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llvm-6502/lib/Analysis/InstructionSimplify.cpp
Duncan Sands b2f3c383ec For completeness, generalize the (X + Y) - Y -> X transform and add X - (X + 1) -> -1. 
These were not recommended by my auto-simplifier since they don't fire often enough.
However they do fire from time to time, for example they remove one subtraction from
the final bitcode for 483.xalancbmk.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123755 91177308-0d34-0410-b5e6-96231b3b80d8
2011-01-18 11:50:19 +00:00

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//===- InstructionSimplify.cpp - Fold instruction operands ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements routines for folding instructions into simpler forms
// 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"). All operands are assumed to have already been
// simplified: This is usually true and assuming it simplifies the logic (if
// they have not been simplified then results are correct but maybe suboptimal).
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "instsimplify"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/ConstantFolding.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
STATISTIC(NumExpand, "Number of expansions");
STATISTIC(NumFactor , "Number of factorizations");
STATISTIC(NumReassoc, "Number of reassociations");
static Value *SimplifyAndInst(Value *, Value *, const TargetData *,
const DominatorTree *, unsigned);
static Value *SimplifyBinOp(unsigned, Value *, Value *, const TargetData *,
const DominatorTree *, unsigned);
static Value *SimplifyCmpInst(unsigned, Value *, Value *, const TargetData *,
const DominatorTree *, unsigned);
static Value *SimplifyOrInst(Value *, Value *, const TargetData *,
const DominatorTree *, unsigned);
static Value *SimplifyXorInst(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;
}
/// ExpandBinOp - Simplify "A op (B op' C)" by distributing op over op', turning
/// it into "(A op B) op' (A op C)". Here "op" is given by Opcode and "op'" is
/// given by OpcodeToExpand, while "A" corresponds to LHS and "B op' C" to RHS.
/// Also performs the transform "(A op' B) op C" -> "(A op C) op' (B op C)".
/// Returns the simplified value, or null if no simplification was performed.
static Value *ExpandBinOp(unsigned Opcode, Value *LHS, Value *RHS,
unsigned OpcToExpand, const TargetData *TD,
const DominatorTree *DT, unsigned MaxRecurse) {
Instruction::BinaryOps OpcodeToExpand = (Instruction::BinaryOps)OpcToExpand;
// Recursion is always used, so bail out at once if we already hit the limit.
if (!MaxRecurse--)
return 0;
// Check whether the expression has the form "(A op' B) op C".
if (BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS))
if (Op0->getOpcode() == OpcodeToExpand) {
// It does! Try turning it into "(A op C) op' (B op C)".
Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS;
// Do "A op C" and "B op C" both simplify?
if (Value *L = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse))
if (Value *R = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) {
// They do! Return "L op' R" if it simplifies or is already available.
// If "L op' R" equals "A op' B" then "L op' R" is just the LHS.
if ((L == A && R == B) || (Instruction::isCommutative(OpcodeToExpand)
&& L == B && R == A)) {
++NumExpand;
return LHS;
}
// Otherwise return "L op' R" if it simplifies.
if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT,
MaxRecurse)) {
++NumExpand;
return V;
}
}
}
// Check whether the expression has the form "A op (B op' C)".
if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS))
if (Op1->getOpcode() == OpcodeToExpand) {
// It does! Try turning it into "(A op B) op' (A op C)".
Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1);
// Do "A op B" and "A op C" both simplify?
if (Value *L = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse))
if (Value *R = SimplifyBinOp(Opcode, A, C, TD, DT, MaxRecurse)) {
// They do! Return "L op' R" if it simplifies or is already available.
// If "L op' R" equals "B op' C" then "L op' R" is just the RHS.
if ((L == B && R == C) || (Instruction::isCommutative(OpcodeToExpand)
&& L == C && R == B)) {
++NumExpand;
return RHS;
}
// Otherwise return "L op' R" if it simplifies.
if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, TD, DT,
MaxRecurse)) {
++NumExpand;
return V;
}
}
}
return 0;
}
/// FactorizeBinOp - Simplify "LHS Opcode RHS" by factorizing out a common term
/// using the operation OpCodeToExtract. For example, when Opcode is Add and
/// OpCodeToExtract is Mul then this tries to turn "(A*B)+(A*C)" into "A*(B+C)".
