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Optimize SCEVComplexityCompare. Use a 3-way return instead of a 2-way 

return to avoid needing two calls to test for equivalence, and sort
addrecs by their degree before examining their operands.

llvm-svn: 112267
This commit is contained in:
Dan Gohman 2010-08-27 15:26:01 +00:00
parent ca15841394
commit 2706567c5c
1 changed files with 82 additions and 48 deletions
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130
llvm/lib/Analysis/ScalarEvolution.cpp
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@ -523,24 +523,34 @@ namespace {
public:
explicit SCEVComplexityCompare(const LoopInfo *li) : LI(li) {}
// Return true or false if LHS is less than, or at least RHS, respectively.
bool operator()(const SCEV *LHS, const SCEV *RHS) const {
return compare(LHS, RHS) < 0;
}
// Return negative, zero, or positive, if LHS is less than, equal to, or
// greater than RHS, respectively. A three-way result allows recursive
// comparisons to be more efficient.
int compare(const SCEV *LHS, const SCEV *RHS) const {
// Fast-path: SCEVs are uniqued so we can do a quick equality check.
if (LHS == RHS)
return false;
return 0;
// Primarily, sort the SCEVs by their getSCEVType().
unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
if (LType != RType)
return LType < RType;
return (int)LType - (int)RType;
// Aside from the getSCEVType() ordering, the particular ordering
// isn't very important except that it's beneficial to be consistent,
// so that (a + b) and (b + a) don't end up as different expressions.
// Sort SCEVUnknown values with some loose heuristics. TODO: This is
// not as complete as it could be.
if (const SCEVUnknown *LU = dyn_cast<SCEVUnknown>(LHS)) {
switch (LType) {
case scUnknown: {
const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
// Sort SCEVUnknown values with some loose heuristics. TODO: This is
// not as complete as it could be.
const Value *LV = LU->getValue(), *RV = RU->getValue();
// Order pointer values after integer values. This helps SCEVExpander
@ -548,22 +558,23 @@ namespace {
bool LIsPointer = LV->getType()->isPointerTy(),
RIsPointer = RV->getType()->isPointerTy();
if (LIsPointer != RIsPointer)
return RIsPointer;
return (int)LIsPointer - (int)RIsPointer;
// Compare getValueID values.
unsigned LID = LV->getValueID(),
RID = RV->getValueID();
if (LID != RID)
return LID < RID;
return (int)LID - (int)RID;
// Sort arguments by their position.
if (const Argument *LA = dyn_cast<Argument>(LV)) {
const Argument *RA = cast<Argument>(RV);
return LA->getArgNo() < RA->getArgNo();
unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
return (int)LArgNo - (int)RArgNo;
}
// For instructions, compare their loop depth, and their opcode.
// This is pretty loose.
// For instructions, compare their loop depth, and their operand
// count. This is pretty loose.
if (const Instruction *LInst = dyn_cast<Instruction>(LV)) {
const Instruction *RInst = cast<Instruction>(RV);
@ -574,82 +585,105 @@ namespace {
unsigned LDepth = LI->getLoopDepth(LParent),
RDepth = LI->getLoopDepth(RParent);
if (LDepth != RDepth)
return LDepth < RDepth;
return (int)LDepth - (int)RDepth;
}
// Compare the number of operands.
unsigned LNumOps = LInst->getNumOperands(),
RNumOps = RInst->getNumOperands();
if (LNumOps != RNumOps)
return LNumOps < RNumOps;
return (int)LNumOps - (int)RNumOps;
}
return false;
return 0;
}
// Compare constant values.
if (const SCEVConstant *LC = dyn_cast<SCEVConstant>(LHS)) {
case scConstant: {
const SCEVConstant *LC = cast<SCEVConstant>(LHS);
const SCEVConstant *RC = cast<SCEVConstant>(RHS);
// Compare constant values.
const APInt &LA = LC->getValue()->getValue();
const APInt &RA = RC->getValue()->getValue();
unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
if (LBitWidth != RBitWidth)
return LBitWidth < RBitWidth;
return LA.ult(RA);
return (int)LBitWidth - (int)RBitWidth;
return LA.ult(RA) ? -1 : 1;
}
// Compare addrec loop depths.
if (const SCEVAddRecExpr *LA = dyn_cast<SCEVAddRecExpr>(LHS)) {
case scAddRecExpr: {
const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
// Compare addrec loop depths.
const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
if (LLoop != RLoop) {
unsigned LDepth = LLoop->getLoopDepth(),
RDepth = RLoop->getLoopDepth();
if (LDepth != RDepth)
return LDepth < RDepth;
return (int)LDepth - (int)RDepth;
}
// Addrec complexity grows with operand count.
unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
if (LNumOps != RNumOps)
return (int)LNumOps - (int)RNumOps;
// Lexicographically compare.
for (unsigned i = 0; i != LNumOps; ++i) {
long X = compare(LA->getOperand(i), RA->getOperand(i));
if (X != 0)
return X;
}
return 0;
}
// Lexicographically compare n-ary expressions.
if (const SCEVNAryExpr *LC = dyn_cast<SCEVNAryExpr>(LHS)) {
case scAddExpr:
case scMulExpr:
case scSMaxExpr:
case scUMaxExpr: {
const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
// Lexicographically compare n-ary expressions.
unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
for (unsigned i = 0; i != LNumOps; ++i) {
if (i >= RNumOps)
return false;
const SCEV *LOp = LC->getOperand(i), *ROp = RC->getOperand(i);
if (operator()(LOp, ROp))
return true;
if (operator()(ROp, LOp))
return false;
return 1;
long X = compare(LC->getOperand(i), RC->getOperand(i));
if (X != 0)
return X;
}
return LNumOps < RNumOps;
return (int)LNumOps - (int)RNumOps;
}
// Lexicographically compare udiv expressions.
if (const SCEVUDivExpr *LC = dyn_cast<SCEVUDivExpr>(LHS)) {
case scUDivExpr: {
const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
const SCEV *LL = LC->getLHS(), *LR = LC->getRHS(),
*RL = RC->getLHS(), *RR = RC->getRHS();
if (operator()(LL, RL))
return true;
if (operator()(RL, LL))
return false;
if (operator()(LR, RR))
return true;
if (operator()(RR, LR))
return false;
return false;
// Lexicographically compare udiv expressions.
long X = compare(LC->getLHS(), RC->getLHS());
if (X != 0)
return X;
return compare(LC->getRHS(), RC->getRHS());
}
// Compare cast expressions by operand.
if (const SCEVCastExpr *LC = dyn_cast<SCEVCastExpr>(LHS)) {
case scTruncate:
case scZeroExtend:
case scSignExtend: {
const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
return operator()(LC->getOperand(), RC->getOperand());
// Compare cast expressions by operand.
return compare(LC->getOperand(), RC->getOperand());
}
default:
break;
}
llvm_unreachable("Unknown SCEV kind!");
return false;
return 0;
}
};
}