mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2025-11-04 05:17:07 +00:00
11acaa374c
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92760 91177308-0d34-0410-b5e6-96231b3b80d8
704 lines
27 KiB
C++
704 lines
27 KiB
C++
//===- InstCombineSelect.cpp ----------------------------------------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the visitSelect function.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "InstCombine.h"
|
|
#include "llvm/Support/PatternMatch.h"
|
|
using namespace llvm;
|
|
using namespace PatternMatch;
|
|
|
|
/// MatchSelectPattern - Pattern match integer [SU]MIN, [SU]MAX, and ABS idioms,
|
|
/// returning the kind and providing the out parameter results if we
|
|
/// successfully match.
|
|
static SelectPatternFlavor
|
|
MatchSelectPattern(Value *V, Value *&LHS, Value *&RHS) {
|
|
SelectInst *SI = dyn_cast<SelectInst>(V);
|
|
if (SI == 0) return SPF_UNKNOWN;
|
|
|
|
ICmpInst *ICI = dyn_cast<ICmpInst>(SI->getCondition());
|
|
if (ICI == 0) return SPF_UNKNOWN;
|
|
|
|
LHS = ICI->getOperand(0);
|
|
RHS = ICI->getOperand(1);
|
|
|
|
// (icmp X, Y) ? X : Y
|
|
if (SI->getTrueValue() == ICI->getOperand(0) &&
|
|
SI->getFalseValue() == ICI->getOperand(1)) {
|
|
switch (ICI->getPredicate()) {
|
|
default: return SPF_UNKNOWN; // Equality.
|
|
case ICmpInst::ICMP_UGT:
|
|
case ICmpInst::ICMP_UGE: return SPF_UMAX;
|
|
case ICmpInst::ICMP_SGT:
|
|
case ICmpInst::ICMP_SGE: return SPF_SMAX;
|
|
case ICmpInst::ICMP_ULT:
|
|
case ICmpInst::ICMP_ULE: return SPF_UMIN;
|
|
case ICmpInst::ICMP_SLT:
|
|
case ICmpInst::ICMP_SLE: return SPF_SMIN;
|
|
}
|
|
}
|
|
|
|
// (icmp X, Y) ? Y : X
|
|
if (SI->getTrueValue() == ICI->getOperand(1) &&
|
|
SI->getFalseValue() == ICI->getOperand(0)) {
|
|
switch (ICI->getPredicate()) {
|
|
default: return SPF_UNKNOWN; // Equality.
|
|
case ICmpInst::ICMP_UGT:
|
|
case ICmpInst::ICMP_UGE: return SPF_UMIN;
|
|
case ICmpInst::ICMP_SGT:
|
|
case ICmpInst::ICMP_SGE: return SPF_SMIN;
|
|
case ICmpInst::ICMP_ULT:
|
|
case ICmpInst::ICMP_ULE: return SPF_UMAX;
|
|
case ICmpInst::ICMP_SLT:
|
|
case ICmpInst::ICMP_SLE: return SPF_SMAX;
|
|
}
|
|
}
|
|
|
|
// TODO: (X > 4) ? X : 5 --> (X >= 5) ? X : 5 --> MAX(X, 5)
|
|
|
|
return SPF_UNKNOWN;
|
|
}
|
|
|
|
|
|
/// GetSelectFoldableOperands - We want to turn code that looks like this:
|
|
/// %C = or %A, %B
|
|
/// %D = select %cond, %C, %A
|
|
/// into:
|
|
/// %C = select %cond, %B, 0
|
|
/// %D = or %A, %C
|
|
///
|
|
/// Assuming that the specified instruction is an operand to the select, return
|
|
/// a bitmask indicating which operands of this instruction are foldable if they
|
|
/// equal the other incoming value of the select.
|
|
///
|
|
static unsigned GetSelectFoldableOperands(Instruction *I) {
|
|
switch (I->getOpcode()) {
|
|
case Instruction::Add:
|
|
case Instruction::Mul:
|
|
case Instruction::And:
|
|
case Instruction::Or:
|
|
case Instruction::Xor:
|
|
return 3; // Can fold through either operand.
|
|
case Instruction::Sub: // Can only fold on the amount subtracted.
|
|
case Instruction::Shl: // Can only fold on the shift amount.
