//===----------------------------------------------------------------------===//
//
// This file implements routines for folding instructions into simpler forms
-// that do not require creating new instructions. For example, this does
-// constant folding, and can handle identities like (X&0)->0.
+// that do not require creating new instructions. This does constant folding
+// ("add i32 1, 1" -> "2") but can also handle non-constant operands, either
+// returning a constant ("and i32 %x, 0" -> "0") or an already existing value
+// ("and i32 %x, %x" -> "%x").
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/ConstantFolding.h"
-#include "llvm/Support/ValueHandle.h"
-#include "llvm/Instructions.h"
+#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/PatternMatch.h"
+#include "llvm/Support/ValueHandle.h"
+#include "llvm/Target/TargetData.h"
using namespace llvm;
using namespace llvm::PatternMatch;
+#define RecursionLimit 3
+
+static Value *SimplifyBinOp(unsigned, Value *, Value *, const TargetData *,
+ const DominatorTree *, unsigned);
+static Value *SimplifyCmpInst(unsigned, Value *, Value *, const TargetData *,
+ const DominatorTree *, unsigned);
+
+/// ValueDominatesPHI - Does the given value dominate the specified phi node?
+static bool ValueDominatesPHI(Value *V, PHINode *P, const DominatorTree *DT) {
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (!I)
+ // Arguments and constants dominate all instructions.
+ return true;
+
+ // If we have a DominatorTree then do a precise test.
+ if (DT)
+ return DT->dominates(I, P);
+
+ // Otherwise, if the instruction is in the entry block, and is not an invoke,
+ // then it obviously dominates all phi nodes.
+ if (I->getParent() == &I->getParent()->getParent()->getEntryBlock() &&
+ !isa<InvokeInst>(I))
+ return true;
+
+ return false;
+}
+
+/// ThreadBinOpOverSelect - In the case of a binary operation with a select
+/// instruction as an operand, try to simplify the binop by seeing whether
+/// evaluating it on both branches of the select results in the same value.
+/// Returns the common value if so, otherwise returns null.
+static Value *ThreadBinOpOverSelect(unsigned Opcode, Value *LHS, Value *RHS,
+ const TargetData *TD,
+ const DominatorTree *DT,
+ unsigned MaxRecurse) {
+ SelectInst *SI;
+ if (isa<SelectInst>(LHS)) {
+ SI = cast<SelectInst>(LHS);
+ } else {
+ assert(isa<SelectInst>(RHS) && "No select instruction operand!");
+ SI = cast<SelectInst>(RHS);
+ }
+
+ // Evaluate the BinOp on the true and false branches of the select.
+ Value *TV;
+ Value *FV;
+ if (SI == LHS) {
+ TV = SimplifyBinOp(Opcode, SI->getTrueValue(), RHS, TD, DT, MaxRecurse);
+ FV = SimplifyBinOp(Opcode, SI->getFalseValue(), RHS, TD, DT, MaxRecurse);
+ } else {
+ TV = SimplifyBinOp(Opcode, LHS, SI->getTrueValue(), TD, DT, MaxRecurse);
+ FV = SimplifyBinOp(Opcode, LHS, SI->getFalseValue(), TD, DT, MaxRecurse);
+ }
+
+ // If they simplified to the same value, then return the common value.
+ // If they both failed to simplify then return null.
+ if (TV == FV)
+ return TV;
+
+ // If one branch simplified to undef, return the other one.
+ if (TV && isa<UndefValue>(TV))
+ return FV;
+ if (FV && isa<UndefValue>(FV))
+ return TV;
+
+ // If applying the operation did not change the true and false select values,
+ // then the result of the binop is the select itself.
+ if (TV == SI->getTrueValue() && FV == SI->getFalseValue())
+ return SI;
+
+ // If one branch simplified and the other did not, and the simplified
+ // value is equal to the unsimplified one, return the simplified value.
+ // For example, select (cond, X, X & Z) & Z -> X & Z.
