[flang] Simple folding for hlfir.shape_of. (#119649)

This folding makes sure there are no hlfir.shape_of users
of hlfir.elemental - this may enable more InlineElementals matches,
because it is looking for exactly two uses of an hlfir.elemental.

flang/include/flang/Optimizer/HLFIR/HLFIROps.td

@@ -1205,6 +1205,7 @@ def hlfir_ShapeOfOp : hlfir_Op<"shape_of", [Pure]> {
   }];
 
   let builders = [OpBuilder<(ins "mlir::Value":$expr)>];
+  let hasFolder = 1;
 }
 
 def hlfir_GetExtentOp : hlfir_Op<"get_extent", [Pure]> {

flang/lib/Optimizer/HLFIR/IR/HLFIROps.cpp

@@ -1704,6 +1704,15 @@ hlfir::ShapeOfOp::canonicalize(ShapeOfOp shapeOf,
   return llvm::LogicalResult::success();
 }
 
+mlir::OpFoldResult hlfir::ShapeOfOp::fold(FoldAdaptor adaptor) {
+  if (matchPattern(getExpr(), mlir::m_Op<hlfir::ElementalOp>())) {
+    auto elementalOp =
+        mlir::cast<hlfir::ElementalOp>(getExpr().getDefiningOp());
+    return elementalOp.getShape();
+  }
+  return {};
+}
+
 //===----------------------------------------------------------------------===//
 // GetExtent
 //===----------------------------------------------------------------------===//

flang/test/HLFIR/shapeof.fir

@@ -27,3 +27,21 @@ func.func @shapeof2(%arg0: !hlfir.expr<?x2xi32>) -> !fir.shape<2> {
 // CHECK-ALL:          %[[EXPR:.*]]: !hlfir.expr<?x2xi32>
 // CHECK-ALL-NEXT:   %[[SHAPE:.*]] = hlfir.shape_of %[[EXPR]] : (!hlfir.expr<?x2xi32>) -> !fir.shape<2>
 // CHECK-ALL-NEXT:   return %[[SHAPE]]
+
+// Checks hlfir.elemental -> hlfir.shape_of folding
+func.func @shapeof_fold1(%extent: index) -> !fir.shape<1> {
+  %shape1 = fir.shape %extent : (index) -> !fir.shape<1>
+  %elem = hlfir.elemental %shape1 : (!fir.shape<1>) -> !hlfir.expr<?xindex> {
+    hlfir.yield_element %extent : index
+  }
+  %shape2 = hlfir.shape_of %elem : (!hlfir.expr<?xindex>) -> !fir.shape<1>
+  return %shape2 : !fir.shape<1>
+}
+// CHECK-ALL-LABEL:   func.func @shapeof_fold1(
+// CHECK-ALL-SAME:        %[[VAL_0:.*]]: index) -> !fir.shape<1> {
+// CHECK-CANON-NEXT:    %[[VAL_1:.*]] = fir.shape %[[VAL_0]] : (index) -> !fir.shape<1>
+// CHECK-CANON-NEXT:    %[[VAL_2:.*]] = hlfir.elemental %[[VAL_1]] : (!fir.shape<1>) -> !hlfir.expr<?xindex> {
+// CHECK-CANON-NEXT:      hlfir.yield_element %[[VAL_0]] : index
+// CHECK-CANON-NEXT:    }
+// CHECK-CANON-NEXT:    return %[[VAL_1]] : !fir.shape<1>
+// CHECK-CANON-NEXT:  }