|
|
case Instruction::LShr:
|
|
case Instruction::AShr:
|
|
return 1;
|
|
default:
|
|
return 0; // Cannot fold
|
|
}
|
|
}
|
|
|
|
/// GetSelectFoldableConstant - For the same transformation as the previous
|
|
/// function, return the identity constant that goes into the select.
|
|
static Constant *GetSelectFoldableConstant(Instruction *I) {
|
|
switch (I->getOpcode()) {
|
|
default: llvm_unreachable("This cannot happen!");
|
|
case Instruction::Add:
|
|
case Instruction::Sub:
|
|
case Instruction::Or:
|
|
case Instruction::Xor:
|
|
case Instruction::Shl:
|
|
case Instruction::LShr:
|
|
case Instruction::AShr:
|
|
return Constant::getNullValue(I->getType());
|
|
case Instruction::And:
|
|
return Constant::getAllOnesValue(I->getType());
|
|
case Instruction::Mul:
|
|
return ConstantInt::get(I->getType(), 1);
|
|
}
|
|
}
|
|
|
|
/// FoldSelectOpOp - Here we have (select c, TI, FI), and we know that TI and FI
|
|
/// have the same opcode and only one use each. Try to simplify this.
|
|
Instruction *InstCombiner::FoldSelectOpOp(SelectInst &SI, Instruction *TI,
|
|
Instruction *FI) {
|
|
if (TI->getNumOperands() == 1) {
|
|
// If this is a non-volatile load or a cast from the same type,
|
|
// merge.
|
|
if (TI->isCast()) {
|
|
if (TI->getOperand(0)->getType() != FI->getOperand(0)->getType())
|
|
return 0;
|
|
} else {
|
|
return 0; // unknown unary op.
|
|
}
|
|
|
|
// Fold this by inserting a select from the input values.
|
|
SelectInst *NewSI = SelectInst::Create(SI.getCondition(), TI->getOperand(0),
|
|
FI->getOperand(0), SI.getName()+".v");
|
|
InsertNewInstBefore(NewSI, SI);
|
|
return CastInst::Create(Instruction::CastOps(TI->getOpcode()), NewSI,
|
|
TI->getType());
|
|
}
|
|
|
|
// Only handle binary operators here.
|
|
if (!isa<BinaryOperator>(TI))
|
|
return 0;
|
|
|
|
// Figure out if the operations have any operands in common.
|
|
Value *MatchOp, *OtherOpT, *OtherOpF;
|
|
bool MatchIsOpZero;
|
|
if (TI->getOperand(0) == FI->getOperand(0)) {
|
|
MatchOp = TI->getOperand(0);
|
|
OtherOpT = TI->getOperand(1);
|
|
OtherOpF = FI->getOperand(1);
|
|
MatchIsOpZero = true;
|
|
} else if (TI->getOperand(1) == FI->getOperand(1)) {
|
|
MatchOp = TI->getOperand(1);
|
|
OtherOpT = TI->getOperand(0);
|
|
OtherOpF = FI->getOperand(0);
|
|
MatchIsOpZero = false;
|
|
} else if (!TI->isCommutative()) {
|
|
return 0;
|
|
} else if (TI->getOperand(0) == FI->getOperand(1)) {
|
|
MatchOp = TI->getOperand(0);
|
|
OtherOpT = TI->getOperand(1);
|
|
OtherOpF = FI->getOperand(0);
|
|
MatchIsOpZero = true;
|
|
} else if (TI->getOperand(1) == FI->getOperand(0)) {
|
|
MatchOp = TI->getOperand(1);
|
|
OtherOpT = TI->getOperand(0);
|
|
OtherOpF = FI->getOperand(1);
|
|
MatchIsOpZero = true;
|
|
} else {
|
|
return 0;
|
|
}
|
|
|
|
// If we reach here, they do have operations in common.