/// Returns the simplified value, or null if no simplification was performed.
static Value *FactorizeBinOp(unsigned Opcode, Value *LHS, Value *RHS,
unsigned OpcToExtract, const TargetData *TD,
const DominatorTree *DT, unsigned MaxRecurse) {
Instruction::BinaryOps OpcodeToExtract = (Instruction::BinaryOps)OpcToExtract;
// Recursion is always used, so bail out at once if we already hit the limit.
if (!MaxRecurse--)
return 0;
BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
if (!Op0 || Op0->getOpcode() != OpcodeToExtract ||
!Op1 || Op1->getOpcode() != OpcodeToExtract)
return 0;
// The expression has the form "(A op' B) op (C op' D)".
Value *A = Op0->getOperand(0), *B = Op0->getOperand(1);
Value *C = Op1->getOperand(0), *D = Op1->getOperand(1);
// Use left distributivity, i.e. "X op' (Y op Z) = (X op' Y) op (X op' Z)".
// Does the instruction have the form "(A op' B) op (A op' D)" or, in the
// commutative case, "(A op' B) op (C op' A)"?
if (A == C || (Instruction::isCommutative(OpcodeToExtract) && A == D)) {
Value *DD = A == C ? D : C;
// Form "A op' (B op DD)" if it simplifies completely.
// Does "B op DD" simplify?
if (Value *V = SimplifyBinOp(Opcode, B, DD, TD, DT, MaxRecurse)) {
// It does! Return "A op' V" if it simplifies or is already available.
// If V equals B then "A op' V" is just the LHS. If V equals DD then
// "A op' V" is just the RHS.
if (V == B || V == DD) {
++NumFactor;
return V == B ? LHS : RHS;
}
// Otherwise return "A op' V" if it simplifies.
if (Value *W = SimplifyBinOp(OpcodeToExtract, A, V, TD, DT, MaxRecurse)) {
++NumFactor;
return W;
}
}
}
// Use right distributivity, i.e. "(X op Y) op' Z = (X op' Z) op (Y op' Z)".
// Does the instruction have the form "(A op' B) op (C op' B)" or, in the
// commutative case, "(A op' B) op (B op' D)"?
if (B == D || (Instruction::isCommutative(OpcodeToExtract) && B == C)) {
Value *CC = B == D ? C : D;
// Form "(A op CC) op' B" if it simplifies completely..
// Does "A op CC" simplify?
if (Value *V = SimplifyBinOp(Opcode, A, CC, TD, DT, MaxRecurse)) {
// It does! Return "V op' B" if it simplifies or is already available.
// If V equals A then "V op' B" is just the LHS. If V equals CC then
// "V op' B" is just the RHS.
if (V == A || V == CC) {
++NumFactor;
return V == A ? LHS : RHS;
}
// Otherwise return "V op' B" if it simplifies.
if (Value *W = SimplifyBinOp(OpcodeToExtract, V, B, TD, DT, MaxRecurse)) {
++NumFactor;
return W;
}
}
}
return 0;
}
/// SimplifyAssociativeBinOp - Generic simplifications for associative binary
/// operations. Returns the simpler value, or null if none was found.
static Value *SimplifyAssociativeBinOp(unsigned Opc, Value *LHS, Value *RHS,
const TargetData *TD,
const DominatorTree *DT,
unsigned MaxRecurse) {
Instruction::BinaryOps Opcode = (Instruction::BinaryOps)Opc;
assert(Instruction::isAssociative(Opcode) && "Not an associative operation!");
// Recursion is always used, so bail out at once if we already hit the limit.
if (!MaxRecurse--)
return 0;
BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS);
BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS);
// Transform: "(A op B) op C" ==> "A op (B op C)" if it simplifies completely.
if (Op0 && Op0->getOpcode() == Opcode) {
Value *A = Op0->getOperand(0);
Value *B = Op0->getOperand(1);
Value *C = RHS;
// Does "B op C" simplify?
if (Value *V = SimplifyBinOp(Opcode, B, C, TD, DT, MaxRecurse)) {
// It does! Return "A op V" if it simplifies or is already available.
