[Mlir-commits] [mlir] [mlir][affine] Use value bound inference to determine minimum/maximum trip counts in loop analysis (PR #128113)

[lonely eagle]

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@@ -212,6 +214,40 @@ void mlir::affine::getTripCountMapAndOperands(
                             tripCountValueMap.getOperands().end());
 }
 
+/// Take the min if all trip counts are constant.
+static std::optional<uint64_t>
+getKnownTripCountBound(AffineMap map, SmallVectorImpl<Value> &operands,
+                       presburger::BoundType type) {
+  std::optional<uint64_t> tripCount;
+  for (auto resultExpr : map.getResults()) {
+    AffineMap subMap =
+        AffineMap::get(map.getNumDims(), map.getNumSymbols(), resultExpr);
+    ValueBoundsConstraintSet::Variable var(subMap, operands);
+    auto lbBound = ValueBoundsConstraintSet::computeConstantBound(
+        mlir::presburger::BoundType::LB, var);
+    auto ubBound = ValueBoundsConstraintSet::computeConstantBound(
+        mlir::presburger::BoundType::UB, var, nullptr, true);
+    if (failed(lbBound) || failed(ubBound))
+      return std::nullopt;
+    if (type == presburger::BoundType::LB) {
+      if (tripCount.has_value())
+        tripCount =
+            std::min(*tripCount, static_cast<uint64_t>(lbBound.value()));
+      else
+        tripCount = lbBound.value();
+    } else if (type == presburger::BoundType::UB) {
+      if (tripCount.has_value())
+        tripCount =
+            std::min(*tripCount, static_cast<uint64_t>(ubBound.value()));
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linuxlonelyeagle wrote:

Thanks for pointing this out, I think using `std::max` is more appropriate here.

https://github.com/llvm/llvm-project/pull/128113