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[SCEV] Refactor out a createNodeForSelect
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Summary:
We will shortly re-use this for select-like br-phi pairs.

Reviewers: atrick, joker-eph, joker.eph

Subscribers: sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D13377

llvm-svn: 249177
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@sanjoy
sanjoy committed Oct 2, 2015
1 parent d4c5fb5 commit d067134
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Showing 2 changed files with 107 additions and 88 deletions.
7 changes: 7 additions & 0 deletions llvm/include/llvm/Analysis/ScalarEvolution.h
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Original file line number Diff line number Diff line change
Expand Up @@ -415,6 +415,13 @@ namespace llvm {
/// Provide the special handling we need to analyze PHI SCEVs.
const SCEV *createNodeForPHI(PHINode *PN);

/// Provide special handling for a select-like instruction (currently this
/// is either a select instruction or a phi node). \p I is the instruction
/// being processed, and it is assumed equivalent to "Cond ? TrueVal :
/// FalseVal".
const SCEV *createNodeForSelect(Instruction *I, Value *Cond, Value *TrueVal,
Value *FalseVal);

/// Provide the special handling we need to analyze GEP SCEVs.
const SCEV *createNodeForGEP(GEPOperator *GEP);

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188 changes: 100 additions & 88 deletions llvm/lib/Analysis/ScalarEvolution.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3756,6 +3756,99 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
return getUnknown(PN);
}

const SCEV *ScalarEvolution::createNodeForSelect(Instruction *I, Value *Cond,
Value *TrueVal,
Value *FalseVal) {
// Try to match some simple smax or umax patterns.
auto *ICI = dyn_cast<ICmpInst>(Cond);
if (!ICI)
return getUnknown(I);

Value *LHS = ICI->getOperand(0);
Value *RHS = ICI->getOperand(1);

switch (ICI->getPredicate()) {
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE:
std::swap(LHS, RHS);
// fall through
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE:
// a >s b ? a+x : b+x -> smax(a, b)+x
// a >s b ? b+x : a+x -> smin(a, b)+x
if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
const SCEV *LS = getNoopOrSignExtend(getSCEV(LHS), I->getType());
const SCEV *RS = getNoopOrSignExtend(getSCEV(RHS), I->getType());
const SCEV *LA = getSCEV(TrueVal);
const SCEV *RA = getSCEV(FalseVal);
const SCEV *LDiff = getMinusSCEV(LA, LS);
const SCEV *RDiff = getMinusSCEV(RA, RS);
if (LDiff == RDiff)
return getAddExpr(getSMaxExpr(LS, RS), LDiff);
LDiff = getMinusSCEV(LA, RS);
RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getSMinExpr(LS, RS), LDiff);
}
break;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE:
std::swap(LHS, RHS);
// fall through
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE:
// a >u b ? a+x : b+x -> umax(a, b)+x
// a >u b ? b+x : a+x -> umin(a, b)+x
if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
const SCEV *RS = getNoopOrZeroExtend(getSCEV(RHS), I->getType());
const SCEV *LA = getSCEV(TrueVal);
const SCEV *RA = getSCEV(FalseVal);
const SCEV *LDiff = getMinusSCEV(LA, LS);
const SCEV *RDiff = getMinusSCEV(RA, RS);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(LS, RS), LDiff);
LDiff = getMinusSCEV(LA, RS);
RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getUMinExpr(LS, RS), LDiff);
}
break;
case ICmpInst::ICMP_NE:
// n != 0 ? n+x : 1+x -> umax(n, 1)+x
if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
const SCEV *One = getOne(I->getType());
const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
const SCEV *LA = getSCEV(TrueVal);
const SCEV *RA = getSCEV(FalseVal);
const SCEV *LDiff = getMinusSCEV(LA, LS);
const SCEV *RDiff = getMinusSCEV(RA, One);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(One, LS), LDiff);
}
break;
case ICmpInst::ICMP_EQ:
// n == 0 ? 1+x : n+x -> umax(n, 1)+x
if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
const SCEV *One = getOne(I->getType());
const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
const SCEV *LA = getSCEV(TrueVal);
const SCEV *RA = getSCEV(FalseVal);
const SCEV *LDiff = getMinusSCEV(LA, One);
const SCEV *RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(One, LS), LDiff);
}
break;
default:
break;
}