+ if ((FV && !TV) || (TV && !FV)) {
+ // Check that the simplified value has the form "X op Y" where "op" is the
+ // same as the original operation.
+ Instruction *Simplified = dyn_cast<Instruction>(FV ? FV : TV);
+ if (Simplified && Simplified->getOpcode() == Opcode) {
+ // The value that didn't simplify is "UnsimplifiedLHS op UnsimplifiedRHS".
+ // We already know that "op" is the same as for the simplified value. See
+ // if the operands match too. If so, return the simplified value.
+ Value *UnsimplifiedBranch = FV ? SI->getTrueValue() : SI->getFalseValue();
+ Value *UnsimplifiedLHS = SI == LHS ? UnsimplifiedBranch : LHS;
+ Value *UnsimplifiedRHS = SI == LHS ? RHS : UnsimplifiedBranch;
+ if (Simplified->getOperand(0) == UnsimplifiedLHS &&
+ Simplified->getOperand(1) == UnsimplifiedRHS)
+ return Simplified;
+ if (Simplified->isCommutative() &&
+ Simplified->getOperand(1) == UnsimplifiedLHS &&
+ Simplified->getOperand(0) == UnsimplifiedRHS)
+ return Simplified;
+ }
+ }
+
+ return 0;
+}
+
+/// ThreadCmpOverSelect - In the case of a comparison with a select instruction,
+/// try to simplify the comparison by seeing whether both branches of the select
+/// result in the same value. Returns the common value if so, otherwise returns
+/// null.
+static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS,
+ Value *RHS, const TargetData *TD,
+ const DominatorTree *DT,
+ unsigned MaxRecurse) {
+ // Make sure the select is on the LHS.
+ if (!isa<SelectInst>(LHS)) {
+ std::swap(LHS, RHS);
+ Pred = CmpInst::getSwappedPredicate(Pred);
+ }
+ assert(isa<SelectInst>(LHS) && "Not comparing with a select instruction!");
+ SelectInst *SI = cast<SelectInst>(LHS);
+
+ // Now that we have "cmp select(cond, TV, FV), RHS", analyse it.
+ // Does "cmp TV, RHS" simplify?
+ if (Value *TCmp = SimplifyCmpInst(Pred, SI->getTrueValue(), RHS, TD, DT,
+ MaxRecurse))
+ // It does! Does "cmp FV, RHS" simplify?
+ if (Value *FCmp = SimplifyCmpInst(Pred, SI->getFalseValue(), RHS, TD, DT,
+ MaxRecurse))
+ // It does! If they simplified to the same value, then use it as the
+ // result of the original comparison.
+ if (TCmp == FCmp)
+ return TCmp;
+ return 0;
+}
+
+/// ThreadBinOpOverPHI - In the case of a binary operation with an operand that
+/// is a PHI instruction, try to simplify the binop by seeing whether evaluating
+/// it on the incoming phi values yields the same result for every value. If so
+/// returns the common value, otherwise returns null.
+static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT,
+ unsigned MaxRecurse) {
+ PHINode *PI;
+ if (isa<PHINode>(LHS)) {
+ PI = cast<PHINode>(LHS);
+ // Bail out if RHS and the phi may be mutually interdependent due to a loop.
+ if (!ValueDominatesPHI(RHS, PI, DT))
+ return 0;
+ } else {
+ assert(isa<PHINode>(RHS) && "No PHI instruction operand!");
+ PI = cast<PHINode>(RHS);
+ // Bail out if LHS and the phi may be mutually interdependent due to a loop.
+ if (!ValueDominatesPHI(LHS, PI, DT))
+ return 0;
+ }
+
+ // Evaluate the BinOp on the incoming phi values.
+ Value *CommonValue = 0;
+ for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
+ Value *Incoming = PI->getIncomingValue(i);
+ // If the incoming value is the phi node itself, it can safely be skipped.
+ if (Incoming == PI) continue;
+ Value *V = PI == LHS ?
