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[SCEV] Avoid unnecessary domination checks (NFC) 

When determining the defining scope, avoid repeatedly querying
dominationg against the function entry instruction. This ends up
begin a very common case that we can handle more efficiently.
This commit is contained in:
Nikita Popov 2021-10-05 23:21:25 +02:00
parent 62d67d9e7c
commit 17c20a6dfb
2 changed files with 12 additions and 12 deletions
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5
llvm/include/llvm/Analysis/ScalarEvolution.h
View File

@ -1921,9 +1921,10 @@ private:
SCEV::NoWrapFlags getNoWrapFlagsFromUB(const Value *V);
/// Return a scope which provides an upper bound on the defining scope of
/// 'S'. Specifically, return the first instruction in said bounding scope.
/// 'S'. Specifically, return the first instruction in said bounding scope.
/// Return nullptr if the scope is trivial (function entry).
/// (See scope definition rules associated with flag discussion above)
const Instruction *getDefiningScopeBound(const SCEV *S);
const Instruction *getNonTrivialDefiningScopeBound(const SCEV *S);
/// Return a scope which provides an upper bound on the defining scope for
/// a SCEV with the operands in Ops.

19
llvm/lib/Analysis/ScalarEvolution.cpp
View File

@ -6585,25 +6585,24 @@ SCEV::NoWrapFlags ScalarEvolution::getNoWrapFlagsFromUB(const Value *V) {
return isSCEVExprNeverPoison(BinOp) ? Flags : SCEV::FlagAnyWrap;
}
const Instruction *ScalarEvolution::getDefiningScopeBound(const SCEV *S) {
const Instruction *
ScalarEvolution::getNonTrivialDefiningScopeBound(const SCEV *S) {
if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(S))
return &*AddRec->getLoop()->getHeader()->begin();
if (auto *U = dyn_cast<SCEVUnknown>(S))
if (auto *I = dyn_cast<Instruction>(U->getValue()))
return I;
// All SCEVs are bound by the entry to F
return &*F.getEntryBlock().begin();
return nullptr;
}
const Instruction *
ScalarEvolution::getDefiningScopeBound(ArrayRef<const SCEV *> Ops) {
const Instruction *Bound = &*F.getEntryBlock().begin();
for (auto *S : Ops) {
auto *DefI = getDefiningScopeBound(S);
if (DT.dominates(Bound, DefI))
Bound = DefI;
}
return Bound;
const Instruction *Bound = nullptr;
for (auto *S : Ops)
if (auto *DefI = getNonTrivialDefiningScopeBound(S))
if (!Bound || DT.dominates(Bound, DefI))
Bound = DefI;
return Bound ? Bound : &*F.getEntryBlock().begin();
}