//===-- 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 family of functions perform various local transformations to the
// program.
//
//===----------------------------------------------------------------------===//
+#include "llvm/Support/MathExtras.h"
#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/iTerminators.h"
-#include "llvm/ConstantHandling.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
+#include "llvm/Intrinsics.h"
+#include <cerrno>
+#include <cmath>
+using namespace llvm;
//===----------------------------------------------------------------------===//
-// Local constant propogation...
+// Local constant propagation...
//
-// ConstantFoldInstruction - If an instruction references constants, try to fold
-// them together...
-//
-bool doConstantPropogation(BasicBlock *BB, BasicBlock::iterator &II) {
- Instruction *Inst = *II;
- if (Constant *C = ConstantFoldInstruction(Inst)) {
+/// 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.
- Inst->replaceAllUsesWith(C);
+ II->replaceAllUsesWith(C);
// Remove the instruction from the basic block...
- delete BB->getInstList().remove(II);
+ 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 ConstantFoldTerminator(BasicBlock *BB, BasicBlock::iterator &II,
- TerminatorInst *T) {
+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
// Set the unconditional destination, and change the insn to be an
// unconditional branch.
BI->setUnconditionalDest(Destination);
- II = BB->end()-1; // Update instruction iterator!
return true;
- }
-#if 0
- // FIXME: TODO: This doesn't work if the destination has PHI nodes with
- // different incoming values on each branch!
- //
- else if (Dest2 == Dest1) { // Conditional branch to same location?
+ } else if (Dest2 == Dest1) { // Conditional branch to same location?
// This branch matches something like this:
// br bool %cond, label %Dest, label %Dest
// and changes it into: br label %Dest
BI->setUnconditionalDest(Dest1);
return true;
}
-#endif
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) {
+ // If we are switching on a constant, we can convert the switch into a
+ // single branch instruction!
+ ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition());
+ BasicBlock *TheOnlyDest = SI->getSuccessor(0); // The default dest
+ BasicBlock *DefaultDest = TheOnlyDest;
+ assert(TheOnlyDest == SI->getDefaultDest() &&
+ "Default destination is not successor #0?");
+
+ // Figure out which case it goes to...
+ for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
+ // Found case matching a constant operand?
+ if (SI->getSuccessorValue(i) == CI) {
+ TheOnlyDest = SI->getSuccessor(i);
+ break;
+ }
+
+ // Check to see if this branch is going to the same place as the default
+ // dest. If so, eliminate it as an explicit compare.
+ if (SI->getSuccessor(i) == DefaultDest) {
+ // Remove this entry...
+ DefaultDest->removePredecessor(SI->getParent());
+ SI->removeCase(i);
+ --i; --e; // Don't skip an entry...
+ continue;
+ }
+
+ // Otherwise, check to see if the switch only branches to one destination.
+ // We do this by reseting "TheOnlyDest" to null when we find two non-equal
+ // destinations.
+ if (SI->getSuccessor(i) != TheOnlyDest) TheOnlyDest = 0;
+ }
+
+ if (CI && !TheOnlyDest) {
+ // Branching on a constant, but not any of the cases, go to the default
+ // successor.
+ TheOnlyDest = SI->getDefaultDest();
+ }
+
+ // If we found a single destination that we can fold the switch into, do so
+ // now.
+ if (TheOnlyDest) {
+ // Insert the new branch..
+ new BranchInst(TheOnlyDest, SI);
+ BasicBlock *BB = SI->getParent();
+
+ // Remove entries from PHI nodes which we no longer branch to...
+ for (unsigned i = 0, e = SI->getNumSuccessors(); i != e; ++i) {
+ // Found case matching a constant operand?
+ BasicBlock *Succ = SI->getSuccessor(i);
+ if (Succ == TheOnlyDest)
+ TheOnlyDest = 0; // Don't modify the first branch to TheOnlyDest
+ else
+ Succ->removePredecessor(BB);
+ }
+
+ // Delete the old switch...
+ BB->getInstList().erase(SI);
+ return true;
+ } 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);
+ // Insert the new branch...
