[MLIR][Presburger] Implement PresburgerSpace::mergeAndAlignSymbols (#76397)

Author: iambrj

mlir/include/mlir/Analysis/Presburger/PresburgerSpace.h

@@ -290,6 +290,11 @@ class PresburgerSpace {
   /// the symbols in two spaces are aligned.
   bool isAligned(const PresburgerSpace &other, VarKind kind) const;
 
+  /// Merge and align symbol variables of `this` and `other` with respect to
+  /// identifiers. After this operation the symbol variables of both spaces have
+  /// the same identifiers in the same order.
+  void mergeAndAlignSymbols(PresburgerSpace &other);
+
   void print(llvm::raw_ostream &os) const;
   void dump() const;
 

mlir/lib/Analysis/Presburger/PresburgerSpace.cpp

@@ -294,6 +294,40 @@ void PresburgerSpace::setVarSymbolSeperation(unsigned newSymbolCount) {
   // `identifiers` remains same.
 }
 
+void PresburgerSpace::mergeAndAlignSymbols(PresburgerSpace &other) {
+  assert(usingIds && other.usingIds &&
+         "Both spaces need to have identifers to merge & align");
+
+  // First merge & align identifiers into `other` from `this`.
+  unsigned kindBeginOffset = other.getVarKindOffset(VarKind::Symbol);
+  unsigned i = 0;
+  for (const Identifier *identifier =
+           identifiers.begin() + getVarKindOffset(VarKind::Symbol);
+       identifier != identifiers.begin() + getVarKindEnd(VarKind::Symbol);
+       identifier++) {
+    // If the identifier exists in `other`, then align it; otherwise insert it
+    // assuming it is a new identifier. Search in `other` starting at position
+    // `i` since the left of `i` is aligned.
+    auto *findEnd =
+        other.identifiers.begin() + other.getVarKindEnd(VarKind::Symbol);
+    auto *itr = std::find(other.identifiers.begin() + kindBeginOffset + i,
+                          findEnd, *identifier);
+    if (itr != findEnd) {
+      std::iter_swap(other.identifiers.begin() + kindBeginOffset + i, itr);
+    } else {
+      other.insertVar(VarKind::Symbol, i);
+      other.getId(VarKind::Symbol, i) = *identifier;
+    }
+    i++;
+  }
+
+  // Finally add identifiers that are in `other`, but not in `this` to `this`.
+  for (unsigned e = other.getNumVarKind(VarKind::Symbol); i < e; i++) {
+    insertVar(VarKind::Symbol, i);
+    getId(VarKind::Symbol, i) = other.getId(VarKind::Symbol, i);
+  }
+}
+
 void PresburgerSpace::print(llvm::raw_ostream &os) const {
   os << "Domain: " << getNumDomainVars() << ", "
      << "Range: " << getNumRangeVars() << ", "