+ SimplifyBinOp(Opcode, Incoming, RHS, TD, DT, MaxRecurse) :
+ SimplifyBinOp(Opcode, LHS, Incoming, TD, DT, MaxRecurse);
+ // If the operation failed to simplify, or simplified to a different value
+ // to previously, then give up.
+ if (!V || (CommonValue && V != CommonValue))
+ return 0;
+ CommonValue = V;
+ }
+
+ return CommonValue;
+}
+
+/// ThreadCmpOverPHI - In the case of a comparison with a PHI instruction, try
+/// try to simplify the comparison by seeing whether comparing with all of the
+/// incoming phi values yields the same result every time. If so returns the
+/// common result, otherwise returns null.
+static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT,
+ unsigned MaxRecurse) {
+ // Make sure the phi is on the LHS.
+ if (!isa<PHINode>(LHS)) {
+ std::swap(LHS, RHS);
+ Pred = CmpInst::getSwappedPredicate(Pred);
+ }
+ assert(isa<PHINode>(LHS) && "Not comparing with a phi instruction!");
+ PHINode *PI = cast<PHINode>(LHS);
+
+ // Bail out if RHS and the phi may be mutually interdependent due to a loop.
+ if (!ValueDominatesPHI(RHS, PI, DT))
+ return 0;
+
+ // Evaluate the BinOp on the incoming phi values.
+ Value *CommonValue = 0;
+ for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
+ Value *Incoming = PI->getIncomingValue(i);
+ // If the incoming value is the phi node itself, it can safely be skipped.
+ if (Incoming == PI) continue;
+ Value *V = SimplifyCmpInst(Pred, Incoming, RHS, TD, DT, MaxRecurse);
+ // If the operation failed to simplify, or simplified to a different value
+ // to previously, then give up.
+ if (!V || (CommonValue && V != CommonValue))
+ return 0;
+ CommonValue = V;
+ }
+
+ return CommonValue;
+}
+
/// SimplifyAddInst - Given operands for an Add, see if we can
/// fold the result. If not, this returns null.
Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
- const TargetData *TD) {
+ const TargetData *TD, const DominatorTree *) {
if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
Constant *Ops[] = { CLHS, CRHS };
return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(),
Ops, 2, TD);
}
-
+
// Canonicalize the constant to the RHS.
std::swap(Op0, Op1);
}
-
+
if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
// X + undef -> undef
if (isa<UndefValue>(Op1C))
return Op1C;
-
+
// X + 0 --> X
if (Op1C->isNullValue())
return Op0;
}
-
+
// FIXME: Could pull several more out of instcombine.
+
+ // Threading Add over selects and phi nodes is pointless, so don't bother.
+ // Threading over the select in "A + select(cond, B, C)" means evaluating
+ // "A+B" and "A+C" and seeing if they are equal; but they are equal if and
+ // only if B and C are equal. If B and C are equal then (since we assume
+ // that operands have already been simplified) "select(cond, B, C)" should
+ // have been simplified to the common value of B and C already. Analysing
+ // "A+B" and "A+C" thus gains nothing, but costs compile time. Similarly
+ // for threading over phi nodes.
+
return 0;
}
/// SimplifyAndInst - Given operands for an And, see if we can
/// fold the result. If not, this returns null.
-Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD) {
+static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
+ const DominatorTree *DT, unsigned MaxRecurse) {
if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
Constant *Ops[] = { CLHS, CRHS };
return ConstantFoldInstOperands(Instruction::And, CLHS->getType(),
Ops, 2, TD);
}
-
+
// Canonicalize the constant to the RHS.