+ new BranchInst(SI->getSuccessor(1), SI->getSuccessor(0), Cond, SI);
+
+ // Delete the old switch...
+ SI->getParent()->getInstList().erase(SI);
+ 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();
+
+ switch (F->getIntrinsicID()) {
+ case Intrinsic::isunordered: return true;
+ default: break;
+ }
+
+ return Name == "sin" || Name == "cos" || Name == "tan" || Name == "sqrt" ||
+ Name == "log" || Name == "log10" || Name == "exp" || Name == "pow" ||
+ Name == "acos" || Name == "asin" || Name == "atan" || Name == "fmod";
+}
+
+static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
+ const Type *Ty) {
+ errno = 0;
+ V = NativeFP(V);
+ if (errno == 0)
+ return ConstantFP::get(Ty, V);
+ return 0;
+}
+
+/// 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 (Operands.size() == 1) {
+ if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
+ double V = Op->getValue();
+ if (Name == "sin")
+ return ConstantFP::get(Ty, sin(V));
+ else if (Name == "cos")
+ return ConstantFP::get(Ty, cos(V));
+ else if (Name == "tan")
+ return ConstantFP::get(Ty, tan(V));
+ else if (Name == "sqrt" && V >= 0)
+ return ConstantFP::get(Ty, sqrt(V));
+ else if (Name == "exp")
+ return ConstantFP::get(Ty, exp(V));
+ else if (Name == "log" && V > 0)
+ return ConstantFP::get(Ty, log(V));
+ else if (Name == "log10")
+ return ConstantFoldFP(log10, V, Ty);
+ else if (Name == "acos")
+ return ConstantFoldFP(acos, V, Ty);
+ else if (Name == "asin")
+ return ConstantFoldFP(asin, V, Ty);
+ else if (Name == "atan")
+ return ConstantFP::get(Ty, atan(V));
+ }
+ } else if (Operands.size() == 2) {
+ if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0]))
+ if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
+ double Op1V = Op1->getValue(), Op2V = Op2->getValue();
+
+ if (Name == "llvm.isunordered")
+ return ConstantBool::get(IsNAN(Op1V) || IsNAN(Op2V));
+ else
+ if (Name == "pow") {
+ errno = 0;
+ double V = pow(Op1V, Op2V);
+ if (errno == 0)
+ return ConstantFP::get(Ty, V);
+ } else if (Name == "fmod") {
+ errno = 0;
+ double V = fmod(Op1V, Op2V);
+ if (errno == 0)
+ return ConstantFP::get(Ty, V);
+ }
+ }
+ }
+ return 0;
+}
+
+
//===----------------------------------------------------------------------===//
// Local dead code elimination...
//
-bool isInstructionTriviallyDead(Instruction *I) {
- return I->use_empty() && !I->hasSideEffects() && !isa<TerminatorInst>(I);
+bool llvm::isInstructionTriviallyDead(Instruction *I) {
+ return I->use_empty() && !I->mayWriteToMemory() && !isa<TerminatorInst>(I);
}
// dceInstruction - Inspect the instruction at *BBI and figure out if it's
// to point to the instruction that immediately succeeded the original
// instruction.
//
-bool dceInstruction(BasicBlock::InstListType &BBIL,
- BasicBlock::iterator &BBI) {
+bool llvm::dceInstruction(BasicBlock::iterator &BBI) {
// Look for un"used" definitions...
- if (isInstructionTriviallyDead(*BBI)) {
- delete BBIL.remove(BBI); // Bye bye
+ if (isInstructionTriviallyDead(BBI)) {
+ BBI = BBI->getParent()->getInstList().erase(BBI); // Bye bye
return true;
}
return false;
}
+
+//===----------------------------------------------------------------------===//
+// PHI Instruction Simplification
+//
+
+/// hasConstantValue - If the specified PHI node always merges together the same
+/// value, return the value, otherwise return null.
+///
+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...
+ !isa<UndefValue>(PN->getIncomingValue(i)))
+ 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 = UndefValue::get(PN->getType());
+
+ // All of the incoming values are the same, return the value now.
+ return InVal;
+}
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