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Optimize ScalarEvolution's SCEVComplexityCompare predicate: don't go

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scrounging through SCEVUnknown contents and SCEVNAryExpr operands;
instead just do a simple deterministic comparison of the precomputed
hash data.

Also, since this is more precise, it eliminates the need for the slow
N^2 duplicate detection code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@105540 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-06-07 19:06:13 +00:00
parent 22a5b29820
commit 4d52c6d622
3 changed files with 18 additions and 124 deletions
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3
include/llvm/Analysis/ScalarEvolution.h
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@ -76,6 +76,9 @@ namespace llvm {
/// Profile - FoldingSet support.
void Profile(FoldingSetNodeID& ID) { ID = FastID; }
/// getProfile - Like Profile, but a different interface which doesn't copy.
const FoldingSetNodeIDRef &getProfile() const { return FastID; }
/// isLoopInvariant - Return true if the value of this SCEV is unchanging in
/// the specified loop.
virtual bool isLoopInvariant(const Loop *L) const = 0;

137
lib/Analysis/ScalarEvolution.cpp
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@ -508,106 +508,15 @@ namespace {
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);
// Order pointer values after integer values. This helps SCEVExpander
// form GEPs.
if (LU->getType()->isPointerTy() && !RU->getType()->isPointerTy())
return false;
if (RU->getType()->isPointerTy() && !LU->getType()->isPointerTy())
return true;
// 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;
}
// Compare constant values.
if (const SCEVConstant *LC = dyn_cast<SCEVConstant>(LHS)) {
const SCEVConstant *RC = cast<SCEVConstant>(RHS);
if (LC->getValue()->getBitWidth() != RC->getValue()->getBitWidth())
return LC->getValue()->getBitWidth() < RC->getValue()->getBitWidth();
return LC->getValue()->getValue().ult(RC->getValue()->getValue());
}
// Compare addrec loop depths.
if (const SCEVAddRecExpr *LA = dyn_cast<SCEVAddRecExpr>(LHS)) {
const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
if (LA->getLoop()->getLoopDepth() != RA->getLoop()->getLoopDepth())
return LA->getLoop()->getLoopDepth() < RA->getLoop()->getLoopDepth();
}
// 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();
}
// Lexicographically compare udiv expressions.
if (const SCEVUDivExpr *LC = dyn_cast<SCEVUDivExpr>(LHS)) {
const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
if (operator()(LC->getLHS(), RC->getLHS()))
return true;
if (operator()(RC->getLHS(), LC->getLHS()))
return false;
if (operator()(LC->getRHS(), RC->getRHS()))
return true;
if (operator()(RC->getRHS(), LC->getRHS()))
return false;
return false;
}
// 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());
}
llvm_unreachable("Unknown SCEV kind!");
return false;
// Then, pick an arbitrary sort. Use the profiling data for speed.
const FoldingSetNodeIDRef &L = LHS->getProfile();
const FoldingSetNodeIDRef &R = RHS->getProfile();
size_t LSize = L.getSize();
size_t RSize = R.getSize();
if (LSize != RSize)
return LSize < RSize;
return memcmp(L.getData(), R.getData(),
LSize * sizeof(*L.getData())) < 0;
}
};
}
@ -625,36 +534,18 @@ namespace {
static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
LoopInfo *LI) {
if (Ops.size() < 2) return; // Noop
SCEVComplexityCompare Comp(LI);
if (Ops.size() == 2) {
// This is the common case, which also happens to be trivially simple.
// Special case it.
if (SCEVComplexityCompare(LI)(Ops[1], Ops[0]))
if (Comp(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(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
// be extremely short in practice. Note that we take this approach because we
// do not want to depend on the addresses of the objects we are grouping.
for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
const SCEV *S = Ops[i];
unsigned Complexity = S->getSCEVType();
// If there are any objects of the same complexity and same value as this
// one, group them.
for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
if (Ops[j] == S) { // Found a duplicate.
// Move it to immediately after i'th element.
std::swap(Ops[i+1], Ops[j]);
++i; // no need to rescan it.
if (i == e-2) return; // Done!
}
}
}
std::stable_sort(Ops.begin(), Ops.end(), Comp);
}

2
test/Analysis/ScalarEvolution/2008-07-29-SMinExpr.ll
View File

@ -22,5 +22,5 @@ afterfor: ; preds = %forinc, %entry
ret i32 %j.0.lcssa
}
; CHECK: backedge-taken count is (-2147483632 + ((-1 + (-1 * %x)) smax (-1 + (-1 * %y))))
; CHECK: backedge-taken count is (-2147483632 + ((-1 + (-1 * %y)) smax (-1 + (-1 * %x))))