std::swap(Op0, Op1);
}
-
+
// X & undef -> 0
if (isa<UndefValue>(Op1))
return Constant::getNullValue(Op0->getType());
-
+
// X & X = X
if (Op0 == Op1)
return Op0;
-
- // X & <0,0> = <0,0>
- if (isa<ConstantAggregateZero>(Op1))
+
+ // X & 0 = 0
+ if (match(Op1, m_Zero()))
return Op1;
-
- // X & <-1,-1> = X
- if (ConstantVector *CP = dyn_cast<ConstantVector>(Op1))
- if (CP->isAllOnesValue())
- return Op0;
-
- if (ConstantInt *Op1CI = dyn_cast<ConstantInt>(Op1)) {
- // X & 0 = 0
- if (Op1CI->isZero())
- return Op1CI;
- // X & -1 = X
- if (Op1CI->isAllOnesValue())
- return Op0;
- }
-
+
+ // X & -1 = X
+ if (match(Op1, m_AllOnes()))
+ return Op0;
+
// A & ~A = ~A & A = 0
- Value *A, *B;
+ Value *A = 0, *B = 0;
if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
(match(Op1, m_Not(m_Value(A))) && A == Op0))
return Constant::getNullValue(Op0->getType());
-
+
// (A | ?) & A = A
if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
(A == Op1 || B == Op1))
return Op1;
-
+
// A & (A | ?) = A
if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
(A == Op0 || B == Op0))
return Op0;
-
+
// (A & B) & A -> A & B
if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
(A == Op1 || B == Op1))
(A == Op0 || B == Op0))
return Op1;
+ // If the operation is with the result of a select instruction, check whether
+ // operating on either branch of the select always yields the same value.
+ if (MaxRecurse && (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)))
+ if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, TD, DT,
+ MaxRecurse-1))
+ return V;
+
+ // If the operation is with the result of a phi instruction, check whether
+ // operating on all incoming values of the phi always yields the same value.
+ if (MaxRecurse && (isa<PHINode>(Op0) || isa<PHINode>(Op1)))
+ if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, TD, DT,
+ MaxRecurse-1))
+ return V;
+
return 0;
}
+Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
+ const DominatorTree *DT) {
+ return ::SimplifyAndInst(Op0, Op1, TD, DT, RecursionLimit);
+}
+
/// SimplifyOrInst - Given operands for an Or, see if we can
/// fold the result. If not, this returns null.
-Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD) {
+static Value *SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
+ const DominatorTree *DT, unsigned MaxRecurse) {
if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
Constant *Ops[] = { CLHS, CRHS };
return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(),
Ops, 2, TD);
}
-
+
// Canonicalize the constant to the RHS.
std::swap(Op0, Op1);
}
-
+
// X | undef -> -1
if (isa<UndefValue>(Op1))
return Constant::getAllOnesValue(Op0->getType());
-
+
// X | X = X
if (Op0 == Op1)
return Op0;
- // X | <0,0> = X
- if (isa<ConstantAggregateZero>(Op1))
+ // X | 0 = X
+ if (match(Op1, m_Zero()))
return Op0;
-
- // X | <-1,-1> = <-1,-1>
- if (ConstantVector *CP = dyn_cast<ConstantVector>(Op1))
- if (CP->isAllOnesValue())
- return Op1;
-
- if (ConstantInt *Op1CI = dyn_cast<ConstantInt>(Op1)) {
- // X | 0 = X
- if (Op1CI->isZero())
- return Op0;
- // X | -1 = -1
- if (Op1CI->isAllOnesValue())
- return Op1CI;
- }
-
+
+ // X | -1 = -1
+ if (match(Op1, m_AllOnes()))
+ return Op1;
+
// A | ~A = ~A | A = -1
- Value *A, *B;
+ Value *A = 0, *B = 0;
if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
(match(Op1, m_Not(m_Value(A))) && A == Op0))
return Constant::getAllOnesValue(Op0->getType());
-
+
// (A & ?) | A = A
if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
(A == Op1 || B == Op1))
return Op1;
-
+
// A | (A & ?) = A
if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
(A == Op0 || B == Op0))
return Op0;
-
+
// (A | B) | A -> A | B
if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
(A == Op1 || B == Op1))
(A == Op0 || B == Op0))
return Op1;
+ // If the operation is with the result of a select instruction, check whether
+ // operating on either branch of the select always yields the same value.