// If V equals B then "A op V" is just the LHS.
if (V == B) return LHS;
// Otherwise return "A op V" if it simplifies.
if (Value *W = SimplifyBinOp(Opcode, A, V, TD, DT, MaxRecurse)) {
++NumReassoc;
return W;
}
}
}
// Transform: "A op (B op C)" ==> "(A op B) op C" if it simplifies completely.
if (Op1 && Op1->getOpcode() == Opcode) {
Value *A = LHS;
Value *B = Op1->getOperand(0);
Value *C = Op1->getOperand(1);
// Does "A op B" simplify?
if (Value *V = SimplifyBinOp(Opcode, A, B, TD, DT, MaxRecurse)) {
// It does! Return "V op C" if it simplifies or is already available.
// If V equals B then "V op C" is just the RHS.
if (V == B) return RHS;
// Otherwise return "V op C" if it simplifies.
if (Value *W = SimplifyBinOp(Opcode, V, C, TD, DT, MaxRecurse)) {
++NumReassoc;
return W;
}
}
}
// The remaining transforms require commutativity as well as associativity.
if (!Instruction::isCommutative(Opcode))
return 0;
// Transform: "(A op B) op C" ==> "(C op A) op B" if it simplifies completely.
if (Op0 && Op0->getOpcode() == Opcode) {
Value *A = Op0->getOperand(0);
Value *B = Op0->getOperand(1);
Value *C = RHS;
// Does "C op A" simplify?
if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) {
// It does! Return "V op B" if it simplifies or is already available.
// If V equals A then "V op B" is just the LHS.
if (V == A) return LHS;
// Otherwise return "V op B" if it simplifies.
if (Value *W = SimplifyBinOp(Opcode, V, B, TD, DT, MaxRecurse)) {
++NumReassoc;
return W;
}
}
}
// Transform: "A op (B op C)" ==> "B op (C op A)" if it simplifies completely.
if (Op1 && Op1->getOpcode() == Opcode) {
Value *A = LHS;
Value *B = Op1->getOperand(0);
Value *C = Op1->getOperand(1);
// Does "C op A" simplify?
if (Value *V = SimplifyBinOp(Opcode, C, A, TD, DT, MaxRecurse)) {
// It does! Return "B op V" if it simplifies or is already available.
// If V equals C then "B op V" is just the RHS.
if (V == C) return RHS;
// Otherwise return "B op V" if it simplifies.
if (Value *W = SimplifyBinOp(Opcode, B, V, TD, DT, MaxRecurse)) {
++NumReassoc;
return W;
}
}
}
return 0;
}
/// 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) {
// Recursion is always used, so bail out at once if we already hit the limit.
if (!MaxRecurse--)
return 0;
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) {
// Recursion is always used, so bail out at once if we already hit the limit.
if (!MaxRecurse--)
return 0;
// 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) {
// Recursion is always used, so bail out at once if we already hit the limit.
if (!MaxRecurse--)
return 0;
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) {
// Recursion is always used, so bail out at once if we already hit the limit.
if (!MaxRecurse--)
return 0;
// 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.
static Value *SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
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::Add, CLHS->getType(),
Ops, 2, TD);
}
// Canonicalize the constant to the RHS.
std::swap(Op0, Op1);
}
// X + undef -> undef
if (isa<UndefValue>(Op1))
return Op1;
// X + 0 -> X
if (match(Op1, m_Zero()))
return Op0;
// X + (Y - X) -> Y
// (Y - X) + X -> Y
// Eg: X + -X -> 0
Value *Y = 0;
if (match(Op1, m_Sub(m_Value(Y), m_Specific(Op0))) ||
match(Op0, m_Sub(m_Value(Y), m_Specific(Op1))))
return Y;
// X + ~X -> -1 since ~X = -X-1
if (match(Op0, m_Not(m_Specific(Op1))) ||
match(Op1, m_Not(m_Specific(Op0))))
return Constant::getAllOnesValue(Op0->getType());
/// i1 add -> xor.
if (MaxRecurse && Op0->getType()->isIntegerTy(1))
if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1))
return V;
// Try some generic simplifications for associative operations.
if (Value *V = SimplifyAssociativeBinOp(Instruction::Add, Op0, Op1, TD, DT,
MaxRecurse))
return V;
// Mul distributes over Add. Try some generic simplifications based on this.
