[Mlir-commits] [mlir] mlir/Presburger: contribute a free-standing parser (PR #94916)

[Jay Foad]

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@@ -0,0 +1,67 @@
+//===- Flattener.h - Presburger ParseStruct Flattener -----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_ANALYSIS_PRESBURGER_PARSER_FLATTENER_H
+#define MLIR_ANALYSIS_PRESBURGER_PARSER_FLATTENER_H
+
+#include "ParseStructs.h"
+#include "mlir/Analysis/Presburger/IntegerRelation.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SetVector.h"
+
+namespace mlir::presburger {
+using llvm::SmallDenseMap;
+using llvm::SmallSetVector;
+
+class Flattener : public FinalParseResult {
+public:
+  // The final flattened result is stored here.
+  IntMatrix flatMatrix;
+
+  // We maintain a set of divs that we have seen while flattening. The size of
+  // this set we at most info.numDivs, hitting info.numDivs at the end of the
+  // flattening, if that expression contains all the possible divs.
+  SmallSetVector<size_t, 4> localExprs;
+
+  // We maintain a mapping between local mods and their expansions. The vector
+  // is the dividend.
+  SmallDenseMap<size_t, CoefficientVector, 2> localModExpansion;
+
+  Flattener(FinalParseResult &&parseResult)
+      : FinalParseResult(std::move(parseResult)),
+        flatMatrix(info.numExprs, info.getNumCols()) {}
+
+  std::pair<IntMatrix, IntegerPolyhedron> flatten();
+
+private:
+  void flatten(unsigned row, PureAffineExprImpl &div);
+  void visitDiv(const PureAffineExprImpl &div);
+
+  void addToRow(unsigned row, const CoefficientVector &l) {
+    flatMatrix.addToRow(row,
+                        getDynamicAPIntVec(l.getPadded(info.getNumCols())));
+  }
+  void setRow(unsigned row, const CoefficientVector &l) {
+    flatMatrix.setRow(row, getDynamicAPIntVec(l.getPadded(info.getNumCols())));
+  }
+
+  unsigned lookupLocal(size_t hash) {
+    const auto *it = find(localExprs, hash);
+    assert(it != localExprs.end() &&
+           "Local expression not found; walking from inner to outer?");
+    return info.getLocalVarStartIdx() + it - localExprs.begin();
+  }
+  std::optional<CoefficientVector> lookupModExpansion(size_t hash) {
+    return localModExpansion.contains(hash)
+               ? std::make_optional(localModExpansion.at(hash))
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jayfoad wrote:

I don't think you need the `make_optional`

https://github.com/llvm/llvm-project/pull/94916