+ if (MaxRecurse && (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)))
+ if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, TD, DT,
+ MaxRecurse-1))
+ return V;
+
+ // If the operation is with the result of a phi instruction, check whether
+ // operating on all incoming values of the phi always yields the same value.
+ if (MaxRecurse && (isa<PHINode>(Op0) || isa<PHINode>(Op1)))
+ if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, TD, DT,
+ MaxRecurse-1))
+ return V;
+
+ return 0;
+}
+
+Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
+ const DominatorTree *DT) {
+ return ::SimplifyOrInst(Op0, Op1, TD, DT, RecursionLimit);
+}
+
+/// SimplifyXorInst - Given operands for a Xor, see if we can
+/// fold the result. If not, this returns null.
+static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
+ const DominatorTree *DT, unsigned MaxRecurse) {
+ if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
+ if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
+ Constant *Ops[] = { CLHS, CRHS };
+ return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(),
+ Ops, 2, TD);
+ }
+
+ // Canonicalize the constant to the RHS.
+ std::swap(Op0, Op1);
+ }
+
+ // A ^ undef -> undef
+ if (isa<UndefValue>(Op1))
+ return UndefValue::get(Op0->getType());
+
+ // A ^ 0 = A
+ if (match(Op1, m_Zero()))
+ return Op0;
+
+ // A ^ A = 0
+ if (Op0 == Op1)
+ return Constant::getNullValue(Op0->getType());
+
+ // A ^ ~A = ~A ^ A = -1
+ Value *A = 0, *B = 0;
+ if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
+ (match(Op1, m_Not(m_Value(A))) && A == Op0))
+ return Constant::getAllOnesValue(Op0->getType());
+
+ // (A ^ B) ^ A = B
+ if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
+ (A == Op1 || B == Op1))
+ return A == Op1 ? B : A;
+
+ // A ^ (A ^ B) = B
+ if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
+ (A == Op0 || B == Op0))
+ return A == Op0 ? B : A;
+
+ // Threading Xor over selects and phi nodes is pointless, so don't bother.
+ // Threading over the select in "A ^ select(cond, B, C)" means evaluating
+ // "A^B" and "A^C" and seeing if they are equal; but they are equal if and
+ // only if B and C are equal. If B and C are equal then (since we assume
+ // that operands have already been simplified) "select(cond, B, C)" should
+ // have been simplified to the common value of B and C already. Analysing
+ // "A^B" and "A^C" thus gains nothing, but costs compile time. Similarly
+ // for threading over phi nodes.
+
return 0;
}
+Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
+ const DominatorTree *DT) {
+ return ::SimplifyXorInst(Op0, Op1, TD, DT, RecursionLimit);
+}
static const Type *GetCompareTy(Value *Op) {
return CmpInst::makeCmpResultType(Op->getType());
}
-
/// SimplifyICmpInst - Given operands for an ICmpInst, see if we can
/// fold the result. If not, this returns null.
-Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
- const TargetData *TD) {
+static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT,
+ unsigned MaxRecurse) {
CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!");
-
+
if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
if (Constant *CRHS = dyn_cast<Constant>(RHS))
return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD);
std::swap(LHS, RHS);
Pred = CmpInst::getSwappedPredicate(Pred);
}
-
+
// ITy - This is the return type of the compare we're considering.
const Type *ITy = GetCompareTy(LHS);
-
+
// icmp X, X -> true/false
// X icmp undef -> true/false. For example, icmp ugt %X, undef -> false
// because X could be 0.
if (LHS == RHS || isa<UndefValue>(RHS))
return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred));
-
+
// icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value
// addresses never equal each other! We already know that Op0 != Op1.
- if ((isa<GlobalValue>(LHS) || isa<AllocaInst>(LHS) ||
+ if ((isa<GlobalValue>(LHS) || isa<AllocaInst>(LHS) ||
isa<ConstantPointerNull>(LHS)) &&
- (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) ||
+ (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) ||
isa<ConstantPointerNull>(RHS)))
return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
-
+
// See if we are doing a comparison with a constant.
if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
// If we have an icmp le or icmp ge instruction, turn it into the
break;
}
}
-
-
+
+ // If the comparison is with the result of a select instruction, check whether
+ // comparing with either branch of the select always yields the same value.