if (Value *V = FactorizeBinOp(Instruction::Add, Op0, Op1, Instruction::Mul,
TD, DT, MaxRecurse))
return V;
// 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;
}
Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
const TargetData *TD, const DominatorTree *DT) {
return ::SimplifyAddInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit);
}
/// SimplifySubInst - Given operands for a Sub, see if we can
/// fold the result. If not, this returns null.
static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
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::Sub, CLHS->getType(),
Ops, 2, TD);
}
// X - undef -> undef
// undef - X -> undef
if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1))
return UndefValue::get(Op0->getType());
// X - 0 -> X
if (match(Op1, m_Zero()))
return Op0;
// X - X -> 0
if (Op0 == Op1)
return Constant::getNullValue(Op0->getType());
// (X*2) - X -> X
// (X<<1) - X -> X
Value *X = 0;
if (match(Op0, m_Mul(m_Specific(Op1), m_ConstantInt<2>())) ||
match(Op0, m_Shl(m_Specific(Op1), m_One())))
return Op1;
// (X + Y) - Z -> X + (Y - Z) or Y + (X - Z) if everything simplifies.
// For example, (X + Y) - Y -> X; (Y + X) - Y -> X
Value *Y = 0, *Z = Op1;
if (MaxRecurse && match(Op0, m_Add(m_Value(X), m_Value(Y)))) { // (X + Y) - Z
// See if "V === Y - Z" simplifies.
if (Value *V = SimplifyBinOp(Instruction::Sub, Y, Z, TD, DT, MaxRecurse-1))
// It does! Now see if "X + V" simplifies.
if (Value *W = SimplifyBinOp(Instruction::Add, X, V, TD, DT,
MaxRecurse-1)) {
// It does, we successfully reassociated!
++NumReassoc;
return W;
}
// See if "V === X - Z" simplifies.
if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, TD, DT, MaxRecurse-1))
// It does! Now see if "Y + V" simplifies.
if (Value *W = SimplifyBinOp(Instruction::Add, Y, V, TD, DT,
MaxRecurse-1)) {
// It does, we successfully reassociated!
++NumReassoc;
return W;
}
}
// X - (Y + Z) -> (X - Y) - Z or (X - Z) - Y if everything simplifies.
// For example, X - (X + 1) -> -1
X = Op0;
if (MaxRecurse && match(Op1, m_Add(m_Value(Y), m_Value(Z)))) { // X - (Y + Z)
// See if "V === X - Y" simplifies.
if (Value *V = SimplifyBinOp(Instruction::Sub, X, Y, TD, DT, MaxRecurse-1))
// It does! Now see if "V - Z" simplifies.
if (Value *W = SimplifyBinOp(Instruction::Sub, V, Z, TD, DT,
MaxRecurse-1)) {
// It does, we successfully reassociated!
++NumReassoc;
return W;
}
// See if "V === X - Z" simplifies.
if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, TD, DT, MaxRecurse-1))
// It does! Now see if "V - Y" simplifies.
if (Value *W = SimplifyBinOp(Instruction::Sub, V, Y, TD, DT,
MaxRecurse-1)) {
// It does, we successfully reassociated!
++NumReassoc;
return W;
}
}
// Z - (X - Y) -> (Z - X) + Y if everything simplifies.
// For example, X - (X - Y) -> Y.
Z = Op0;
if (MaxRecurse && match(Op1, m_Sub(m_Value(X), m_Value(Y)))) // Z - (X - Y)
// See if "V === Z - X" simplifies.
if (Value *V = SimplifyBinOp(Instruction::Sub, Z, X, TD, DT, MaxRecurse-1))
// It does! Now see if "V + Y" simplifies.
if (Value *W = SimplifyBinOp(Instruction::Add, V, Y, TD, DT,
MaxRecurse-1)) {
// It does, we successfully reassociated!
