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[MLIR] Make isPerfectlyNested check more efficient 

Make mlir::isPerfectlyNested more efficient; use O(1) check instead of
O(N) size() method.

Differential Revision: https://reviews.llvm.org/D78428
This commit is contained in:
Uday Bondhugula 2020-04-18 19:07:19 +05:30
parent cacf1b5093
commit f043677f6d
1 changed files with 13 additions and 5 deletions
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18
mlir/lib/Transforms/Utils/LoopUtils.cpp
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@ -705,17 +705,25 @@ bool mlir::isValidLoopInterchangePermutation(ArrayRef<AffineForOp> loops,
return checkLoopInterchangeDependences(depCompsVec, loops, loopPermMap);
}
/// Return true if `loops` is a perfect nest.
/// Returns true if `loops` is a perfectly nested loop nest, where loops appear
/// in it from outermost to innermost.
static bool LLVM_ATTRIBUTE_UNUSED
isPerfectlyNested(ArrayRef<AffineForOp> loops) {
auto outerLoop = loops.front();
assert(!loops.empty() && "no loops provided");
// We already know that the block can't be empty.
auto hasTwoElements = [](Block *block) {
auto secondOpIt = std::next(block->begin());
return secondOpIt != block->end() && &*secondOpIt == &block->back();
};
auto enclosingLoop = loops.front();
for (auto loop : loops.drop_front()) {
auto parentForOp = dyn_cast<AffineForOp>(loop.getParentOp());
// parentForOp's body should be just this loop and the terminator.
if (parentForOp != outerLoop ||
parentForOp.getBody()->getOperations().size() != 2)
if (parentForOp != enclosingLoop || !hasTwoElements(parentForOp.getBody()))
return false;
outerLoop = loop;
enclosingLoop = loop;
}
return true;
}