|
|
SelectInst *NewSI = SelectInst::Create(SI.getCondition(), OtherOpT,
|
|
OtherOpF, SI.getName()+".v");
|
|
InsertNewInstBefore(NewSI, SI);
|
|
|
|
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TI)) {
|
|
if (MatchIsOpZero)
|
|
return BinaryOperator::Create(BO->getOpcode(), MatchOp, NewSI);
|
|
else
|
|
return BinaryOperator::Create(BO->getOpcode(), NewSI, MatchOp);
|
|
}
|
|
llvm_unreachable("Shouldn't get here");
|
|
return 0;
|
|
}
|
|
|
|
static bool isSelect01(Constant *C1, Constant *C2) {
|
|
ConstantInt *C1I = dyn_cast<ConstantInt>(C1);
|
|
if (!C1I)
|
|
return false;
|
|
ConstantInt *C2I = dyn_cast<ConstantInt>(C2);
|
|
if (!C2I)
|
|
return false;
|
|
return (C1I->isZero() || C1I->isOne()) && (C2I->isZero() || C2I->isOne());
|
|
}
|
|
|
|
/// FoldSelectIntoOp - Try fold the select into one of the operands to
|
|
/// facilitate further optimization.
|
|
Instruction *InstCombiner::FoldSelectIntoOp(SelectInst &SI, Value *TrueVal,
|
|
Value *FalseVal) {
|
|
// See the comment above GetSelectFoldableOperands for a description of the
|
|
// transformation we are doing here.
|
|
if (Instruction *TVI = dyn_cast<Instruction>(TrueVal)) {
|
|
if (TVI->hasOneUse() && TVI->getNumOperands() == 2 &&
|
|
!isa<Constant>(FalseVal)) {
|
|
if (unsigned SFO = GetSelectFoldableOperands(TVI)) {
|
|
unsigned OpToFold = 0;
|
|
if ((SFO & 1) && FalseVal == TVI->getOperand(0)) {
|
|
OpToFold = 1;
|
|
} else if ((SFO & 2) && FalseVal == TVI->getOperand(1)) {
|
|
OpToFold = 2;
|
|
}
|
|
|
|
if (OpToFold) {
|
|
Constant *C = GetSelectFoldableConstant(TVI);
|
|
Value *OOp = TVI->getOperand(2-OpToFold);
|
|
// Avoid creating select between 2 constants unless it's selecting
|
|
// between 0 and 1.
|
|
if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
|
|
Instruction *NewSel = SelectInst::Create(SI.getCondition(), OOp, C);
|
|
InsertNewInstBefore(NewSel, SI);
|
|
NewSel->takeName(TVI);
|
|
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TVI))
|
|
return BinaryOperator::Create(BO->getOpcode(), FalseVal, NewSel);
|
|
llvm_unreachable("Unknown instruction!!");
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (Instruction *FVI = dyn_cast<Instruction>(FalseVal)) {
|
|
if (FVI->hasOneUse() && FVI->getNumOperands() == 2 &&
|
|
!isa<Constant>(TrueVal)) {
|
|
if (unsigned SFO = GetSelectFoldableOperands(FVI)) {
|
|
unsigned OpToFold = 0;
|
|
if ((SFO & 1) && TrueVal == FVI->getOperand(0)) {
|
|
OpToFold = 1;
|
|
} else if ((SFO & 2) && TrueVal == FVI->getOperand(1)) {
|
|
OpToFold = 2;
|
|
}
|
|
|
|
if (OpToFold) {
|
|
Constant *C = GetSelectFoldableConstant(FVI);
|
|
Value *OOp = FVI->getOperand(2-OpToFold);
|
|
// Avoid creating select between 2 constants unless it's selecting
|
|
// between 0 and 1.
|
|
if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
|
|
Instruction *NewSel = SelectInst::Create(SI.getCondition(), C, OOp);
|
|
InsertNewInstBefore(NewSel, SI);
|
|
NewSel->takeName(FVI);
|
|
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(FVI))
|
|
return BinaryOperator::Create(BO->getOpcode(), TrueVal, NewSel);
|
|
llvm_unreachable("Unknown instruction!!");
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/// visitSelectInstWithICmp - Visit a SelectInst that has an
|
|
/// ICmpInst as its first operand.
|
|
///
|
|
Instruction *InstCombiner::visitSelectInstWithICmp(SelectInst &SI,
|
|
ICmpInst *ICI) {
|
|
bool Changed = false;
|
|
ICmpInst::Predicate Pred = ICI->getPredicate();
|
|
Value *CmpLHS = ICI->getOperand(0);
|
|
Value *CmpRHS = ICI->getOperand(1);
|
|
Value *TrueVal = SI.getTrueValue();
|
|
Value *FalseVal = SI.getFalseValue();
|
|
|
|
// Check cases where the comparison is with a constant that
|
|
// can be adjusted to fit the min/max idiom. We may edit ICI in
|
|
// place here, so make sure the select is the only user.