++NumReassoc;
return W;
}
// Mul distributes over Sub. Try some generic simplifications based on this.
if (Value *V = FactorizeBinOp(Instruction::Sub, Op0, Op1, Instruction::Mul,
TD, DT, MaxRecurse))
return V;
// i1 sub -> xor.
if (MaxRecurse && Op0->getType()->isIntegerTy(1))
if (Value *V = SimplifyXorInst(Op0, Op1, TD, DT, MaxRecurse-1))
return V;
// Threading Sub 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::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
const TargetData *TD, const DominatorTree *DT) {
return ::SimplifySubInst(Op0, Op1, isNSW, isNUW, TD, DT, RecursionLimit);
}
/// SimplifyMulInst - Given operands for a Mul, see if we can
/// fold the result. If not, this returns null.
static Value *SimplifyMulInst(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::Mul, 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 * 0 -> 0
if (match(Op1, m_Zero()))
return Op1;
// X * 1 -> X
if (match(Op1, m_One()))
return Op0;
/// i1 mul -> and.
if (MaxRecurse && Op0->getType()->isIntegerTy(1))
if (Value *V = SimplifyAndInst(Op0, Op1, TD, DT, MaxRecurse-1))
return V;
// Try some generic simplifications for associative operations.
if (Value *V = SimplifyAssociativeBinOp(Instruction::Mul, Op0, Op1, TD, DT,
MaxRecurse))
return V;
// Mul distributes over Add. Try some generic simplifications based on this.
if (Value *V = ExpandBinOp(Instruction::Mul, Op0, Op1, Instruction::Add,
TD, DT, MaxRecurse))
return V;
// 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 (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
if (Value *V = ThreadBinOpOverSelect(Instruction::Mul, Op0, Op1, TD, DT,
MaxRecurse))
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 (isa<PHINode>(Op0) || isa<PHINode>(Op1))
if (Value *V = ThreadBinOpOverPHI(Instruction::Mul, Op0, Op1, TD, DT,
MaxRecurse))
return V;
return 0;
}
Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
const DominatorTree *DT) {
return ::SimplifyMulInst(Op0, Op1, TD, DT, RecursionLimit);
}
/// SimplifyShift - Given operands for an Shl, LShr or AShr, see if we can
/// fold the result. If not, this returns null.
static Value *SimplifyShift(unsigned Opcode, Value *Op0, Value *Op1,
const TargetData *TD, const DominatorTree *DT,
unsigned MaxRecurse) {
if (Constant *C0 = dyn_cast<Constant>(Op0)) {
if (Constant *C1 = dyn_cast<Constant>(Op1)) {
Constant *Ops[] = { C0, C1 };
return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, 2, TD);
}
}
// 0 shift by X -> 0
if (match(Op0, m_Zero()))
return Op0;
// X shift by 0 -> X
if (match(Op1, m_Zero()))
return Op0;
// X shift by undef -> undef because it may shift by the bitwidth.
if (isa<UndefValue>(Op1))
return Op1;
// Shifting by the bitwidth or more is undefined.
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1))
if (CI->getValue().getLimitedValue() >=
Op0->getType()->getScalarSizeInBits())
return UndefValue::get(Op0->getType());
// 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 (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, TD, DT, MaxRecurse))
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 (isa<PHINode>(Op0) || isa<PHINode>(Op1))
if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, TD, DT, MaxRecurse))
return V;
return 0;
}
/// SimplifyShlInst - Given operands for an Shl, see if we can
/// fold the result. If not, this returns null.
static Value *SimplifyShlInst(Value *Op0, Value *Op1, const TargetData *TD,
const DominatorTree *DT, unsigned MaxRecurse) {
if (Value *V = SimplifyShift(Instruction::Shl, Op0, Op1, TD, DT, MaxRecurse))
return V;
// undef << X -> 0
if (isa<UndefValue>(Op0))
return Constant::getNullValue(Op0->getType());
return 0;
}
Value *llvm::SimplifyShlInst(Value *Op0, Value *Op1, const TargetData *TD,
const DominatorTree *DT) {
return ::SimplifyShlInst(Op0, Op1, TD, DT, RecursionLimit);
}
/// SimplifyLShrInst - Given operands for an LShr, see if we can
/// fold the result. If not, this returns null.
static Value *SimplifyLShrInst(Value *Op0, Value *Op1, const TargetData *TD,
const DominatorTree *DT, unsigned MaxRecurse) {
if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, TD, DT, MaxRecurse))
return V;
// undef >>l X -> 0
if (isa<UndefValue>(Op0))
return Constant::getNullValue(Op0->getType());
return 0;
}
Value *llvm::SimplifyLShrInst(Value *Op0, Value *Op1, const TargetData *TD,
const DominatorTree *DT) {
return ::SimplifyLShrInst(Op0, Op1, TD, DT, RecursionLimit);
}
/// SimplifyAShrInst - Given operands for an AShr, see if we can
/// fold the result. If not, this returns null.
