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of why such threading is pointless. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119798 91177308-0d34-0410-b5e6-96231b3b80d8
912 lines
34 KiB
C++
912 lines
34 KiB
C++
//===- InstructionSimplify.cpp - Fold instruction operands ----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements routines for folding instructions into simpler forms
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// that do not require creating new instructions. For example, this does
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// constant folding, and can handle identities like (X&0)->0.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Support/PatternMatch.h"
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#include "llvm/Support/ValueHandle.h"
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using namespace llvm;
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using namespace llvm::PatternMatch;
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#define RecursionLimit 3
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static Value *SimplifyBinOp(unsigned, Value *, Value *, const TargetData *,
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const DominatorTree *, unsigned);
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static Value *SimplifyCmpInst(unsigned, Value *, Value *, const TargetData *,
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const DominatorTree *, unsigned);
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/// ValueDominatesPHI - Does the given value dominate the specified phi node?
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static bool ValueDominatesPHI(Value *V, PHINode *P, const DominatorTree *DT) {
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I)
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// Arguments and constants dominate all instructions.
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return true;
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// If we have a DominatorTree then do a precise test.
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if (DT)
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return DT->dominates(I, P);
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// Otherwise, if the instruction is in the entry block, and is not an invoke,
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// then it obviously dominates all phi nodes.
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if (I->getParent() == &I->getParent()->getParent()->getEntryBlock() &&
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!isa<InvokeInst>(I))
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return true;
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return false;
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}
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/// ThreadBinOpOverSelect - In the case of a binary operation with a select
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/// instruction as an operand, try to simplify the binop by seeing whether
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/// evaluating it on both branches of the select results in the same value.
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/// Returns the common value if so, otherwise returns null.
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static Value *ThreadBinOpOverSelect(unsigned Opcode, Value *LHS, Value *RHS,
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const TargetData *TD,
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const DominatorTree *DT,
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unsigned MaxRecurse) {
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SelectInst *SI;
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if (isa<SelectInst>(LHS)) {
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SI = cast<SelectInst>(LHS);
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} else {
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assert(isa<SelectInst>(RHS) && "No select instruction operand!");
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SI = cast<SelectInst>(RHS);
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}
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// Evaluate the BinOp on the true and false branches of the select.
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Value *TV;
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Value *FV;
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if (SI == LHS) {
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TV = SimplifyBinOp(Opcode, SI->getTrueValue(), RHS, TD, DT, MaxRecurse);
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FV = SimplifyBinOp(Opcode, SI->getFalseValue(), RHS, TD, DT, MaxRecurse);
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} else {
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TV = SimplifyBinOp(Opcode, LHS, SI->getTrueValue(), TD, DT, MaxRecurse);
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FV = SimplifyBinOp(Opcode, LHS, SI->getFalseValue(), TD, DT, MaxRecurse);
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}
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// If they simplified to the same value, then return the common value.
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// If they both failed to simplify then return null.
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if (TV == FV)
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return TV;
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// If one branch simplified to undef, return the other one.
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if (TV && isa<UndefValue>(TV))
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return FV;
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if (FV && isa<UndefValue>(FV))
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return TV;
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// If applying the operation did not change the true and false select values,
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// then the result of the binop is the select itself.
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if (TV == SI->getTrueValue() && FV == SI->getFalseValue())
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return SI;
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// If one branch simplified and the other did not, and the simplified
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// value is equal to the unsimplified one, return the simplified value.
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// For example, select (cond, X, X & Z) & Z -> X & Z.
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if ((FV && !TV) || (TV && !FV)) {
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// Check that the simplified value has the form "X op Y" where "op" is the
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// same as the original operation.
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Instruction *Simplified = dyn_cast<Instruction>(FV ? FV : TV);
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if (Simplified && Simplified->getOpcode() == Opcode) {
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// The value that didn't simplify is "UnsimplifiedLHS op UnsimplifiedRHS".
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// We already know that "op" is the same as for the simplified value. See
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// if the operands match too. If so, return the simplified value.
