest
// and changes it into: br label %Dest
// now.
if (TheOnlyDest) {
// Insert the new branch..
- new BranchInst(TheOnlyDest, SI);
+ BranchInst::Create(TheOnlyDest, SI);
BasicBlock *BB = SI->getParent();
// Remove entries from PHI nodes which we no longer branch to...
} else if (SI->getNumSuccessors() == 2) {
// Otherwise, we can fold this switch into a conditional branch
// instruction if it has only one non-default destination.
- Value *Cond = new SetCondInst(Instruction::SetEQ, SI->getCondition(),
- SI->getSuccessorValue(1), "cond", SI);
+ Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, SI->getCondition(),
+ SI->getSuccessorValue(1), "cond", SI);
// Insert the new branch...
- new BranchInst(SI->getSuccessor(1), SI->getSuccessor(0), Cond, SI);
+ BranchInst::Create(SI->getSuccessor(1), SI->getSuccessor(0), Cond, SI);
// Delete the old switch...
- SI->getParent()->getInstList().erase(SI);
+ SI->eraseFromParent();
return true;
}
}
return false;
}
-/// canConstantFoldCallTo - Return true if its even possible to fold a call to
-/// the specified function.
-bool llvm::canConstantFoldCallTo(Function *F) {
- const std::string &Name = F->getName();
- return Name == "sin" || Name == "cos" || Name == "tan" || Name == "sqrt" ||
- Name == "log" || Name == "log10" || Name == "exp" || Name == "pow";
-}
-
-/// ConstantFoldCall - Attempt to constant fold a call to the specified function
-/// with the specified arguments, returning null if unsuccessful.
-Constant *llvm::ConstantFoldCall(Function *F,
- const std::vector<Constant*> &Operands) {
- const std::string &Name = F->getName();
- const Type *Ty = F->getReturnType();
-
- if (Name == "sin") {
- if (Operands.size() == 1)
- if (ConstantFP *CFP = dyn_cast<ConstantFP>(Operands[0]))
- return ConstantFP::get(Ty, sin(CFP->getValue()));
-
- } else if (Name == "cos") {
- if (Operands.size() == 1)
- if (ConstantFP *CFP = dyn_cast<ConstantFP>(Operands[0]))
- return ConstantFP::get(Ty, cos(CFP->getValue()));
-
- } else if (Name == "tan") {
- if (Operands.size() == 1)
- if (ConstantFP *CFP = dyn_cast<ConstantFP>(Operands[0]))
- return ConstantFP::get(Ty, tan(CFP->getValue()));
-
- } else if (Name == "sqrt") {
- if (Operands.size() == 1)
- if (ConstantFP *CFP = dyn_cast<ConstantFP>(Operands[0]))
- if (CFP->getValue() >= 0)
- return ConstantFP::get(Ty, sqrt(CFP->getValue()));
- } else if (Name == "exp") {
- if (Operands.size() == 1)
- if (ConstantFP *CFP = dyn_cast<ConstantFP>(Operands[0]))
- return ConstantFP::get(Ty, exp(CFP->getValue()));
- } else if (Name == "log") {
- if (Operands.size() == 1)
- if (ConstantFP *CFP = dyn_cast<ConstantFP>(Operands[0]))
- if (CFP->getValue() > 0)
- return ConstantFP::get(Ty, log(CFP->getValue()));
- } else if (Name == "log10") {
- if (Operands.size() == 1)
- if (ConstantFP *CFP = dyn_cast<ConstantFP>(Operands[0]))
- if (CFP->getValue() > 0)
- return ConstantFP::get(Ty, log10(CFP->getValue()));
- } else if (Name == "pow") {
- if (Operands.size() == 2)
- if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0]))
- if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
- errno = 0;
- double V = pow(Op1->getValue(), Op2->getValue());
- if (errno == 0)
- return ConstantFP::get(Ty, V);
- }
- }
- return 0;
-}
-
-
-
//===----------------------------------------------------------------------===//
// Local dead code elimination...
//
+/// isInstructionTriviallyDead - Return true if the result produced by the
+/// instruction is not used, and the instruction has no side effects.
+///
bool llvm::isInstructionTriviallyDead(Instruction *I) {
- return I->use_empty() && !I->mayWriteToMemory() && !isa<TerminatorInst>(I);
-}
+ if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
-// dceInstruction - Inspect the instruction at *BBI and figure out if it's
-// [trivially] dead. If so, remove the instruction and update the iterator
-// to point to the instruction that immediately succeeded the original
-// instruction.
-//
-bool llvm::dceInstruction(BasicBlock::iterator &BBI) {
- // Look for un"used" definitions...
- if (isInstructionTriviallyDead(BBI)) {
- BBI = BBI->getParent()->getInstList().erase(BBI); // Bye bye
+ if (!I->mayWriteToMemory())
return true;
- }
+
+ // Special case intrinsics that "may write to memory" but can be deleted when
+ // dead.