+ if (MaxRecurse && (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)))
+ if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse-1))
+ return V;
+
+ // If the comparison is with the result of a phi instruction, check whether
+ // doing the compare with each incoming phi value yields a common result.
+ if (MaxRecurse && (isa<PHINode>(LHS) || isa<PHINode>(RHS)))
+ if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse-1))
+ return V;
+
return 0;
}
+Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT) {
+ return ::SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
+}
+
/// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can
/// fold the result. If not, this returns null.
-Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
- const TargetData *TD) {
+static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT,
+ unsigned MaxRecurse) {
CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate;
assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!");
if (Constant *CLHS = dyn_cast<Constant>(LHS)) {
if (Constant *CRHS = dyn_cast<Constant>(RHS))
return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD);
-
+
// If we have a constant, make sure it is on the RHS.
std::swap(LHS, RHS);
Pred = CmpInst::getSwappedPredicate(Pred);
}
-
+
// Fold trivial predicates.
if (Pred == FCmpInst::FCMP_FALSE)
return ConstantInt::get(GetCompareTy(LHS), 0);
if (CmpInst::isFalseWhenEqual(Pred))
return ConstantInt::get(GetCompareTy(LHS), 0);
}
-
+
// Handle fcmp with constant RHS
if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
// If the constant is a nan, see if we can fold the comparison based on it.
}
}
}
-
+
+ // If the comparison is with the result of a select instruction, check whether
+ // comparing with either branch of the select always yields the same value.
+ if (MaxRecurse && (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)))
+ if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse-1))
+ return V;
+
+ // If the comparison is with the result of a phi instruction, check whether
+ // doing the compare with each incoming phi value yields a common result.
+ if (MaxRecurse && (isa<PHINode>(LHS) || isa<PHINode>(RHS)))
+ if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse-1))
+ return V;
+
return 0;
}
+Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT) {
+ return ::SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
+}
+
/// SimplifySelectInst - Given operands for a SelectInst, see if we can fold
/// the result. If not, this returns null.
Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal,
- const TargetData *TD) {
+ const TargetData *TD, const DominatorTree *) {
// select true, X, Y -> X
// select false, X, Y -> Y
if (ConstantInt *CB = dyn_cast<ConstantInt>(CondVal))
return CB->getZExtValue() ? TrueVal : FalseVal;
-
+
// select C, X, X -> X
if (TrueVal == FalseVal)
return TrueVal;
-
+
if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
return FalseVal;
if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
return TrueVal;
return FalseVal;
}
-
-
-
+
return 0;
}
-
/// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can
/// fold the result. If not, this returns null.
Value *llvm::SimplifyGEPInst(Value *const *Ops, unsigned NumOps,
- const TargetData *TD) {
+ const TargetData *TD, const DominatorTree *) {
+ // The type of the GEP pointer operand.
+ const PointerType *PtrTy = cast<PointerType>(Ops[0]->getType());
+
// getelementptr P -> P.
if (NumOps == 1)
return Ops[0];
- // TODO.
- //if (isa<UndefValue>(Ops[0]))
- // return UndefValue::get(GEP.getType());
+ if (isa<UndefValue>(Ops[0])) {
+ // Compute the (pointer) type returned by the GEP instruction.
+ const Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, &Ops[1],
+ NumOps-1);
+ const Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace());
+ return UndefValue::get(GEPTy);
+ }
- // getelementptr P, 0 -> P.
- if (NumOps == 2)
+ if (NumOps == 2) {
+ // getelementptr P, 0 -> P.
if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1]))
if (C->isZero())
return Ops[0];
-
+ // getelementptr P, N -> P if P points to a type of zero size.