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Value *UnsimplifiedBranch = FV ? SI->getTrueValue() : SI->getFalseValue();
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Value *UnsimplifiedLHS = SI == LHS ? UnsimplifiedBranch : LHS;
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Value *UnsimplifiedRHS = SI == LHS ? RHS : UnsimplifiedBranch;
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if (Simplified->getOperand(0) == UnsimplifiedLHS &&
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Simplified->getOperand(1) == UnsimplifiedRHS)
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return Simplified;
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if (Simplified->isCommutative() &&
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Simplified->getOperand(1) == UnsimplifiedLHS &&
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Simplified->getOperand(0) == UnsimplifiedRHS)
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return Simplified;
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}
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}
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return 0;
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}
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/// ThreadCmpOverSelect - In the case of a comparison with a select instruction,
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/// try to simplify the comparison by seeing whether both branches of the select
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/// result in the same value. Returns the common value if so, otherwise returns
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/// null.
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static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS,
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Value *RHS, const TargetData *TD,
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const DominatorTree *DT,
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unsigned MaxRecurse) {
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// Make sure the select is on the LHS.
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if (!isa<SelectInst>(LHS)) {
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std::swap(LHS, RHS);
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Pred = CmpInst::getSwappedPredicate(Pred);
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}
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assert(isa<SelectInst>(LHS) && "Not comparing with a select instruction!");
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SelectInst *SI = cast<SelectInst>(LHS);
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// Now that we have "cmp select(cond, TV, FV), RHS", analyse it.
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// Does "cmp TV, RHS" simplify?
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if (Value *TCmp = SimplifyCmpInst(Pred, SI->getTrueValue(), RHS, TD, DT,
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MaxRecurse))
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// It does! Does "cmp FV, RHS" simplify?
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if (Value *FCmp = SimplifyCmpInst(Pred, SI->getFalseValue(), RHS, TD, DT,
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MaxRecurse))
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// It does! If they simplified to the same value, then use it as the
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// result of the original comparison.
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if (TCmp == FCmp)
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return TCmp;
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return 0;
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}
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/// ThreadBinOpOverPHI - In the case of a binary operation with an operand that
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/// is a PHI instruction, try to simplify the binop by seeing whether evaluating
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/// it on the incoming phi values yields the same result for every value. If so
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/// returns the common value, otherwise returns null.
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static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS,
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const TargetData *TD, const DominatorTree *DT,
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unsigned MaxRecurse) {
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PHINode *PI;
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if (isa<PHINode>(LHS)) {
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PI = cast<PHINode>(LHS);
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// Bail out if RHS and the phi may be mutually interdependent due to a loop.
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if (!ValueDominatesPHI(RHS, PI, DT))
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return 0;
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} else {
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assert(isa<PHINode>(RHS) && "No PHI instruction operand!");
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PI = cast<PHINode>(RHS);
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// Bail out if LHS and the phi may be mutually interdependent due to a loop.
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if (!ValueDominatesPHI(LHS, PI, DT))
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return 0;
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}
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// Evaluate the BinOp on the incoming phi values.
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Value *CommonValue = 0;
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for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
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Value *Incoming = PI->getIncomingValue(i);
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// If the incoming value is the phi node itself, it can safely be skipped.
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if (Incoming == PI) continue;
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Value *V = PI == LHS ?
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SimplifyBinOp(Opcode, Incoming, RHS, TD, DT, MaxRecurse) :
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SimplifyBinOp(Opcode, LHS, Incoming, TD, DT, MaxRecurse);
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// If the operation failed to simplify, or simplified to a different value
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// to previously, then give up.
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if (!V || (CommonValue && V != CommonValue))
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return 0;
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CommonValue = V;
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}
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return CommonValue;
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}
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/// ThreadCmpOverPHI - In the case of a comparison with a PHI instruction, try
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/// try to simplify the comparison by seeing whether comparing with all of the
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/// incoming phi values yields the same result every time. If so returns the
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/// common result, otherwise returns null.
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static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS,
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const TargetData *TD, const DominatorTree *DT,
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unsigned MaxRecurse) {
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// Make sure the phi is on the LHS.
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if (!isa<PHINode>(LHS)) {
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std::swap(LHS, RHS);
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Pred = CmpInst::getSwappedPredicate(Pred);
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}
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assert(isa<PHINode>(LHS) && "Not comparing with a phi instruction!");
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PHINode *PI = cast<PHINode>(LHS);
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// Bail out if RHS and the phi may be mutually interdependent due to a loop.
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if (!ValueDominatesPHI(RHS, PI, DT))
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return 0;
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// Evaluate the BinOp on the incoming phi values.
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Value *CommonValue = 0;
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for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) {
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Value *Incoming = PI->getIncomingValue(i);
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// If the incoming value is the phi node itself, it can safely be skipped.