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
+ // Safe to delete llvm.stacksave if dead.
+ if (II->getIntrinsicID() == Intrinsic::stacksave)
+ return true;
+
return false;
}
+/// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
+/// trivially dead instruction, delete it. If that makes any of its operands
+/// trivially dead, delete them too, recursively.
+///
+/// If DeadInst is specified, the vector is filled with the instructions that
+/// are actually deleted.
+void llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V,
+ SmallVectorImpl<Instruction*> *DeadInst) {
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (!I || !I->use_empty() || !isInstructionTriviallyDead(I))
+ return;
+
+ SmallVector<Instruction*, 16> DeadInsts;
+ DeadInsts.push_back(I);
+
+ while (!DeadInsts.empty()) {
+ I = DeadInsts.back();
+ DeadInsts.pop_back();
+
+ // If the client wanted to know, tell it about deleted instructions.
+ if (DeadInst)
+ DeadInst->push_back(I);
+
+ // Null out all of the instruction's operands to see if any operand becomes
+ // dead as we go.
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
+ Value *OpV = I->getOperand(i);
+ I->setOperand(i, 0);
+
+ if (!OpV->use_empty()) continue;
+
+ // If the operand is an instruction that became dead as we nulled out the
+ // operand, and if it is 'trivially' dead, delete it in a future loop
+ // iteration.
+ if (Instruction *OpI = dyn_cast<Instruction>(OpV))
+ if (isInstructionTriviallyDead(OpI))
+ DeadInsts.push_back(OpI);
+ }
+
+ I->eraseFromParent();
+ }
+}
+
+
//===----------------------------------------------------------------------===//
-// PHI Instruction Simplification
+// Control Flow Graph Restructuring...
//
-/// hasConstantValue - If the specified PHI node always merges together the same
-/// value, return the value, otherwise return null.
+/// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
+/// predecessor is known to have one successor (DestBB!). Eliminate the edge
+/// between them, moving the instructions in the predecessor into DestBB and
+/// deleting the predecessor block.
///
-Value *llvm::hasConstantValue(PHINode *PN) {
- // If the PHI node only has one incoming value, eliminate the PHI node...
- if (PN->getNumIncomingValues() == 1)
- return PN->getIncomingValue(0);
-
- // Otherwise if all of the incoming values are the same for the PHI, replace
- // the PHI node with the incoming value.
- //
- Value *InVal = 0;
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
- if (PN->getIncomingValue(i) != PN) // Not the PHI node itself...
- if (InVal && PN->getIncomingValue(i) != InVal)
- return 0; // Not the same, bail out.
- else
- InVal = PN->getIncomingValue(i);
-
- // The only case that could cause InVal to be null is if we have a PHI node
- // that only has entries for itself. In this case, there is no entry into the
- // loop, so kill the PHI.
- //
- if (InVal == 0) InVal = Constant::getNullValue(PN->getType());
+void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB) {
+ // If BB has single-entry PHI nodes, fold them.
+ while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
+ Value *NewVal = PN->getIncomingValue(0);
+ // Replace self referencing PHI with undef, it must be dead.
+ if (NewVal == PN) NewVal = UndefValue::get(PN->getType());
+ PN->replaceAllUsesWith(NewVal);
+ PN->eraseFromParent();
+ }
+
+ BasicBlock *PredBB = DestBB->getSinglePredecessor();
+ assert(PredBB && "Block doesn't have a single predecessor!");
+
+ // Splice all the instructions from PredBB to DestBB.
+ PredBB->getTerminator()->eraseFromParent();
+ DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
+
+ // Anything that branched to PredBB now branches to DestBB.
+ PredBB->replaceAllUsesWith(DestBB);
+
+ // Nuke BB.
+ PredBB->eraseFromParent();
+}
- // All of the incoming values are the same, return the value now.
- return InVal;
+/// OnlyUsedByDbgIntrinsics - Return true if the instruction I is only used
+/// by DbgIntrinsics. If DbgInUses is specified then the vector is filled
+/// with the DbgInfoIntrinsic that use the instruction I.
+bool llvm::OnlyUsedByDbgInfoIntrinsics(Instruction *I,
+ SmallVectorImpl<DbgInfoIntrinsic *> *DbgInUses) {
+ if (DbgInUses)
+ DbgInUses->clear();
+
+ for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE;
+ ++UI) {
+ if (DbgInfoIntrinsic *DI = dyn_cast<DbgInfoIntrinsic>(*UI)) {
+ if (DbgInUses)
+ DbgInUses->push_back(DI);
+ } else {
+ if (DbgInUses)
+ DbgInUses->clear();
+ return false;
+ }
+ }
+ return true;
}
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