static Value *SimplifyAShrInst(Value *Op0, Value *Op1, const TargetData *TD,
const DominatorTree *DT, unsigned MaxRecurse) {
if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, TD, DT, MaxRecurse))
return V;
// all ones >>a X -> all ones
if (match(Op0, m_AllOnes()))
return Op0;
// undef >>a X -> all ones
if (isa<UndefValue>(Op0))
return Constant::getAllOnesValue(Op0->getType());
return 0;
}
Value *llvm::SimplifyAShrInst(Value *Op0, Value *Op1, const TargetData *TD,
const DominatorTree *DT) {
return ::SimplifyAShrInst(Op0, Op1, TD, DT, RecursionLimit);
}
/// SimplifyAndInst - Given operands for an And, see if we can
/// fold the result. If not, this returns null.
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
if (match(Op1, m_Zero()))
return Op1;
// X & -1 = X
if (match(Op1, m_AllOnes()))
return Op0;
// A & ~A = ~A & A = 0
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;
// Try some generic simplifications for associative operations.
if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, TD, DT,
MaxRecurse))
return V;
// And distributes over Or. Try some generic simplifications based on this.
if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Or,
TD, DT, MaxRecurse))
return V;
// And distributes over Xor. Try some generic simplifications based on this.
if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Xor,
TD, DT, MaxRecurse))
return V;
// Or distributes over And. Try some generic simplifications based on this.
if (Value *V = FactorizeBinOp(Instruction::And, Op0, Op1, Instruction::Or,
TD, DT, MaxRecurse))
return V;
// 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 (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, TD, DT,
MaxRecurse))
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 (isa<PHINode>(Op0) || isa<PHINode>(Op1))
if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, TD, DT,
MaxRecurse))
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.
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 = X
if (match(Op1, m_Zero()))
return Op0;
// X | -1 = -1
if (match(Op1, m_AllOnes()))
return Op1;
// 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 & ?) | 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;
// Try some generic simplifications for associative operations.
if (Value *V = SimplifyAssociativeBinOp(Instruction::Or, Op0, Op1, TD, DT,
MaxRecurse))
return V;
// Or distributes over And. Try some generic simplifications based on this.
if (Value *V = ExpandBinOp(Instruction::Or, Op0, Op1, Instruction::And,
TD, DT, MaxRecurse))
return V;
// And distributes over Or. Try some generic simplifications based on this.
if (Value *V = FactorizeBinOp(Instruction::Or, Op0, Op1, Instruction::And,
TD, DT, MaxRecurse))
return V;
// 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 (isa<SelectInst>(Op0) || isa<SelectInst>(Op1))
if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, TD, DT,
MaxRecurse))
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 (isa<PHINode>(Op0) || isa<PHINode>(Op1))
if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, TD, DT,
MaxRecurse))
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 Op1;
// 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;
if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
(match(Op1, m_Not(m_Value(A))) && A == Op0))
return Constant::getAllOnesValue(Op0->getType());
// Try some generic simplifications for associative operations.
if (Value *V = SimplifyAssociativeBinOp(Instruction::Xor, Op0, Op1, TD, DT,
MaxRecurse))
return V;
// And distributes over Xor. Try some generic simplifications based on this.
if (Value *V = FactorizeBinOp(Instruction::Xor, Op0, Op1, Instruction::And,
TD, DT, MaxRecurse))
return V;
// 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.
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);
// If we have a constant, make sure it is on the RHS.
std::swap(LHS, RHS);
Pred = CmpInst::getSwappedPredicate(Pred);
}
const Type *ITy = GetCompareTy(LHS); // The return type.
const Type *OpTy = LHS->getType(); // The operand type.