|
|
if (ICI->hasOneUse())
|
|
if (ConstantInt *CI = dyn_cast<ConstantInt>(CmpRHS)) {
|
|
switch (Pred) {
|
|
default: break;
|
|
case ICmpInst::ICMP_ULT:
|
|
case ICmpInst::ICMP_SLT: {
|
|
// X < MIN ? T : F --> F
|
|
if (CI->isMinValue(Pred == ICmpInst::ICMP_SLT))
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
// X < C ? X : C-1 --> X > C-1 ? C-1 : X
|
|
Constant *AdjustedRHS =
|
|
ConstantInt::get(CI->getContext(), CI->getValue()-1);
|
|
if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
|
|
(CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
CmpRHS = AdjustedRHS;
|
|
std::swap(FalseVal, TrueVal);
|
|
ICI->setPredicate(Pred);
|
|
ICI->setOperand(1, CmpRHS);
|
|
SI.setOperand(1, TrueVal);
|
|
SI.setOperand(2, FalseVal);
|
|
Changed = true;
|
|
}
|
|
break;
|
|
}
|
|
case ICmpInst::ICMP_UGT:
|
|
case ICmpInst::ICMP_SGT: {
|
|
// X > MAX ? T : F --> F
|
|
if (CI->isMaxValue(Pred == ICmpInst::ICMP_SGT))
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
// X > C ? X : C+1 --> X < C+1 ? C+1 : X
|
|
Constant *AdjustedRHS =
|
|
ConstantInt::get(CI->getContext(), CI->getValue()+1);
|
|
if ((CmpLHS == TrueVal && AdjustedRHS == FalseVal) ||
|
|
(CmpLHS == FalseVal && AdjustedRHS == TrueVal)) {
|
|
Pred = ICmpInst::getSwappedPredicate(Pred);
|
|
CmpRHS = AdjustedRHS;
|
|
std::swap(FalseVal, TrueVal);
|
|
ICI->setPredicate(Pred);
|
|
ICI->setOperand(1, CmpRHS);
|
|
SI.setOperand(1, TrueVal);
|
|
SI.setOperand(2, FalseVal);
|
|
Changed = true;
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
|
|
// (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if signed
|
|
// (x >s -1) ? -1 : 0 -> ashr x, 31 -> all ones if not signed
|
|
CmpInst::Predicate Pred = CmpInst::BAD_ICMP_PREDICATE;
|
|
if (match(TrueVal, m_ConstantInt<-1>()) &&
|
|
match(FalseVal, m_ConstantInt<0>()))
|
|
Pred = ICI->getPredicate();
|
|
else if (match(TrueVal, m_ConstantInt<0>()) &&
|
|
match(FalseVal, m_ConstantInt<-1>()))
|
|
Pred = CmpInst::getInversePredicate(ICI->getPredicate());
|
|
|
|
if (Pred != CmpInst::BAD_ICMP_PREDICATE) {
|
|
// If we are just checking for a icmp eq of a single bit and zext'ing it
|
|
// to an integer, then shift the bit to the appropriate place and then
|
|
// cast to integer to avoid the comparison.
|
|
const APInt &Op1CV = CI->getValue();
|
|
|
|
// sext (x <s 0) to i32 --> x>>s31 true if signbit set.
|
|
// sext (x >s -1) to i32 --> (x>>s31)^-1 true if signbit clear.