+ if (TD) {
+ const Type *Ty = PtrTy->getElementType();
+ if (Ty->isSized() && TD->getTypeAllocSize(Ty) == 0)
+ return Ops[0];
+ }
+ }
+
// Check to see if this is constant foldable.
for (unsigned i = 0; i != NumOps; ++i)
if (!isa<Constant>(Ops[i]))
return 0;
-
+
return ConstantExpr::getGetElementPtr(cast<Constant>(Ops[0]),
(Constant *const*)Ops+1, NumOps-1);
}
+/// SimplifyPHINode - See if we can fold the given phi. If not, returns null.
+static Value *SimplifyPHINode(PHINode *PN, const DominatorTree *DT) {
+ // If all of the PHI's incoming values are the same then replace the PHI node
+ // with the common value.
+ Value *CommonValue = 0;
+ bool HasUndefInput = false;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ Value *Incoming = PN->getIncomingValue(i);
+ // If the incoming value is the phi node itself, it can safely be skipped.
+ if (Incoming == PN) continue;
+ if (isa<UndefValue>(Incoming)) {
+ // Remember that we saw an undef value, but otherwise ignore them.
+ HasUndefInput = true;
+ continue;
+ }
+ if (CommonValue && Incoming != CommonValue)
+ return 0; // Not the same, bail out.
+ CommonValue = Incoming;
+ }
+
+ // If CommonValue is null then all of the incoming values were either undef or
+ // equal to the phi node itself.
+ if (!CommonValue)
+ return UndefValue::get(PN->getType());
+
+ // If we have a PHI node like phi(X, undef, X), where X is defined by some
+ // instruction, we cannot return X as the result of the PHI node unless it
+ // dominates the PHI block.
+ if (HasUndefInput)
+ return ValueDominatesPHI(CommonValue, PN, DT) ? CommonValue : 0;
+
+ return CommonValue;
+}
+
//=== Helper functions for higher up the class hierarchy.
/// SimplifyBinOp - Given operands for a BinaryOperator, see if we can
/// fold the result. If not, this returns null.
-Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
- const TargetData *TD) {
+static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT,
+ unsigned MaxRecurse) {
switch (Opcode) {
- case Instruction::And: return SimplifyAndInst(LHS, RHS, TD);
- case Instruction::Or: return SimplifyOrInst(LHS, RHS, TD);
+ case Instruction::And: return SimplifyAndInst(LHS, RHS, TD, DT, MaxRecurse);
+ case Instruction::Or: return SimplifyOrInst(LHS, RHS, TD, DT, MaxRecurse);
default:
if (Constant *CLHS = dyn_cast<Constant>(LHS))
if (Constant *CRHS = dyn_cast<Constant>(RHS)) {
Constant *COps[] = {CLHS, CRHS};
return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, 2, TD);
}
+
+ // If the operation is with the result of a select instruction, check whether
+ // operating on either branch of the select always yields the same value.
+ if (MaxRecurse && (isa<SelectInst>(LHS) || isa<SelectInst>(RHS)))
+ if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, TD, DT,
+ MaxRecurse-1))
+ return V;
+
+ // If the operation is with the result of a phi instruction, check whether
+ // operating on all incoming values of the phi always yields the same value.
+ if (MaxRecurse && (isa<PHINode>(LHS) || isa<PHINode>(RHS)))
+ if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, TD, DT, MaxRecurse-1))
+ return V;
+
return 0;
}
}
+Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT) {
+ return ::SimplifyBinOp(Opcode, LHS, RHS, TD, DT, RecursionLimit);
+}
+
/// SimplifyCmpInst - Given operands for a CmpInst, see if we can
/// fold the result.
-Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
- const TargetData *TD) {
+static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT,
+ unsigned MaxRecurse) {
if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate))
- return SimplifyICmpInst(Predicate, LHS, RHS, TD);
- return SimplifyFCmpInst(Predicate, LHS, RHS, TD);
+ return SimplifyICmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse);
+ return SimplifyFCmpInst(Predicate, LHS, RHS, TD, DT, MaxRecurse);
}
+Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
+ const TargetData *TD, const DominatorTree *DT) {
+ return ::SimplifyCmpInst(Predicate, LHS, RHS, TD, DT, RecursionLimit);
+}
/// SimplifyInstruction - See if we can compute a simplified version of this
/// instruction. If not, this returns null.
-Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) {
+Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD,
+ const DominatorTree *DT) {
+ Value *Result;
+
switch (I->getOpcode()) {
default:
- return ConstantFoldInstruction(I, TD);
+ Result = ConstantFoldInstruction(I, TD);
+ break;
case Instruction::Add:
- return SimplifyAddInst(I->getOperand(0), I->getOperand(1),
- cast<BinaryOperator>(I)->hasNoSignedWrap(),
- cast<BinaryOperator>(I)->hasNoUnsignedWrap(), TD);
+ Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1),
+ cast<BinaryOperator>(I)->hasNoSignedWrap(),
+ cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
+ TD, DT);
+ break;
case Instruction::And:
- return SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD);
+ Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT);
+ break;
case Instruction::Or:
- return SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD);
+ Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, DT);
+ break;
+ case Instruction::Xor:
+ Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), TD, DT);
+ break;
case Instruction::ICmp:
- return SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
- I->getOperand(0), I->getOperand(1), TD);
+ Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
+ I->getOperand(0), I->getOperand(1), TD, DT);
+ break;
case Instruction::FCmp:
- return SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
- I->getOperand(0), I->getOperand(1), TD);
+ Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
+ I->getOperand(0), I->getOperand(1), TD, DT);
+ break;
case Instruction::Select:
- return SimplifySelectInst(I->getOperand(0), I->getOperand(1),
- I->getOperand(2), TD);
+ Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1),
+ I->getOperand(2), TD, DT);
+ break;
case Instruction::GetElementPtr: {
SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
- return SimplifyGEPInst(&Ops[0], Ops.size(), TD);
+ Result = SimplifyGEPInst(&Ops[0], Ops.size(), TD, DT);
+ break;
}
+ case Instruction::PHI:
+ Result = SimplifyPHINode(cast<PHINode>(I), DT);
+ break;
}
+
+ /// If called on unreachable code, the above logic may report that the
+ /// instruction simplified to itself. Make life easier for users by
+ /// detecting that case here, returning null if it occurs.
+ return Result == I ? 0 : Result;
}
/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
/// simplifies and deletes scalar operations, it does not change the CFG.
///
void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
- const TargetData *TD) {
+ const TargetData *TD,
+ const DominatorTree *DT) {
assert(From != To && "ReplaceAndSimplifyAllUses(X,X) is not valid!");
-
+
// FromHandle/ToHandle - This keeps a WeakVH on the from/to values so that
// we can know if it gets deleted out from under us or replaced in a
// recursive simplification.
WeakVH FromHandle(From);
WeakVH ToHandle(To);
-
+
while (!From->use_empty()) {
// Update the instruction to use the new value.
Use &TheUse = From->use_begin().getUse();
// Sanity check to make sure 'User' doesn't dangle across
// SimplifyInstruction.
AssertingVH<> UserHandle(User);
-
- SimplifiedVal = SimplifyInstruction(User, TD);
+
+ SimplifiedVal = SimplifyInstruction(User, TD, DT);
if (SimplifiedVal == 0) continue;
}
-
+
// Recursively simplify this user to the new value.
- ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD);
+ ReplaceAndSimplifyAllUses(User, SimplifiedVal, TD, DT);
From = dyn_cast_or_null<Instruction>((Value*)FromHandle);
To = ToHandle;
-
+
assert(ToHandle && "To value deleted by recursive simplification?");
-
+
// If the recursive simplification ended up revisiting and deleting
// 'From' then we're done.
if (From == 0)
return;
}
-
+
// If 'From' has value handles referring to it, do a real RAUW to update them.
From->replaceAllUsesWith(To);
-
+
From->eraseFromParent();
}
-
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