[flang] Generalized simplification of HLFIR reduction ops. (llvm#136071)

This change generalizes SumAsElemental inlining in
SimplifyHLFIRIntrinsics pass so that it can be applied
to ALL, ANY, COUNT, MAXLOC, MAXVAL, MINLOC, MINVAL, SUM.

This change makes the special handling of the reduction
operations in OptimizedBufferization redundant: once HLFIR
operations are inlined, the hlfir.elemental inlining should
do the rest of the job.

Author: vzakhari

flang/include/flang/Optimizer/Builder/HLFIRTools.h

@@ -301,6 +301,11 @@ mlir::Value genExtent(mlir::Location loc, fir::FirOpBuilder &builder,
 mlir::Value genLBound(mlir::Location loc, fir::FirOpBuilder &builder,
                       hlfir::Entity entity, unsigned dim);
 
+/// Compute the lower bounds of \p entity, which is an array of known rank.
+llvm::SmallVector<mlir::Value> genLBounds(mlir::Location loc,
+                                          fir::FirOpBuilder &builder,
+                                          hlfir::Entity entity);
+
 /// Generate a vector of extents with index type from a fir.shape
 /// of fir.shape_shift value.
 llvm::SmallVector<mlir::Value> getIndexExtents(mlir::Location loc,

flang/lib/Optimizer/Builder/HLFIRTools.cpp

@@ -659,6 +659,33 @@ mlir::Value hlfir::genLBound(mlir::Location loc, fir::FirOpBuilder &builder,
   return dimInfo.getLowerBound();
 }
 
+llvm::SmallVector<mlir::Value> hlfir::genLBounds(mlir::Location loc,
+                                                 fir::FirOpBuilder &builder,
+                                                 hlfir::Entity entity) {
+  assert(!entity.isAssumedRank() &&
+         "cannot compute all lower bounds for assumed rank");
+  assert(!entity.isScalar() && "expected an array entity");
+  int rank = entity.getRank();
+  mlir::Type idxTy = builder.getIndexType();
+  if (!entity.mayHaveNonDefaultLowerBounds())
+    return {static_cast<std::size_t>(rank),
+            builder.createIntegerConstant(loc, idxTy, 1)};
+
+  if (auto shape = tryRetrievingShapeOrShift(entity)) {
+    auto lbounds = getExplicitLboundsFromShape(shape);
+    if (!lbounds.empty())
+      return lbounds;
+  }
+
+  if (entity.isMutableBox())
+    entity = hlfir::derefPointersAndAllocatables(loc, builder, entity);
+
+  llvm::SmallVector<mlir::Value, Fortran::common::maxRank> lbounds;
+  fir::factory::genDimInfoFromBox(builder, loc, entity, &lbounds,
+                                  /*extents=*/nullptr, /*strides=*/nullptr);
+  return lbounds;
+}
+
 void hlfir::genLengthParameters(mlir::Location loc, fir::FirOpBuilder &builder,
                                 Entity entity,
                                 llvm::SmallVectorImpl<mlir::Value> &result) {