|
|
if ((Pred == ICmpInst::ICMP_SLT && Op1CV == 0) ||
|
|
(Pred == ICmpInst::ICMP_SGT && Op1CV.isAllOnesValue())) {
|
|
Value *In = ICI->getOperand(0);
|
|
Value *Sh = ConstantInt::get(In->getType(),
|
|
In->getType()->getScalarSizeInBits()-1);
|
|
In = InsertNewInstBefore(BinaryOperator::CreateAShr(In, Sh,
|
|
In->getName()+".lobit"),
|
|
*ICI);
|
|
if (In->getType() != SI.getType())
|
|
In = CastInst::CreateIntegerCast(In, SI.getType(),
|
|
true/*SExt*/, "tmp", ICI);
|
|
|
|
if (Pred == ICmpInst::ICMP_SGT)
|
|
In = InsertNewInstBefore(BinaryOperator::CreateNot(In,
|
|
In->getName()+".not"), *ICI);
|
|
|
|
return ReplaceInstUsesWith(SI, In);
|
|
}
|
|
}
|
|
}
|
|
|
|
if (CmpLHS == TrueVal && CmpRHS == FalseVal) {
|
|
// Transform (X == Y) ? X : Y -> Y
|
|
if (Pred == ICmpInst::ICMP_EQ)
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
// Transform (X != Y) ? X : Y -> X
|
|
if (Pred == ICmpInst::ICMP_NE)
|
|
return ReplaceInstUsesWith(SI, TrueVal);
|
|
/// NOTE: if we wanted to, this is where to detect integer MIN/MAX
|
|
|
|
} else if (CmpLHS == FalseVal && CmpRHS == TrueVal) {
|
|
// Transform (X == Y) ? Y : X -> X
|
|
if (Pred == ICmpInst::ICMP_EQ)
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
// Transform (X != Y) ? Y : X -> Y
|
|
if (Pred == ICmpInst::ICMP_NE)
|
|
return ReplaceInstUsesWith(SI, TrueVal);
|
|
/// NOTE: if we wanted to, this is where to detect integer MIN/MAX
|
|
}
|
|
return Changed ? &SI : 0;
|
|
}
|
|
|
|
|
|
/// CanSelectOperandBeMappingIntoPredBlock - SI is a select whose condition is a
|
|
/// PHI node (but the two may be in different blocks). See if the true/false
|
|
/// values (V) are live in all of the predecessor blocks of the PHI. For
|
|
/// example, cases like this cannot be mapped:
|
|
///
|
|
/// X = phi [ C1, BB1], [C2, BB2]
|
|
/// Y = add
|
|
/// Z = select X, Y, 0
|
|
///
|
|
/// because Y is not live in BB1/BB2.
|
|
///
|
|
static bool CanSelectOperandBeMappingIntoPredBlock(const Value *V,
|
|
const SelectInst &SI) {
|
|
// If the value is a non-instruction value like a constant or argument, it
|
|
// can always be mapped.
|
|
const Instruction *I = dyn_cast<Instruction>(V);
|
|
if (I == 0) return true;
|
|
|
|
// If V is a PHI node defined in the same block as the condition PHI, we can
|
|
// map the arguments.
|
|
const PHINode *CondPHI = cast<PHINode>(SI.getCondition());
|
|
|
|
if (const PHINode *VP = dyn_cast<PHINode>(I))
|
|
if (VP->getParent() == CondPHI->getParent())
|
|
return true;
|
|
|
|
// Otherwise, if the PHI and select are defined in the same block and if V is
|
|
// defined in a different block, then we can transform it.
|
|
if (SI.getParent() == CondPHI->getParent() &&
|
|
I->getParent() != CondPHI->getParent())
|
|
return true;
|
|
|
|
// Otherwise we have a 'hard' case and we can't tell without doing more
|
|
// detailed dominator based analysis, punt.