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if (Incoming == PI) continue;
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Value *V = SimplifyCmpInst(Pred, Incoming, RHS, TD, DT, MaxRecurse);
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// If the operation failed to simplify, or simplified to a different value
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// to previously, then give up.
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if (!V || (CommonValue && V != CommonValue))
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return 0;
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CommonValue = V;
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}
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return CommonValue;
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}
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/// SimplifyAddInst - Given operands for an Add, see if we can
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/// fold the result. If not, this returns null.
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Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW,
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const TargetData *TD, const DominatorTree *) {
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if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
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if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
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Constant *Ops[] = { CLHS, CRHS };
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return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(),
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Ops, 2, TD);
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}
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// Canonicalize the constant to the RHS.
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std::swap(Op0, Op1);
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}
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if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
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// X + undef -> undef
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if (isa<UndefValue>(Op1C))
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return Op1C;
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// X + 0 --> X
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if (Op1C->isNullValue())
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return Op0;
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}
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// FIXME: Could pull several more out of instcombine.
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// Threading Add over selects and phi nodes is pointless, so don't bother.
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// Threading over the select in "A + select(cond, B, C)" means evaluating
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// "A+B" and "A+C" and seeing if they are equal; but they are equal if and
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// only if B and C are equal. If B and C are equal then (since we assume
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// that operands have already been simplified) "select(cond, B, C)" should
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// have been simplified to the common value of B and C already. Analysing
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// "A+B" and "A+C" thus gains nothing, but costs compile time. Similarly
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// for threading over phi nodes.
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return 0;
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}
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/// SimplifyAndInst - Given operands for an And, see if we can
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/// fold the result. If not, this returns null.
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static Value *SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
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const DominatorTree *DT, unsigned MaxRecurse) {
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if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
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if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
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Constant *Ops[] = { CLHS, CRHS };
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return ConstantFoldInstOperands(Instruction::And, CLHS->getType(),
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Ops, 2, TD);
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}
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// Canonicalize the constant to the RHS.
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std::swap(Op0, Op1);
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}
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// X & undef -> 0
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if (isa<UndefValue>(Op1))
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return Constant::getNullValue(Op0->getType());
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// X & X = X
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if (Op0 == Op1)
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return Op0;
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// X & 0 = 0
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if (match(Op1, m_Zero()))
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return Op1;
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// X & -1 = X
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if (match(Op1, m_AllOnes()))
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return Op0;
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// A & ~A = ~A & A = 0
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Value *A, *B;
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if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
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(match(Op1, m_Not(m_Value(A))) && A == Op0))
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return Constant::getNullValue(Op0->getType());
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// (A | ?) & A = A
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if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
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(A == Op1 || B == Op1))
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return Op1;
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// A & (A | ?) = A
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if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
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(A == Op0 || B == Op0))
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return Op0;
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// (A & B) & A -> A & B
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if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
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(A == Op1 || B == Op1))
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return Op0;
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// A & (A & B) -> A & B
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if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
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(A == Op0 || B == Op0))
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return Op1;
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// If the operation is with the result of a select instruction, check whether
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// operating on either branch of the select always yields the same value.
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if (MaxRecurse && (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)))
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if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, TD, DT,
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MaxRecurse-1))
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return V;
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// If the operation is with the result of a phi instruction, check whether
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// operating on all incoming values of the phi always yields the same value.
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if (MaxRecurse && (isa<PHINode>(Op0) || isa<PHINode>(Op1)))
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if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, TD, DT,
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MaxRecurse-1))
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return V;
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return 0;
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}
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Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const TargetData *TD,
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const DominatorTree *DT) {
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return ::SimplifyAndInst(Op0, Op1, TD, DT, RecursionLimit);
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}
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/// SimplifyOrInst - Given operands for an Or, see if we can
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/// fold the result. If not, this returns null.
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static Value *SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
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const DominatorTree *DT, unsigned MaxRecurse) {
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if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
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if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
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Constant *Ops[] = { CLHS, CRHS };
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return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(),
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Ops, 2, TD);
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}
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// Canonicalize the constant to the RHS.
