Summary:
Loop unroll spends a lot of time in SCEVs processing in case when a function
contains hundreds of simple 'for' loops with a quite complex arrays indexes like
for (int i = 0; i < 8; ++i) {
for (int j = 0; j < 32; ++j) {
C[j*8+i] = B[j*32+i+128] + A[i*64+128];
}
}
for (int i = 0; i < 8; ++i) {
for (int j = 0; j < 8; ++j) {
for (int k = 0; k < 32; ++k) {
D[k*64+i*8+j] = D[k*64+i*8+j] + E[i+16] * C[k*8+j+256];
}
}
}
The patch improves loop unroll speed since isLoopBackedgeGuardedByCond takes
much less time than isLoopEntryGuardedByCond in the edge case.
Reviewers: skatkov, sanjoy, mkazantsev
Reviewed By: sanjoy
Subscribers: fhahn, hiraditya, javed.absar, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D72929
!isAvailableAtLoopEntry(SplitRHS.first, MDL))
return false;
- return isLoopEntryGuardedByCond(MDL, Pred, SplitLHS.first, SplitRHS.first) &&
- isLoopBackedgeGuardedByCond(MDL, Pred, SplitLHS.second,
- SplitRHS.second);
+ // It seems backedge guard check is faster than entry one so in some cases
+ // it can speed up whole estimation by short circuit
+ return isLoopBackedgeGuardedByCond(MDL, Pred, SplitLHS.second,
+ SplitRHS.second) &&
+ isLoopEntryGuardedByCond(MDL, Pred, SplitLHS.first, SplitRHS.first);
}
bool ScalarEvolution::isKnownPredicate(ICmpInst::Predicate Pred,