[flang-commits] [flang] [flang] Region-based HLFIR operation for conditional expressions lowering (PR #194411)

[via flang-commits]

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@@ -857,6 +858,137 @@ struct CharExtremumOpConversion
   }
 };
 
+struct ConditionalOpConversion
+    : public mlir::OpConversionPattern<hlfir::ConditionalOp> {
+  using mlir::OpConversionPattern<hlfir::ConditionalOp>::OpConversionPattern;
+  explicit ConditionalOpConversion(mlir::MLIRContext *ctx)
+      : mlir::OpConversionPattern<hlfir::ConditionalOp>{ctx} {
+    // This pattern recursively converts nested ConditionalOp's
+    // by cloning and then converting them, so we have to allow
+    // for recursive pattern application. The recursion is bounded
+    // by the nesting level of ConditionalOp's.
+    setHasBoundedRewriteRecursion();
+  }
+  /// Compute the MLIR type of the temp's DeclareOp base result,
+  /// given the hlfir.expr type of the conditional. This must match
+  /// what createAndDeclareTemp + hlfir::DeclareOp would produce.
+  static mlir::Type computeTempBaseType(fir::FirOpBuilder &builder,
+                                        hlfir::ExprType exprType) {
+    const mlir::Type eleTy{exprType.getEleTy()};
+    const bool isPolymorphic{exprType.isPolymorphic()};
+    const bool isArray{exprType.isArray()};
+    mlir::Type elemOrSeqType{eleTy};
+    if (isArray)
+      elemOrSeqType = fir::SequenceType::get(exprType.getShape(), eleTy);
+    // Polymorphic: runtime allocate produces fir.class<fir.heap<T>>,
+    // DeclareOp strips the heap attribute → fir.class<T>.
+    if (isPolymorphic)
+      return fir::ClassType::get(elemOrSeqType);
+    // Arrays (non-polymorphic): heap alloc → fir.heap<seqTy>,
+    // DeclareOp wraps in box → fir.box<seqTy>.
+    if (isArray)
+      return fir::BoxType::get(elemOrSeqType);
+    // Scalar, non-polymorphic.
+    if (auto charTy{mlir::dyn_cast<fir::CharacterType>(eleTy)})
+      if (charTy.hasDynamicLen())
+        return fir::BoxCharType::get(builder.getContext(), charTy.getFKind());
+    if (fir::isRecordWithTypeParameters(eleTy))
+      return fir::BoxType::get(eleTy);
+    return fir::ReferenceType::get(eleTy);
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jeanPerier wrote:

There is no helper currently, but I think one should be added to get the canonical variable type for an hlfir::ExprType.

See existing similar logic [here](https://github.com/llvm/llvm-project/blob/da855875ff6b023e4a77d9cdb9e6709a2e66c3fc/flang/lib/Optimizer/HLFIR/IR/HLFIROps.cpp#L1753-L1761).

You can probably move the hlfir::DeclareOp::getHLFIRVariableType to some HLFIRDialect.h helper add one that take an `hlfir::ExprType` entry (without lower bound arguments) (next to `genExprType` [here](https://github.com/llvm/llvm-project/blob/3efe6d48739e384462b92af3f70dbb6a8141e010/flang/include/flang/Optimizer/HLFIR/HLFIRDialect.h#L66) for instance that does the opposit).

https://github.com/llvm/llvm-project/pull/194411