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std::swap(Op0, Op1);
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}
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// X | undef -> -1
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if (isa<UndefValue>(Op1))
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return Constant::getAllOnesValue(Op0->getType());
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// X | X = X
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if (Op0 == Op1)
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return Op0;
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// X | 0 = X
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if (match(Op1, m_Zero()))
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return Op0;
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// X | -1 = -1
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if (match(Op1, m_AllOnes()))
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return Op1;
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// A | ~A = ~A | A = -1
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Value *A, *B;
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if ((match(Op0, m_Not(m_Value(A))) && A == Op1) ||
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(match(Op1, m_Not(m_Value(A))) && A == Op0))
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return Constant::getAllOnesValue(Op0->getType());
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// (A & ?) | A = A
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if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
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(A == Op1 || B == Op1))
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return Op1;
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// A | (A & ?) = A
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if (match(Op1, m_And(m_Value(A), m_Value(B))) &&
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(A == Op0 || B == Op0))
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return Op0;
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// (A | B) | A -> A | B
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if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
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(A == Op1 || B == Op1))
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return Op0;
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// A | (A | B) -> A | B
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if (match(Op1, m_Or(m_Value(A), m_Value(B))) &&
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(A == Op0 || B == Op0))
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return Op1;
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// If the operation is with the result of a select instruction, check whether
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// operating on either branch of the select always yields the same value.
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if (MaxRecurse && (isa<SelectInst>(Op0) || isa<SelectInst>(Op1)))
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if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, TD, DT,
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MaxRecurse-1))
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return V;
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// If the operation is with the result of a phi instruction, check whether
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// operating on all incoming values of the phi always yields the same value.
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if (MaxRecurse && (isa<PHINode>(Op0) || isa<PHINode>(Op1)))
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if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, TD, DT,
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MaxRecurse-1))
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return V;
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return 0;
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}
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Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const TargetData *TD,
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const DominatorTree *DT) {
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return ::SimplifyOrInst(Op0, Op1, TD, DT, RecursionLimit);
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}
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/// SimplifyXorInst - Given operands for a Xor, see if we can
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/// fold the result. If not, this returns null.
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static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
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const DominatorTree *DT, unsigned MaxRecurse) {
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if (Constant *CLHS = dyn_cast<Constant>(Op0)) {
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if (Constant *CRHS = dyn_cast<Constant>(Op1)) {
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Constant *Ops[] = { CLHS, CRHS };
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return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(),
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Ops, 2, TD);
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}
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// Canonicalize the constant to the RHS.
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std::swap(Op0, Op1);
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}
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// A ^ undef -> undef
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if (isa<UndefValue>(Op1))
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return UndefValue::get(Op0->getType());
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// A ^ 0 = A
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if (match(Op1, m_Zero()))
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return Op0;
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// A ^ A = 0
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if (Op0 == Op1)
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return Constant::getNullValue(Op0->getType());
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// A ^ ~A = ~A ^ A = -1
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Value *A, *B;
|
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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.
|
|
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);
|
|
}
|
|
|
|
// 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) ||
|
|
isa<ConstantPointerNull>(LHS)) &&
|
|
(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
|
|
// appropriate icmp lt or icmp gt instruction. This allows us to rely on
|
|
// them being folded in the code below.
|
|
switch (Pred) {
|
|
default: break;
|
|
case ICmpInst::ICMP_ULE:
|
|
if (CI->isMaxValue(false)) // A <=u MAX -> TRUE
|
|
return ConstantInt::getTrue(CI->getContext());
|
|
break;
|
|
case ICmpInst::ICMP_SLE:
|
|
if (CI->isMaxValue(true)) // A <=s MAX -> TRUE
|
|
return ConstantInt::getTrue(CI->getContext());
|
|
break;
|
|
case ICmpInst::ICMP_UGE:
|
|
if (CI->isMinValue(false)) // A >=u MIN -> TRUE
|
|
return ConstantInt::getTrue(CI->getContext());
|
|
break;
|
|
case ICmpInst::ICMP_SGE:
|
|
if (CI->isMinValue(true)) // A >=s MIN -> TRUE
|
|
return ConstantInt::getTrue(CI->getContext());
|
|
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.
|
|
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 (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 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 *) {
|
|
// getelementptr P -> P.
|
|
if (NumOps == 1)
|
|
return Ops[0];
|
|
|
|
// TODO.
|
|
//if (isa<UndefValue>(Ops[0]))
|
|
// return UndefValue::get(GEP.getType());
|
|
|
|
// getelementptr P, 0 -> P.
|
|
if (NumOps == 2)
|
|
if (ConstantInt *C = dyn_cast<ConstantInt>(Ops[1]))
|
|
if (C->isZero())
|
|
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::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.
|
|
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::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 null if it occurs.
|
|
return Result == I ? 0 : 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();
|
|
}
|