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[MLIR] Add debug support for ignored patterns 

The rewrite engine's cost model may determine some patterns to be irrelevant
ahead of their application. These patterns were silently ignored previously and
now cause a message in `--debug` mode.

Differential Revision: https://reviews.llvm.org/D87290
This commit is contained in:
Frederik Gossen 2020-09-09 07:16:45 +00:00
parent 2a52c3301a
commit 6a494e117c
1 changed files with 24 additions and 3 deletions
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27
mlir/lib/IR/PatternMatch.cpp
View File

@ -10,9 +10,12 @@
#include "mlir/IR/BlockAndValueMapping.h"
#include "mlir/IR/Operation.h"
#include "mlir/IR/Value.h"
#include "llvm/Support/Debug.h"
using namespace mlir;
#define DEBUG_TYPE "pattern-match"
PatternBenefit::PatternBenefit(unsigned benefit) : representation(benefit) {
assert(representation == benefit && benefit != ImpossibleToMatchSentinel &&
"This pattern match benefit is too large to represent");
@ -207,8 +210,14 @@ void PatternApplicator::applyCostModel(CostModel model) {
anyOpPatterns.clear();
for (const auto &pat : owningPatternList) {
// If the pattern is always impossible to match, just ignore it.
if (pat->getBenefit().isImpossibleToMatch())
if (pat->getBenefit().isImpossibleToMatch()) {
LLVM_DEBUG({
llvm::dbgs()
<< "Ignoring pattern '" << pat->getRootKind()
<< "' because it is impossible to match (by pattern benefit)\n";
});
continue;
}
if (Optional<OperationName> opName = pat->getRootKind())
patterns[*opName].push_back(pat.get());
else
@ -223,8 +232,14 @@ void PatternApplicator::applyCostModel(CostModel model) {
auto processPatternList = [&](SmallVectorImpl<RewritePattern *> &list) {
// Special case for one pattern in the list, which is the most common case.
if (list.size() == 1) {
if (model(*list.front()).isImpossibleToMatch())
if (model(*list.front()).isImpossibleToMatch()) {
LLVM_DEBUG({
llvm::dbgs() << "Ignoring pattern '" << list.front()->getRootKind()
<< "' because it is impossible to match or cannot lead "
"to legal IR (by cost model)\n";
});
list.clear();
}
return;
}
@ -236,8 +251,14 @@ void PatternApplicator::applyCostModel(CostModel model) {
// Sort patterns with highest benefit first, and remove those that are
// impossible to match.
std::stable_sort(list.begin(), list.end(), cmp);
while (!list.empty() && benefits[list.back()].isImpossibleToMatch())
while (!list.empty() && benefits[list.back()].isImpossibleToMatch()) {
LLVM_DEBUG({
llvm::dbgs() << "Ignoring pattern '" << list.back()->getRootKind()
<< "' because it is impossible to match or cannot lead to "
"legal IR (by cost model)\n";
});
list.pop_back();
}
};
for (auto &it : patterns)
processPatternList(it.second);