|
|
return false;
|
|
}
|
|
|
|
/// FoldSPFofSPF - We have an SPF (e.g. a min or max) of an SPF of the form:
|
|
/// SPF2(SPF1(A, B), C)
|
|
Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
|
|
SelectPatternFlavor SPF1,
|
|
Value *A, Value *B,
|
|
Instruction &Outer,
|
|
SelectPatternFlavor SPF2, Value *C) {
|
|
if (C == A || C == B) {
|
|
// MAX(MAX(A, B), B) -> MAX(A, B)
|
|
// MIN(MIN(a, b), a) -> MIN(a, b)
|
|
if (SPF1 == SPF2)
|
|
return ReplaceInstUsesWith(Outer, Inner);
|
|
|
|
// MAX(MIN(a, b), a) -> a
|
|
// MIN(MAX(a, b), a) -> a
|
|
if ((SPF1 == SPF_SMIN && SPF2 == SPF_SMAX) ||
|
|
(SPF1 == SPF_SMAX && SPF2 == SPF_SMIN) ||
|
|
(SPF1 == SPF_UMIN && SPF2 == SPF_UMAX) ||
|
|
(SPF1 == SPF_UMAX && SPF2 == SPF_UMIN))
|
|
return ReplaceInstUsesWith(Outer, C);
|
|
}
|
|
|
|
// TODO: MIN(MIN(A, 23), 97)
|
|
return 0;
|
|
}
|
|
|
|
|
|
|
|
|
|
Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
|
|
Value *CondVal = SI.getCondition();
|
|
Value *TrueVal = SI.getTrueValue();
|
|
Value *FalseVal = SI.getFalseValue();
|
|
|
|
// select true, X, Y -> X
|
|
// select false, X, Y -> Y
|
|
if (ConstantInt *C = dyn_cast<ConstantInt>(CondVal))
|
|
return ReplaceInstUsesWith(SI, C->getZExtValue() ? TrueVal : FalseVal);
|
|
|
|
// select C, X, X -> X
|
|
if (TrueVal == FalseVal)
|
|
return ReplaceInstUsesWith(SI, TrueVal);
|
|
|
|
if (isa<UndefValue>(TrueVal)) // select C, undef, X -> X
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
if (isa<UndefValue>(FalseVal)) // select C, X, undef -> X
|
|
return ReplaceInstUsesWith(SI, TrueVal);
|
|
if (isa<UndefValue>(CondVal)) { // select undef, X, Y -> X or Y
|
|
if (isa<Constant>(TrueVal))
|
|
return ReplaceInstUsesWith(SI, TrueVal);
|
|
else
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
}
|
|
|
|
if (SI.getType()->isInteger(1)) {
|
|
if (ConstantInt *C = dyn_cast<ConstantInt>(TrueVal)) {
|
|
if (C->getZExtValue()) {
|
|
// Change: A = select B, true, C --> A = or B, C
|
|
return BinaryOperator::CreateOr(CondVal, FalseVal);
|
|
} else {
|
|
// Change: A = select B, false, C --> A = and !B, C
|
|
Value *NotCond =
|
|
InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
|
|
"not."+CondVal->getName()), SI);
|
|
return BinaryOperator::CreateAnd(NotCond, FalseVal);
|
|
}
|
|
} else if (ConstantInt *C = dyn_cast<ConstantInt>(FalseVal)) {
|
|
if (C->getZExtValue() == false) {
|
|
// Change: A = select B, C, false --> A = and B, C
|
|
return BinaryOperator::CreateAnd(CondVal, TrueVal);
|
|
} else {
|
|
// Change: A = select B, C, true --> A = or !B, C
|
|
Value *NotCond =
|
|
InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
|
|
"not."+CondVal->getName()), SI);
|
|
return BinaryOperator::CreateOr(NotCond, TrueVal);
|
|
}
|
|
}
|
|
|
|
// select a, b, a -> a&b
|
|
// select a, a, b -> a|b
|
|
if (CondVal == TrueVal)
|
|
return BinaryOperator::CreateOr(CondVal, FalseVal);
|
|
else if (CondVal == FalseVal)
|
|
return BinaryOperator::CreateAnd(CondVal, TrueVal);
|
|
}
|
|
|
|
// Selecting between two integer constants?
|
|
if (ConstantInt *TrueValC = dyn_cast<ConstantInt>(TrueVal))
|
|
if (ConstantInt *FalseValC = dyn_cast<ConstantInt>(FalseVal)) {
|
|
// select C, 1, 0 -> zext C to int
|
|
if (FalseValC->isZero() && TrueValC->getValue() == 1) {
|
|
return CastInst::Create(Instruction::ZExt, CondVal, SI.getType());
|
|
} else if (TrueValC->isZero() && FalseValC->getValue() == 1) {
|
|
// select C, 0, 1 -> zext !C to int
|
|
Value *NotCond =
|
|
InsertNewInstBefore(BinaryOperator::CreateNot(CondVal,
|
|
"not."+CondVal->getName()), SI);
|
|
return CastInst::Create(Instruction::ZExt, NotCond, SI.getType());
|
|
}
|
|
|
|
if (ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition())) {
|
|
// If one of the constants is zero (we know they can't both be) and we
|
|
// have an icmp instruction with zero, and we have an 'and' with the
|
|
// non-constant value, eliminate this whole mess. This corresponds to
|
|
// cases like this: ((X & 27) ? 27 : 0)
|
|
if (TrueValC->isZero() || FalseValC->isZero())
|
|
if (IC->isEquality() && isa<ConstantInt>(IC->getOperand(1)) &&
|
|
cast<Constant>(IC->getOperand(1))->isNullValue())
|
|
if (Instruction *ICA = dyn_cast<Instruction>(IC->getOperand(0)))
|
|
if (ICA->getOpcode() == Instruction::And &&
|
|
isa<ConstantInt>(ICA->getOperand(1)) &&
|
|
(ICA->getOperand(1) == TrueValC ||
|
|
ICA->getOperand(1) == FalseValC) &&
|
|
cast<ConstantInt>(ICA->getOperand(1))->getValue().isPowerOf2()) {
|
|
// Okay, now we know that everything is set up, we just don't
|
|
// know whether we have a icmp_ne or icmp_eq and whether the
|
|
// true or false val is the zero.
