Add FlatAffineConstraints::containsId to avoid using findId when position isn't

needed + other cleanup
- clean up unionBoundingBox (hoist SmallVector allocations out of loop).

PiperOrigin-RevId: 237141668

mlir/include/mlir/Analysis/AffineStructures.h

@@ -436,11 +436,15 @@ public:
   /// constant. Asserts if the 'id' is not found.
   void setIdToConstant(const Value &id, int64_t val);
 
-  /// Looks up the identifier with the specified Value. Returns false if not
-  /// found, true if found. pos is set to the (column) position of the
-  /// identifier.
+  /// Looks up the position of the identifier with the specified Value. Returns
+  /// true if found (false otherwise). `pos' is set to the (column) position of
+  /// the identifier.
   bool findId(const Value &id, unsigned *pos) const;
 
+  /// Returns true if an identifier with the specified Value exists, false
+  /// otherwise.
+  bool containsId(const Value &id) const;
+
   // Add identifiers of the specified kind - specified positions are relative to
   // the kind of identifier. The coefficient column corresponding to the added
   // identifier is initialized to zero. 'id' is the Value corresponding to the

mlir/lib/Analysis/AffineStructures.cpp

@@ -1888,6 +1888,12 @@ bool FlatAffineConstraints::findId(const Value &id, unsigned *pos) const {
   return false;
 }
 
+bool FlatAffineConstraints::containsId(const Value &id) const {
+  return llvm::any_of(ids, [&](const Optional<Value *> &mayBeId) {
+    return mayBeId.hasValue() && mayBeId.getValue() == &id;
+  });
+}
+
 void FlatAffineConstraints::setDimSymbolSeparation(unsigned newSymbolCount) {
   assert(newSymbolCount <= numDims + numSymbols &&
          "invalid separation position");
@@ -2696,19 +2702,21 @@ bool FlatAffineConstraints::unionBoundingBox(
   boundingLbs.reserve(2 * getNumDimIds());
   boundingUbs.reserve(2 * getNumDimIds());
 
-  SmallVector<int64_t, 4> lb, otherLb;
-  lb.reserve(getNumSymbolIds() + 1);
-  otherLb.reserve(getNumSymbolIds() + 1);
+  // To hold lower and upper bounds for each dimension.
+  SmallVector<int64_t, 4> lb, otherLb, ub, otherUb;
+  // To compute min of lower bounds and max of upper bounds for each dimension.
+  SmallVector<int64_t, 4> minLb, maxUb;
+  // To compute final new lower and upper bounds for the union.
+  SmallVector<int64_t, 8> newLb(getNumCols()), newUb(getNumCols());
+
   int64_t lbDivisor, otherLbDivisor;
   for (unsigned d = 0, e = getNumDimIds(); d < e; ++d) {
-    lb.clear();
     auto extent = getConstantBoundOnDimSize(d, &lb, &lbDivisor);
     if (!extent.hasValue())
       // TODO(bondhugula): symbolic extents when necessary.
       // TODO(bondhugula): handle union if a dimension is unbounded.
       return false;
 
-    otherLb.clear();
     auto otherExtent =
         other.getConstantBoundOnDimSize(d, &otherLb, &otherLbDivisor);
     if (!otherExtent.hasValue() || lbDivisor != otherLbDivisor)
@@ -2717,9 +2725,6 @@ bool FlatAffineConstraints::unionBoundingBox(
 
     assert(lbDivisor > 0 && "divisor always expected to be positive");
 
-    // Compute min of lower bounds and max of upper bounds.
-    SmallVector<int64_t, 4> minLb, maxUb;
-
     auto res = compareBounds(lb, otherLb);
     // Identify min.
     if (res == BoundCmpResult::Less || res == BoundCmpResult::Equal) {
@@ -2737,7 +2742,8 @@ bool FlatAffineConstraints::unionBoundingBox(
     }
 
     // Do the same for ub's but max of upper bounds.
-    SmallVector<int64_t, 4> ub(lb), otherUb(otherLb);
+    ub = lb;
+    otherUb = otherLb;
     ub.back() += extent.getValue() - 1;
     otherUb.back() += otherExtent.getValue() - 1;
 
@@ -2757,8 +2763,8 @@ bool FlatAffineConstraints::unionBoundingBox(
       maxUb.back() = std::max(constUb.getValue(), constOtherUb.getValue());
     }
 
-    SmallVector<int64_t, 8> newLb(getNumCols(), 0);
-    SmallVector<int64_t, 8> newUb(getNumCols(), 0);
+    std::fill(newLb.begin(), newLb.end(), 0);
+    std::fill(newUb.begin(), newUb.end(), 0);
 
     // The divisor for lb, ub, otherLb, otherUb at this point is lbDivisor,
     // and so it's the divisor for newLb and newUb as well.

mlir/lib/Analysis/Utils.cpp

@@ -70,9 +70,7 @@ bool ComputationSliceState::getAsConstraints(FlatAffineConstraints *cst) {
   // Add loop bound constraints for values which are loop IVs and equality
   // constraints for symbols which are constants.
   for (const auto &value : values) {
-    unsigned loc;
-    (void)loc;
-    assert(cst->findId(*value, &loc));
+    assert(cst->containsId(*value) && "value expected to be present");
     if (isValidSymbol(value)) {
       // Check if the symbol is a constant.
       if (auto *inst = value->getDefiningInst()) {
@@ -256,8 +254,7 @@ bool MemRefRegion::compute(Instruction *inst, unsigned loopDepth,
   if (sliceState != nullptr) {
     // Add dim and symbol slice operands.
     for (const auto &operand : sliceState->lbOperands[0]) {
-      unsigned loc;
-      if (!cst.findId(*operand, &loc)) {
+      if (!cst.containsId(*operand)) {
         if (isValidSymbol(operand)) {
           cst.addSymbolId(cst.getNumSymbolIds(), const_cast<Value *>(operand));
           // Check if the symbol is a constant.