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[SCEV][NFC] Smarter implementation of isAvailableAtLoopEntry

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isAvailableAtLoopEntry duplicates logic of `properlyDominates` after checking invariance.
This patch replaces this logic with invocation of this method which is more profitable
because it supports caching.

Differential Revision: https://reviews.llvm.org/D43997

llvm-svn: 327373
This commit is contained in:
Max Kazantsev 2018-03-13 07:46:06 +00:00
parent fd88b5baef
commit faa28fa05f
1 changed files with 1 additions and 53 deletions
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54
lib/Analysis/ScalarEvolution.cpp
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@ -2234,59 +2234,7 @@ StrengthenNoWrapFlags(ScalarEvolution *SE, SCEVTypes Type,
}
bool ScalarEvolution::isAvailableAtLoopEntry(const SCEV *S, const Loop *L) {
if (!isLoopInvariant(S, L))
return false;
// If a value depends on a SCEVUnknown which is defined after the loop, we
// conservatively assume that we cannot calculate it at the loop's entry.
struct FindDominatedSCEVUnknown {
bool Found = false;
const Loop *L;
DominatorTree &DT;
LoopInfo &LI;
FindDominatedSCEVUnknown(const Loop *L, DominatorTree &DT, LoopInfo &LI)
: L(L), DT(DT), LI(LI) {}
bool checkSCEVUnknown(const SCEVUnknown *SU) {
if (auto *I = dyn_cast<Instruction>(SU->getValue())) {
if (DT.dominates(L->getHeader(), I->getParent()))
Found = true;
else
assert(DT.dominates(I->getParent(), L->getHeader()) &&
"No dominance relationship between SCEV and loop?");
}
return false;
}
bool follow(const SCEV *S) {
switch (static_cast<SCEVTypes>(S->getSCEVType())) {
case scConstant:
return false;
case scAddRecExpr:
case scTruncate:
case scZeroExtend:
case scSignExtend:
case scAddExpr:
case scMulExpr:
case scUMaxExpr:
case scSMaxExpr:
case scUDivExpr:
return true;
case scUnknown:
return checkSCEVUnknown(cast<SCEVUnknown>(S));
case scCouldNotCompute:
llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!");
}
return false;
}
bool isDone() { return Found; }
};
FindDominatedSCEVUnknown FSU(L, DT, LI);
SCEVTraversal<FindDominatedSCEVUnknown> ST(FSU);
ST.visitAll(S);
return !FSU.Found;
return isLoopInvariant(S, L) && properlyDominates(S, L->getHeader());
}
/// Get a canonical add expression, or something simpler if possible.