|
|
bool ShouldNotVal = !TrueValC->isZero();
|
|
ShouldNotVal ^= IC->getPredicate() == ICmpInst::ICMP_NE;
|
|
Value *V = ICA;
|
|
if (ShouldNotVal)
|
|
V = InsertNewInstBefore(BinaryOperator::Create(
|
|
Instruction::Xor, V, ICA->getOperand(1)), SI);
|
|
return ReplaceInstUsesWith(SI, V);
|
|
}
|
|
}
|
|
}
|
|
|
|
// See if we are selecting two values based on a comparison of the two values.
|
|
if (FCmpInst *FCI = dyn_cast<FCmpInst>(CondVal)) {
|
|
if (FCI->getOperand(0) == TrueVal && FCI->getOperand(1) == FalseVal) {
|
|
// Transform (X == Y) ? X : Y -> Y
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
}
|
|
// Transform (X != Y) ? X : Y -> X
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
|
|
return ReplaceInstUsesWith(SI, TrueVal);
|
|
// NOTE: if we wanted to, this is where to detect MIN/MAX
|
|
|
|
} else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
|
|
// Transform (X == Y) ? Y : X -> X
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
|
|
// This is not safe in general for floating point:
|
|
// consider X== -0, Y== +0.
|
|
// It becomes safe if either operand is a nonzero constant.
|
|
ConstantFP *CFPt, *CFPf;
|
|
if (((CFPt = dyn_cast<ConstantFP>(TrueVal)) &&
|
|
!CFPt->getValueAPF().isZero()) ||
|
|
((CFPf = dyn_cast<ConstantFP>(FalseVal)) &&
|
|
!CFPf->getValueAPF().isZero()))
|
|
return ReplaceInstUsesWith(SI, FalseVal);
|
|
}
|
|
// Transform (X != Y) ? Y : X -> Y
|
|
if (FCI->getPredicate() == FCmpInst::FCMP_ONE)
|
|
return ReplaceInstUsesWith(SI, TrueVal);
|
|
// NOTE: if we wanted to, this is where to detect MIN/MAX
|
|
}
|
|
// NOTE: if we wanted to, this is where to detect ABS
|
|
}
|
|
|
|
// See if we are selecting two values based on a comparison of the two values.
|
|
if (ICmpInst *ICI = dyn_cast<ICmpInst>(CondVal))
|
|
if (Instruction *Result = visitSelectInstWithICmp(SI, ICI))
|
|
return Result;
|
|
|
|
if (Instruction *TI = dyn_cast<Instruction>(TrueVal))
|
|
if (Instruction *FI = dyn_cast<Instruction>(FalseVal))
|
|
if (TI->hasOneUse() && FI->hasOneUse()) {
|
|
Instruction *AddOp = 0, *SubOp = 0;
|
|
|
|
// Turn (select C, (op X, Y), (op X, Z)) -> (op X, (select C, Y, Z))
|
|
if (TI->getOpcode() == FI->getOpcode())
|
|
if (Instruction *IV = FoldSelectOpOp(SI, TI, FI))
|
|
return IV;
|
|
|
|
// Turn select C, (X+Y), (X-Y) --> (X+(select C, Y, (-Y))). This is
|
|
// even legal for FP.