// 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));
// Special case logic when the operands have i1 type.
if (OpTy->isIntegerTy(1) || (OpTy->isVectorTy() &&
cast<VectorType>(OpTy)->getElementType()->isIntegerTy(1))) {
switch (Pred) {
default: break;
case ICmpInst::ICMP_EQ:
// X == 1 -> X
if (match(RHS, m_One()))
return LHS;
break;
case ICmpInst::ICMP_NE:
// X != 0 -> X
if (match(RHS, m_Zero()))
return LHS;
break;
case ICmpInst::ICMP_UGT:
// X >u 0 -> X
if (match(RHS, m_Zero()))
return LHS;
break;
case ICmpInst::ICMP_UGE:
// X >=u 1 -> X
if (match(RHS, m_One()))
return LHS;
break;
case ICmpInst::ICMP_SLT:
// X <s 0 -> X
if (match(RHS, m_Zero()))
return LHS;
break;
case ICmpInst::ICMP_SLE:
// X <=s -1 -> X
if (match(RHS, m_One()))
return LHS;
break;
}
}
// See if we are doing a comparison with a constant.
if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
switch (Pred) {
default: break;
case ICmpInst::ICMP_UGT:
if (CI->isMaxValue(false)) // A >u MAX -> FALSE
return ConstantInt::getFalse(CI->getContext());
break;
case ICmpInst::ICMP_UGE:
if (CI->isMinValue(false)) // A >=u MIN -> TRUE
return ConstantInt::getTrue(CI->getContext());
break;
case ICmpInst::ICMP_ULT:
if (CI->isMinValue(false)) // A <u MIN -> FALSE
return ConstantInt::getFalse(CI->getContext());
break;
case ICmpInst::ICMP_ULE:
if (CI->isMaxValue(false)) // A <=u MAX -> TRUE
return ConstantInt::getTrue(CI->getContext());
break;
case ICmpInst::ICMP_SGT:
if (CI->isMaxValue(true)) // A >s MAX -> FALSE
return ConstantInt::getFalse(CI->getContext());
break;
case ICmpInst::ICMP_SGE:
if (CI->isMinValue(true)) // A >=s MIN -> TRUE
return ConstantInt::getTrue(CI->getContext());
break;
case ICmpInst::ICMP_SLT:
if (CI->isMinValue(true)) // A <s MIN -> FALSE
return ConstantInt::getFalse(CI->getContext());
break;
case ICmpInst::ICMP_SLE:
if (CI->isMaxValue(true)) // A <=s MAX -> TRUE
return ConstantInt::getTrue(CI->getContext());
break;
}
}
// icmp <alloca*>, <global/alloca*/null> - Different stack variables have
// different addresses, and what's more the address of a stack variable is
// never null or equal to the address of a global. Note that generalizing
// to the case where LHS is a global variable address or null is pointless,
// since if both LHS and RHS are constants then we already constant folded
// the compare, and if only one of them is then we moved it to RHS already.
if (isa<AllocaInst>(LHS) && (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) ||
isa<ConstantPointerNull>(RHS)))
// We already know that LHS != LHS.
return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
// 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<SelectInst>(LHS) || isa<SelectInst>(RHS))
if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse))
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 (isa<PHINode>(LHS) || isa<PHINode>(RHS))
if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse))
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.
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 (Pred == FCmpInst::FCMP_TRUE)
return ConstantInt::get(GetCompareTy(LHS), 1);
if (isa<UndefValue>(RHS)) // fcmp pred X, undef -> undef
return UndefValue::get(GetCompareTy(LHS));
// fcmp x,x -> true/false. Not all compares are foldable.
if (LHS == RHS) {
if (CmpInst::isTrueWhenEqual(Pred))
return ConstantInt::get(GetCompareTy(LHS), 1);
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 (ConstantFP *CFP = dyn_cast<ConstantFP>(RHSC)) {
if (CFP->getValueAPF().isNaN()) {
if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo"
return ConstantInt::getFalse(CFP->getContext());
assert(FCmpInst::isUnordered(Pred) &&
"Comparison must be either ordered or unordered!");
// True if unordered.
return ConstantInt::getTrue(CFP->getContext());
}
// Check whether the constant is an infinity.
if (CFP->getValueAPF().isInfinity()) {
if (CFP->getValueAPF().isNegative()) {
switch (Pred) {
case FCmpInst::FCMP_OLT:
// No value is ordered and less than negative infinity.
return ConstantInt::getFalse(CFP->getContext());
case FCmpInst::FCMP_UGE:
// All values are unordered with or at least negative infinity.
