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Make ScalarEvolution's GroupByComplexity more thorough. In addition

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to sorting SCEVs by their kind, sort SCEVs of the same kind according
to their operands. This helps avoid things like (a+b) being a distinct
expression from (b+a).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71160 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-05-07 14:39:04 +00:00
parent 6ee2f3d840
commit 72861308d5
1 changed files with 85 additions and 9 deletions
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94
lib/Analysis/ScalarEvolution.cpp
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@ -432,9 +432,84 @@ namespace {
/// SCEVComplexityCompare - Return true if the complexity of the LHS is less
/// than the complexity of the RHS. This comparator is used to canonicalize
/// expressions.
struct VISIBILITY_HIDDEN SCEVComplexityCompare {
class VISIBILITY_HIDDEN SCEVComplexityCompare {
LoopInfo *LI;
public:
explicit SCEVComplexityCompare(LoopInfo *li) : LI(li) {}
bool operator()(const SCEV *LHS, const SCEV *RHS) const {
return LHS->getSCEVType() < RHS->getSCEVType();
// Primarily, sort the SCEVs by their getSCEVType().
if (LHS->getSCEVType() != RHS->getSCEVType())
return LHS->getSCEVType() < RHS->getSCEVType();
// 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)) {
const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
// Compare getValueID values.
if (LU->getValue()->getValueID() != RU->getValue()->getValueID())
return LU->getValue()->getValueID() < RU->getValue()->getValueID();
// Sort arguments by their position.
if (const Argument *LA = dyn_cast<Argument>(LU->getValue())) {
const Argument *RA = cast<Argument>(RU->getValue());
return LA->getArgNo() < RA->getArgNo();
}
// For instructions, compare their loop depth, and their opcode.
// This is pretty loose.
if (Instruction *LV = dyn_cast<Instruction>(LU->getValue())) {
Instruction *RV = cast<Instruction>(RU->getValue());
// Compare loop depths.
if (LI->getLoopDepth(LV->getParent()) !=
LI->getLoopDepth(RV->getParent()))
return LI->getLoopDepth(LV->getParent()) <
LI->getLoopDepth(RV->getParent());
// Compare opcodes.
if (LV->getOpcode() != RV->getOpcode())
return LV->getOpcode() < RV->getOpcode();
// Compare the number of operands.
if (LV->getNumOperands() != RV->getNumOperands())
return LV->getNumOperands() < RV->getNumOperands();
}
return false;
}
// Constant sorting doesn't matter since they'll be folded.
if (isa<SCEVConstant>(LHS))
return false;
// Lexicographically compare n-ary expressions.
if (const SCEVNAryExpr *LC = dyn_cast<SCEVNAryExpr>(LHS)) {
const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
for (unsigned i = 0, e = LC->getNumOperands(); i != e; ++i) {
if (i >= RC->getNumOperands())
return false;
if (operator()(LC->getOperand(i), RC->getOperand(i)))
return true;
if (operator()(RC->getOperand(i), LC->getOperand(i)))
return false;
}
return LC->getNumOperands() < RC->getNumOperands();
}
// Compare cast expressions by operand.
if (const SCEVCastExpr *LC = dyn_cast<SCEVCastExpr>(LHS)) {
const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
return operator()(LC->getOperand(), RC->getOperand());
}
assert(0 && "Unknown SCEV kind!");
return false;
}
};
}
@ -449,18 +524,19 @@ namespace {
/// this to depend on where the addresses of various SCEV objects happened to
/// land in memory.
///
static void GroupByComplexity(std::vector<SCEVHandle> &Ops) {
static void GroupByComplexity(std::vector<SCEVHandle> &Ops,
LoopInfo *LI) {
if (Ops.size() < 2) return; // Noop
if (Ops.size() == 2) {
// This is the common case, which also happens to be trivially simple.
// Special case it.
if (SCEVComplexityCompare()(Ops[1], Ops[0]))
if (SCEVComplexityCompare(LI)(Ops[1], Ops[0]))
std::swap(Ops[0], Ops[1]);
return;
}
// Do the rough sort by complexity.
std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare());
std::stable_sort(Ops.begin(), Ops.end(), SCEVComplexityCompare(LI));
// Now that we are sorted by complexity, group elements of the same
// complexity. Note that this is, at worst, N^2, but the vector is likely to
@ -833,7 +909,7 @@ SCEVHandle ScalarEvolution::getAddExpr(std::vector<SCEVHandle> &Ops) {
if (Ops.size() == 1) return Ops[0];
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
GroupByComplexity(Ops, LI);
// If there are any constants, fold them together.
unsigned Idx = 0;
@ -1058,7 +1134,7 @@ SCEVHandle ScalarEvolution::getMulExpr(std::vector<SCEVHandle> &Ops) {
assert(!Ops.empty() && "Cannot get empty mul!");
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
GroupByComplexity(Ops, LI);
// If there are any constants, fold them together.
unsigned Idx = 0;
@ -1292,7 +1368,7 @@ SCEVHandle ScalarEvolution::getSMaxExpr(std::vector<SCEVHandle> Ops) {
if (Ops.size() == 1) return Ops[0];
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
GroupByComplexity(Ops, LI);
// If there are any constants, fold them together.
unsigned Idx = 0;
@ -1372,7 +1448,7 @@ SCEVHandle ScalarEvolution::getUMaxExpr(std::vector<SCEVHandle> Ops) {
if (Ops.size() == 1) return Ops[0];
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops);
GroupByComplexity(Ops, LI);
// If there are any constants, fold them together.
unsigned Idx = 0;