|
|
if ((TI->getOpcode() == Instruction::Sub &&
|
|
FI->getOpcode() == Instruction::Add) ||
|
|
(TI->getOpcode() == Instruction::FSub &&
|
|
FI->getOpcode() == Instruction::FAdd)) {
|
|
AddOp = FI; SubOp = TI;
|
|
} else if ((FI->getOpcode() == Instruction::Sub &&
|
|
TI->getOpcode() == Instruction::Add) ||
|
|
(FI->getOpcode() == Instruction::FSub &&
|
|
TI->getOpcode() == Instruction::FAdd)) {
|
|
AddOp = TI; SubOp = FI;
|
|
}
|
|
|
|
if (AddOp) {
|
|
Value *OtherAddOp = 0;
|
|
if (SubOp->getOperand(0) == AddOp->getOperand(0)) {
|
|
OtherAddOp = AddOp->getOperand(1);
|
|
} else if (SubOp->getOperand(0) == AddOp->getOperand(1)) {
|
|
OtherAddOp = AddOp->getOperand(0);
|
|
}
|
|
|
|
if (OtherAddOp) {
|
|
// So at this point we know we have (Y -> OtherAddOp):
|
|
// select C, (add X, Y), (sub X, Z)
|
|
Value *NegVal; // Compute -Z
|
|
if (Constant *C = dyn_cast<Constant>(SubOp->getOperand(1))) {
|
|
NegVal = ConstantExpr::getNeg(C);
|
|
} else {
|
|
NegVal = InsertNewInstBefore(
|
|
BinaryOperator::CreateNeg(SubOp->getOperand(1),
|
|
"tmp"), SI);
|
|
}
|
|
|
|
Value *NewTrueOp = OtherAddOp;
|
|
Value *NewFalseOp = NegVal;
|
|
if (AddOp != TI)
|
|
std::swap(NewTrueOp, NewFalseOp);
|
|
Instruction *NewSel =
|
|
SelectInst::Create(CondVal, NewTrueOp,
|
|
NewFalseOp, SI.getName() + ".p");
|
|
|
|
NewSel = InsertNewInstBefore(NewSel, SI);
|
|
return BinaryOperator::CreateAdd(SubOp->getOperand(0), NewSel);
|
|
}
|
|
}
|
|
}
|
|
|
|
// See if we can fold the select into one of our operands.
|
|
if (SI.getType()->isInteger()) {
|
|
if (Instruction *FoldI = FoldSelectIntoOp(SI, TrueVal, FalseVal))
|
|
return FoldI;
|
|
|
|
// MAX(MAX(a, b), a) -> MAX(a, b)
|
|
// MIN(MIN(a, b), a) -> MIN(a, b)
|
|
// MAX(MIN(a, b), a) -> a
|
|
// MIN(MAX(a, b), a) -> a
|
|
Value *LHS, *RHS, *LHS2, *RHS2;
|
|
if (SelectPatternFlavor SPF = MatchSelectPattern(&SI, LHS, RHS)) {
|
|
if (SelectPatternFlavor SPF2 = MatchSelectPattern(LHS, LHS2, RHS2))
|
|
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
|
|
SI, SPF, RHS))
|
|
return R;
|
|
if (SelectPatternFlavor SPF2 = MatchSelectPattern(RHS, LHS2, RHS2))
|
|
if (Instruction *R = FoldSPFofSPF(cast<Instruction>(RHS),SPF2,LHS2,RHS2,
|
|
SI, SPF, LHS))
|
|
return R;
|
|
}
|
|
|
|
// TODO.
|
|
// ABS(-X) -> ABS(X)
|
|
// ABS(ABS(X)) -> ABS(X)
|
|
}
|
|
|
|
// See if we can fold the select into a phi node if the condition is a select.
|
|
if (isa<PHINode>(SI.getCondition()))
|
|
// The true/false values have to be live in the PHI predecessor's blocks.
|
|
if (CanSelectOperandBeMappingIntoPredBlock(TrueVal, SI) &&
|
|
CanSelectOperandBeMappingIntoPredBlock(FalseVal, SI))
|
|
if (Instruction *NV = FoldOpIntoPhi(SI))
|
|
return NV;
|
|
|
|
if (BinaryOperator::isNot(CondVal)) {
|
|
SI.setOperand(0, BinaryOperator::getNotArgument(CondVal));
|
|
SI.setOperand(1, FalseVal);
|
|
SI.setOperand(2, TrueVal);
|
|
return &SI;
|
|
}
|
|
|
|
return 0;
|
|
}
|