X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FAnalysis%2FInstructionSimplify.cpp;h=87125191ad0e77f429e177add08af6e2148b9ce6;hb=ed58a6f96f605901adc0df3ca76499d52b2d1a1a;hp=66452a5d9865fa8634817f97dee3612b2f895125;hpb=92826def593df7a422c7b07f09342febce81ddd3;p=oota-llvm.git diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp index 66452a5d986..87125191ad0 100644 --- a/lib/Analysis/InstructionSimplify.cpp +++ b/lib/Analysis/InstructionSimplify.cpp @@ -8,104 +8,311 @@ //===----------------------------------------------------------------------===// // // 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(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(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(LHS)) { + SI = cast(LHS); + } else { + assert(isa(RHS) && "No select instruction operand!"); + SI = cast(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(TV)) + return FV; + if (FV && isa(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(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(LHS)) { + std::swap(LHS, RHS); + Pred = CmpInst::getSwappedPredicate(Pred); + } + assert(isa(LHS) && "Not comparing with a select instruction!"); + SelectInst *SI = cast(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(LHS)) { + PI = cast(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(RHS) && "No PHI instruction operand!"); + PI = cast(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(LHS)) { + std::swap(LHS, RHS); + Pred = CmpInst::getSwappedPredicate(Pred); + } + assert(isa(LHS) && "Not comparing with a phi instruction!"); + PHINode *PI = cast(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(Op0)) { if (Constant *CRHS = dyn_cast(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(Op1)) { // X + undef -> undef if (isa(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(Op0)) { if (Constant *CRHS = dyn_cast(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(Op1)) return Constant::getNullValue(Op0->getType()); - + // X & X = X if (Op0 == Op1) return Op0; - - // X & <0,0> = <0,0> - if (isa(Op1)) + + // X & 0 = 0 + if (match(Op1, m_Zero())) return Op1; - - // X & <-1,-1> = X - if (ConstantVector *CP = dyn_cast(Op1)) - if (CP->isAllOnesValue()) - return Op0; - - if (ConstantInt *Op1CI = dyn_cast(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)) @@ -116,65 +323,75 @@ Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD) { (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(Op0) || isa(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(Op0) || isa(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(Op0)) { if (Constant *CRHS = dyn_cast(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(Op1)) return Constant::getAllOnesValue(Op0->getType()); - + // X | X = X if (Op0 == Op1) return Op0; - // X | <0,0> = X - if (isa(Op1)) + // X | 0 = X + if (match(Op1, m_Zero())) return Op0; - - // X | <-1,-1> = <-1,-1> - if (ConstantVector *CP = dyn_cast(Op1)) - if (CP->isAllOnesValue()) - return Op1; - - if (ConstantInt *Op1CI = dyn_cast(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)) @@ -185,22 +402,100 @@ Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD) { (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(Op0) || isa(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(Op0) || isa(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(Op0)) { + if (Constant *CRHS = dyn_cast(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(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(LHS)) { if (Constant *CRHS = dyn_cast(RHS)) return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, TD); @@ -209,24 +504,24 @@ Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, 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(RHS)) return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred)); - + // icmp , - Global/Stack value // addresses never equal each other! We already know that Op0 != Op1. - if ((isa(LHS) || isa(LHS) || + if ((isa(LHS) || isa(LHS) || isa(LHS)) && - (isa(RHS) || isa(RHS) || + (isa(RHS) || isa(RHS) || isa(RHS))) return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred)); - + // See if we are doing a comparison with a constant. if (ConstantInt *CI = dyn_cast(RHS)) { // If we have an icmp le or icmp ge instruction, turn it into the @@ -255,43 +550,41 @@ Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, // 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 (isa(LHS) || isa(RHS)) { - // Make sure the select is on the LHS. - if (!isa(LHS)) { - std::swap(LHS, RHS); - Pred = CmpInst::getSwappedPredicate(Pred); - } - SelectInst *SI = cast(LHS); - // Now that we have "icmp select(cond, TV, FV), RHS", analyse it. - // Does "icmp TV, RHS" simplify? - if (Value *TCmp = SimplifyICmpInst(Pred, SI->getTrueValue(), RHS, TD)) - // It does! Does "icmp FV, RHS" simplify? - if (Value *FCmp = SimplifyICmpInst(Pred, SI->getFalseValue(), RHS, TD)) - // It does! If they simplified to the same value, then use it as the - // result of the original comparison. - if (TCmp == FCmp) - return TCmp; - } + if (MaxRecurse && (isa(LHS) || isa(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(LHS) || isa(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(LHS)) { if (Constant *CRHS = dyn_cast(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); @@ -308,7 +601,7 @@ Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, if (CmpInst::isFalseWhenEqual(Pred)) return ConstantInt::get(GetCompareTy(LHS), 0); } - + // Handle fcmp with constant RHS if (Constant *RHSC = dyn_cast(RHS)) { // If the constant is a nan, see if we can fold the comparison based on it. @@ -349,43 +642,40 @@ Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, } } } - + // 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 (isa(LHS) || isa(RHS)) { - // Make sure the select is on the LHS. - if (!isa(LHS)) { - std::swap(LHS, RHS); - Pred = CmpInst::getSwappedPredicate(Pred); - } - SelectInst *SI = cast(LHS); - // Now that we have "fcmp select(cond, TV, FV), RHS", analyse it. - // Does "fcmp TV, RHS" simplify? - if (Value *TCmp = SimplifyFCmpInst(Pred, SI->getTrueValue(), RHS, TD)) - // It does! Does "fcmp FV, RHS" simplify? - if (Value *FCmp = SimplifyFCmpInst(Pred, SI->getFalseValue(), RHS, TD)) - // It does! If they simplified to the same value, then use it as the - // result of the original comparison. - if (TCmp == FCmp) - return TCmp; - } + if (MaxRecurse && (isa(LHS) || isa(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(LHS) || isa(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(CondVal)) return CB->getZExtValue() ? TrueVal : FalseVal; - + // select C, X, X -> X if (TrueVal == FalseVal) return TrueVal; - + if (isa(TrueVal)) // select C, undef, X -> X return FalseVal; if (isa(FalseVal)) // select C, X, undef -> X @@ -395,98 +685,191 @@ Value *llvm::SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal, 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(Ops[0]->getType()); + // getelementptr P -> P. if (NumOps == 1) return Ops[0]; - // TODO. - //if (isa(Ops[0])) - // return UndefValue::get(GEP.getType()); + if (isa(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(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(Ops[i])) return 0; - + return ConstantExpr::getGetElementPtr(cast(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(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(LHS)) if (Constant *CRHS = dyn_cast(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(LHS) || isa(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(LHS) || isa(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(I)->hasNoSignedWrap(), - cast(I)->hasNoUnsignedWrap(), TD); + Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1), + cast(I)->hasNoSignedWrap(), + cast(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(I)->getPredicate(), - I->getOperand(0), I->getOperand(1), TD); + Result = SimplifyICmpInst(cast(I)->getPredicate(), + I->getOperand(0), I->getOperand(1), TD, DT); + break; case Instruction::FCmp: - return SimplifyFCmpInst(cast(I)->getPredicate(), - I->getOperand(0), I->getOperand(1), TD); + Result = SimplifyFCmpInst(cast(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 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(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 @@ -496,15 +879,16 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) { /// 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(); @@ -519,27 +903,26 @@ void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To, // 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((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(); } -