[fir] Add fir.array_amend operation definition

[clementval]

Summary

This patch adds the fir.array_amend operation. this op
is used later in upstreaming patches for the F95 compliance.

The array_amend operation marks an array value as having been changed via
a reference obtain by an array_access. It acts as a logical transaction
log that is used to merge the final result back with an array_merge_store
operation.

mlir
  // fetch the value of one of the array value's elements
  %1 = fir.array_access %v, %i, %j : (!fir.array<?x?xT>, index, index) -> !fir.ref<T>
  // modify the element by storing data using %1 as a reference
  %2 = ... %1 ...
  // mark the array value
  %new_v = fir.array_amend %v, %2 : (!fir.array<?x?xT>, !fir.ref<T>) -> !fir.array<?x?xT>

This patch is part of the upstreaming effort from fir-dev branch.

Co-authored-by: Eric Schweitz <[e-mail]>

[clementval]

Update operation description + rebase

[kiranchandramohan]

LG.

flang/include/flang/Optimizer/Dialect/FIROps.td

1603

Nit: obtained

[clementval]

Rebase + typo

flang/include/flang/Optimizer/Dialect/FIROps.td

def fir_ArrayAccessOp : fir_Op<"array_access", [AttrSizedOperandSegments,
   let assemblyFormat = [{
     $sequence `,` $indices (`typeparams` $typeparams^)? attr-dict `:`
       functional-type(operands, results)
   }];
 
   let verifier = "return ::verify(*this);";
 }
 
+def fir_ArrayAmendOp : fir_Op<"array_amend", [NoSideEffect]> {
+  let summary = "Mark an array value as having been changed by reference.";
+
+  let description = [{
+    The `array_amend` operation marks an array value as having been changed via
+    a reference obtained by an `array_access`. It acts as a logical transaction
+    log that is used to merge the final result back with an `array_merge_store`
+    operation.
+
+    ```mlir
+      // fetch the value of one of the array value's elements
+      %1 = fir.array_access %v, %i, %j : (!fir.array<?x?xT>, index, index) -> !fir.ref<T>
+      // modify the element by storing data using %1 as a reference
+      %2 = ... %1 ...
+      // mark the array value
+      %new_v = fir.array_amend %v, %2 : (!fir.array<?x?xT>, !fir.ref<T>) -> !fir.array<?x?xT>
+    ```
+
+    More information about `array_amend` and other array operations can be
+    found in flang/docs/FIRArrayOperations.md.
+  }];
+
+  let arguments = (ins
+    fir_SequenceType:$sequence,
+    fir_ReferenceType:$memref
+  );
+
+  let results = (outs fir_SequenceType);
+
+  let assemblyFormat = [{
+    $sequence `,` $memref attr-dict `:` functional-type(operands, results)
+  }];
+}
+
 def fir_ArrayMergeStoreOp : fir_Op<"array_merge_store",
     [AttrSizedOperandSegments]> {
 
   let summary = "Store merged array value to memory.";
 
   let description = [{
     Store a merged array value to memory.
 

flang/test/Fir/fir-ops.fir

func @array_access_ops(%a : !fir.ref<!fir.array<?x?xf32>>) {
   %n = arith.constant 0 : index
   %m = arith.constant 50 : index
   %s = fir.shape %n, %m : (index, index) -> !fir.shape<2>
   %v = fir.array_load %a(%s) : (!fir.ref<!fir.array<?x?xf32>>, !fir.shape<2>) -> !fir.array<?x?xf32>
   %p = fir.array_access %v, %c1, %c1 : (!fir.array<?x?xf32>, index, index) -> !fir.ref<f32>
   // CHECK: %{{.*}} = fir.array_access %{{.*}}, %{{.*}}, %{{.*}} : (!fir.array<?x?xf32>, index, index) -> !fir.ref<f32>
   return
 }
+
+func @array_amend_ops(%a : !fir.ref<!fir.array<?x?xf32>>) {
+  %c1 = arith.constant 1 : index
+  %n = arith.constant 0 : index
+  %m = arith.constant 50 : index
+  %s = fir.shape %n, %m : (index, index) -> !fir.shape<2>
+  %v = fir.array_load %a(%s) : (!fir.ref<!fir.array<?x?xf32>>, !fir.shape<2>) -> !fir.array<?x?xf32>
+  %p = fir.array_access %v, %c1, %c1 : (!fir.array<?x?xf32>, index, index) -> !fir.ref<f32>
+  %res = fir.array_amend %v, %p : (!fir.array<?x?xf32>, !fir.ref<f32>) -> !fir.array<?x?xf32>
+  // CHECK: %{{.*}} = fir.array_amend %{{.*}}, %{{.*}} : (!fir.array<?x?xf32>, !fir.ref<f32>) -> !fir.array<?x?xf32>
+  return
+}