return getUnknown(I);
}

/// createNodeForGEP - Expand GEP instructions into add and multiply
/// operations. This allows them to be analyzed by regular SCEV code.
///
Expand Down Expand Up @@ -4470,94 +4563,13 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
return createNodeForPHI(cast<PHINode>(U));

case Instruction::Select:
// This could be a smax or umax that was lowered earlier.
// Try to recover it.
if (ICmpInst *ICI = dyn_cast<ICmpInst>(U->getOperand(0))) {
Value *LHS = ICI->getOperand(0);
Value *RHS = ICI->getOperand(1);
switch (ICI->getPredicate()) {
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE:
std::swap(LHS, RHS);
// fall through
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE:
// a >s b ? a+x : b+x -> smax(a, b)+x
// a >s b ? b+x : a+x -> smin(a, b)+x
if (getTypeSizeInBits(LHS->getType()) <=
getTypeSizeInBits(U->getType())) {
const SCEV *LS = getNoopOrSignExtend(getSCEV(LHS), U->getType());
const SCEV *RS = getNoopOrSignExtend(getSCEV(RHS), U->getType());
const SCEV *LA = getSCEV(U->getOperand(1));
const SCEV *RA = getSCEV(U->getOperand(2));
const SCEV *LDiff = getMinusSCEV(LA, LS);
const SCEV *RDiff = getMinusSCEV(RA, RS);
if (LDiff == RDiff)
return getAddExpr(getSMaxExpr(LS, RS), LDiff);
LDiff = getMinusSCEV(LA, RS);
RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getSMinExpr(LS, RS), LDiff);
}
break;
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE:
std::swap(LHS, RHS);
// fall through
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE:
// a >u b ? a+x : b+x -> umax(a, b)+x
// a >u b ? b+x : a+x -> umin(a, b)+x
if (getTypeSizeInBits(LHS->getType()) <=
getTypeSizeInBits(U->getType())) {
const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), U->getType());
const SCEV *RS = getNoopOrZeroExtend(getSCEV(RHS), U->getType());
const SCEV *LA = getSCEV(U->getOperand(1));
const SCEV *RA = getSCEV(U->getOperand(2));
const SCEV *LDiff = getMinusSCEV(LA, LS);
const SCEV *RDiff = getMinusSCEV(RA, RS);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(LS, RS), LDiff);
LDiff = getMinusSCEV(LA, RS);
RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getUMinExpr(LS, RS), LDiff);
}
break;
case ICmpInst::ICMP_NE:
// n != 0 ? n+x : 1+x -> umax(n, 1)+x
if (getTypeSizeInBits(LHS->getType()) <=
getTypeSizeInBits(U->getType()) &&
isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
const SCEV *One = getOne(U->getType());
const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), U->getType());
const SCEV *LA = getSCEV(U->getOperand(1));
const SCEV *RA = getSCEV(U->getOperand(2));
const SCEV *LDiff = getMinusSCEV(LA, LS);
const SCEV *RDiff = getMinusSCEV(RA, One);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(One, LS), LDiff);
}
break;
case ICmpInst::ICMP_EQ:
// n == 0 ? 1+x : n+x -> umax(n, 1)+x
if (getTypeSizeInBits(LHS->getType()) <=
getTypeSizeInBits(U->getType()) &&
isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
const SCEV *One = getOne(U->getType());
const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), U->getType());
const SCEV *LA = getSCEV(U->getOperand(1));
const SCEV *RA = getSCEV(U->getOperand(2));
const SCEV *LDiff = getMinusSCEV(LA, One);
const SCEV *RDiff = getMinusSCEV(RA, LS);
if (LDiff == RDiff)
return getAddExpr(getUMaxExpr(One, LS), LDiff);
}
break;
default:
break;
}
}
// U can also be a select constant expr, which let fall through. Since
// createNodeForSelect only works for a condition that is an `ICmpInst`, and
// constant expressions cannot have instructions as operands, we'd have
// returned getUnknown for a select constant expressions anyway.
if (isa<Instruction>(U))
return createNodeForSelect(cast<Instruction>(U), U->getOperand(0),
U->getOperand(1), U->getOperand(2));

default: // We cannot analyze this expression.
break;
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