[flang] add hlfir.no_reassoc definition

[jeanPerier]

Summary

Same as fir.no_reassoc but accepts hlfir.expr type. It is needed because
FIR operation can only produce FIR types, and I do not want to change
that for now.

Depends on D139519

[clementval]

LGTM

[jeanPerier]

rebase

[vzakhari]

I wonder if we want to keep https://github.com/llvm/llvm-project/blob/main/flang/docs/HighLevelFIR.md in sync with HLFIROps.td. It may be okay to skip it, if it is a temporary solution.

flang/include/flang/Optimizer/HLFIR/HLFIROps.h

 //===-- HLFIROps.h - FIR operations -----------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef FORTRAN_OPTIMIZER_HLFIR_HLFIROPS_H
 #define FORTRAN_OPTIMIZER_HLFIR_HLFIROPS_H
 
 #include "flang/Optimizer/Dialect/FIRAttr.h"
 #include "flang/Optimizer/Dialect/FIRType.h"
 #include "flang/Optimizer/Dialect/FortranVariableInterface.h"
 #include "flang/Optimizer/HLFIR/HLFIRDialect.h"
+#include "mlir/Interfaces/InferTypeOpInterface.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
 
 #define GET_OP_CLASSES
 #include "flang/Optimizer/HLFIR/HLFIROps.h.inc"
 
 #endif // FORTRAN_OPTIMIZER_HLFIR_HLFIROPS_H

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

def hlfir_AsExprOp : hlfir_Op<"as_expr", []> {
   let assemblyFormat = [{
     $var attr-dict `:` functional-type(operands, results)
   }];
 
 
   let builders = [OpBuilder<(ins "mlir::Value":$var)>];
 }
 
+def hlfir_NoReassocOp : hlfir_Op<"no_reassoc", [NoMemoryEffect, SameOperandsAndResultType]> {
+  let summary = "synthetic op to prevent reassociation";
+
+  let description = [{
+    Same as fir.reassoc, except it accepts hlfir.expr arguments.
+  }];
+
+  let arguments = (ins AnyFortranEntity:$val);
+  let results = (outs AnyFortranEntity);
+
+  let assemblyFormat = "$val attr-dict `:` type($val)";
+}
+
 
 #endif // FORTRAN_DIALECT_HLFIR_OPS

flang/test/HLFIR/no_reassoc.fir

+// Test hlfir.no_reassoc operation parse, verify (no errors), and unparse.
+
+// RUN: fir-opt %s | fir-opt | FileCheck %s
+
+func.func @no_reassoc_value(%arg0: i32) {
+  %0 = hlfir.no_reassoc %arg0 : i32
+  return
+}
+// CHECK-LABEL: func.func @no_reassoc_value(
+// CHECK-SAME:    %[[VAL_0:.*]]: i32) {
+// CHECK:   hlfir.no_reassoc %[[VAL_0]] : i32
+
+func.func @no_reassoc_var(%arg0: !fir.ref<i32>) {
+  %0 = hlfir.no_reassoc %arg0 : !fir.ref<i32>
+  return
+}
+// CHECK-LABEL: func.func @no_reassoc_var(
+// CHECK-SAME:    %[[VAL_0:.*]]: !fir.ref<i32>) {
+// CHECK:   hlfir.no_reassoc %[[VAL_0]] : !fir.ref<i32>
+
+func.func @no_reassoc_expr(%arg0: !hlfir.expr<10xi32>) {
+  %0 = hlfir.no_reassoc %arg0 : !hlfir.expr<10xi32>
+  return
+}
+// CHECK-LABEL: func.func @no_reassoc_expr(
+// CHECK-SAME:    %[[VAL_0:.*]]: !hlfir.expr<10xi32>) {
+// CHECK:   hlfir.no_reassoc %[[VAL_0]] : !hlfir.expr<10xi32>