mlir/unittests/Analysis/Presburger/PresburgerSpaceTest.cpp

@@ -193,3 +193,73 @@ TEST(PresburgerSpaceTest, convertVarKind2) {
   EXPECT_EQ(space.getId(VarKind::Symbol, 2), Identifier(&identifiers[1]));
   EXPECT_EQ(space.getId(VarKind::Symbol, 3), Identifier(&identifiers[3]));
 }
+
+TEST(PresburgerSpaceTest, mergeAndAlignSymbols) {
+  PresburgerSpace space = PresburgerSpace::getRelationSpace(3, 3, 2, 0);
+  space.resetIds();
+
+  PresburgerSpace otherSpace = PresburgerSpace::getRelationSpace(3, 2, 3, 0);
+  otherSpace.resetIds();
+
+  // Attach identifiers.
+  int identifiers[7] = {0, 1, 2, 3, 4, 5, 6};
+  int otherIdentifiers[8] = {10, 11, 12, 13, 14, 15, 16, 17};
+
+  space.getId(VarKind::Domain, 0) = Identifier(&identifiers[0]);
+  space.getId(VarKind::Domain, 1) = Identifier(&identifiers[1]);
+  // Note the common identifier.
+  space.getId(VarKind::Domain, 2) = Identifier(&otherIdentifiers[2]);
+  space.getId(VarKind::Range, 0) = Identifier(&identifiers[2]);
+  space.getId(VarKind::Range, 1) = Identifier(&identifiers[3]);
+  space.getId(VarKind::Range, 2) = Identifier(&identifiers[4]);
+  space.getId(VarKind::Symbol, 0) = Identifier(&identifiers[5]);
+  space.getId(VarKind::Symbol, 1) = Identifier(&identifiers[6]);
+
+  otherSpace.getId(VarKind::Domain, 0) = Identifier(&otherIdentifiers[0]);
+  otherSpace.getId(VarKind::Domain, 1) = Identifier(&otherIdentifiers[1]);
+  otherSpace.getId(VarKind::Domain, 2) = Identifier(&otherIdentifiers[2]);
+  otherSpace.getId(VarKind::Range, 0) = Identifier(&otherIdentifiers[3]);
+  otherSpace.getId(VarKind::Range, 1) = Identifier(&otherIdentifiers[4]);
+  // Note the common identifier.
+  otherSpace.getId(VarKind::Symbol, 0) = Identifier(&identifiers[6]);
+  otherSpace.getId(VarKind::Symbol, 1) = Identifier(&otherIdentifiers[5]);
+  otherSpace.getId(VarKind::Symbol, 2) = Identifier(&otherIdentifiers[7]);
+
+  space.mergeAndAlignSymbols(otherSpace);
+
+  // Check if merge & align is successful.
+  // Check symbol var identifiers.
+  EXPECT_EQ(4u, space.getNumSymbolVars());
+  EXPECT_EQ(4u, otherSpace.getNumSymbolVars());
+  EXPECT_EQ(space.getId(VarKind::Symbol, 0), Identifier(&identifiers[5]));
+  EXPECT_EQ(space.getId(VarKind::Symbol, 1), Identifier(&identifiers[6]));
+  EXPECT_EQ(space.getId(VarKind::Symbol, 2), Identifier(&otherIdentifiers[5]));
+  EXPECT_EQ(space.getId(VarKind::Symbol, 3), Identifier(&otherIdentifiers[7]));
+  EXPECT_EQ(otherSpace.getId(VarKind::Symbol, 0), Identifier(&identifiers[5]));
+  EXPECT_EQ(otherSpace.getId(VarKind::Symbol, 1), Identifier(&identifiers[6]));
+  EXPECT_EQ(otherSpace.getId(VarKind::Symbol, 2),
+            Identifier(&otherIdentifiers[5]));
+  EXPECT_EQ(otherSpace.getId(VarKind::Symbol, 3),
+            Identifier(&otherIdentifiers[7]));
+  // Check that domain and range var identifiers are not affected.
+  EXPECT_EQ(3u, space.getNumDomainVars());
+  EXPECT_EQ(3u, space.getNumRangeVars());
+  EXPECT_EQ(space.getId(VarKind::Domain, 0), Identifier(&identifiers[0]));
+  EXPECT_EQ(space.getId(VarKind::Domain, 1), Identifier(&identifiers[1]));
+  EXPECT_EQ(space.getId(VarKind::Domain, 2), Identifier(&otherIdentifiers[2]));
+  EXPECT_EQ(space.getId(VarKind::Range, 0), Identifier(&identifiers[2]));
+  EXPECT_EQ(space.getId(VarKind::Range, 1), Identifier(&identifiers[3]));
+  EXPECT_EQ(space.getId(VarKind::Range, 2), Identifier(&identifiers[4]));
+  EXPECT_EQ(3u, otherSpace.getNumDomainVars());
+  EXPECT_EQ(2u, otherSpace.getNumRangeVars());
+  EXPECT_EQ(otherSpace.getId(VarKind::Domain, 0),
+            Identifier(&otherIdentifiers[0]));
+  EXPECT_EQ(otherSpace.getId(VarKind::Domain, 1),
+            Identifier(&otherIdentifiers[1]));
+  EXPECT_EQ(otherSpace.getId(VarKind::Domain, 2),
+            Identifier(&otherIdentifiers[2]));
+  EXPECT_EQ(otherSpace.getId(VarKind::Range, 0),
+            Identifier(&otherIdentifiers[3]));
+  EXPECT_EQ(otherSpace.getId(VarKind::Range, 1),
+            Identifier(&otherIdentifiers[4]));
+}