return ConstantInt::getTrue(CFP->getContext());
default:
break;
}
} else {
switch (Pred) {
case FCmpInst::FCMP_OGT:
// No value is ordered and greater than infinity.
return ConstantInt::getFalse(CFP->getContext());
case FCmpInst::FCMP_ULE:
// All values are unordered with and at most infinity.
return ConstantInt::getTrue(CFP->getContext());
default:
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 (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, TD, DT, MaxRecurse))
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 (isa<PHINode>(LHS) || isa<PHINode>(RHS))
if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, TD, DT, MaxRecurse))
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 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;
if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
if (isa<Constant>(TrueVal))
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 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];
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);
}
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.
static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
const TargetData *TD, const DominatorTree *DT,
unsigned MaxRecurse) {
switch (Opcode) {
case Instruction::Add: return SimplifyAddInst(LHS, RHS, /* isNSW */ false,
/* isNUW */ false, TD, DT,
MaxRecurse);
case Instruction::Sub: return SimplifySubInst(LHS, RHS, /* isNSW */ false,
/* isNUW */ false, TD, DT,
MaxRecurse);
case Instruction::Mul: return SimplifyMulInst(LHS, RHS, TD, DT, MaxRecurse);
case Instruction::Shl: return SimplifyShlInst(LHS, RHS, TD, DT, MaxRecurse);
case Instruction::LShr: return SimplifyLShrInst(LHS, RHS, TD, DT, MaxRecurse);
case Instruction::AShr: return SimplifyAShrInst(LHS, RHS, TD, DT, MaxRecurse);
case Instruction::And: return SimplifyAndInst(LHS, RHS, TD, DT, MaxRecurse);
case Instruction::Or: return SimplifyOrInst(LHS, RHS, TD, DT, MaxRecurse);
case Instruction::Xor: return SimplifyXorInst(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 associative, try some generic simplifications.
if (Instruction::isAssociative(Opcode))
if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, TD, DT,
MaxRecurse))
return V;
// 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 (isa<SelectInst>(LHS) || isa<SelectInst>(RHS))
if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, TD, DT,
MaxRecurse))
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 (isa<PHINode>(LHS) || isa<PHINode>(RHS))
if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, TD, DT, MaxRecurse))
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.
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, 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,
const DominatorTree *DT) {
Value *Result;
switch (I->getOpcode()) {
default:
Result = ConstantFoldInstruction(I, TD);
break;
case Instruction::Add:
Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1),
cast<BinaryOperator>(I)->hasNoSignedWrap(),
cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
TD, DT);
break;
case Instruction::Sub:
Result = SimplifySubInst(I->getOperand(0), I->getOperand(1),
cast<BinaryOperator>(I)->hasNoSignedWrap(),
cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
TD, DT);
break;
case Instruction::Mul:
Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), TD, DT);
break;
case Instruction::Shl:
Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1), TD, DT);
break;
case Instruction::LShr:
Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1), TD, DT);
break;
case Instruction::AShr:
Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1), TD, DT);
break;
case Instruction::And:
Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT);
break;
case Instruction::Or:
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:
Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
I->getOperand(0), I->getOperand(1), TD, DT);
break;
case Instruction::FCmp:
Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
I->getOperand(0), I->getOperand(1), TD, DT);
break;
case Instruction::Select:
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());
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 a safe value instead.
return Result == I ? UndefValue::get(I->getType()) : Result;
}
/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
/// delete the From instruction. In addition to a basic RAUW, this does a
/// recursive simplification of the newly formed instructions. This catches
/// things where one simplification exposes other opportunities. This only
/// simplifies and deletes scalar operations, it does not change the CFG.
///
void llvm::ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
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();
Instruction *User = cast<Instruction>(TheUse.getUser());
TheUse = To;
// Check to see if the instruction can be folded due to the operand
// replacement. For example changing (or X, Y) into (or X, -1) can replace
// the 'or' with -1.
Value *SimplifiedVal;
{
// Sanity check to make sure 'User' doesn't dangle across
// SimplifyInstruction.
AssertingVH<> UserHandle(User);
SimplifiedVal = SimplifyInstruction(User, TD, DT);
if (SimplifiedVal == 0) continue;
}
// Recursively simplify this user to the new value.
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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