[flang] Add hlfir.as_expr definition

[jeanPerier]

Summary

hlfir.as_expr allows taking a value from a character, derived type,
or array expressions. This will allow implementing parentheses.

Combining as_expr + hlfir.associate will allow creating a variable copy
into a new temporary variable.

A later patch will add the ability to "move" a variable into an
expression (to give ownership of the variable storage to the expression,
with the commitment that the variable will not be used anymore).

[clementval]

LGTM. Looks like the patch cannot be applied correctly.

[jeanPerier]

rebase

[jeanPerier]

In D139519#3977676, @clementval wrote:

LGTM. Looks like the patch cannot be applied correctly.

Right, I rebased and it did not fix, it looks like there may be a bot issue given the message. I will wait this gets fix before merging:

Another git process seems to be running in this repository, e.g.
an editor opened by 'git commit'. Please make sure all processes
are terminated then try again. If it still fails, a git process
may have crashed in this repository earlier:
remove the file manually to continue.')
INFO    Syncing local, origin and upstream...
INFO    Backing off reset_repository(...) for 9.9s (git.exc.GitCommandError: Cmd('git') failed due to: exit code(128)
  cmdline: git reset --hard
  stderr: 'fatal: Unable to create '/var/lib/buildkite-agent/builds/llvm-project-fork/.git/index.lock': File exists.

[clementval]

In D139519#3977705, @jeanPerier wrote:

Right, I rebased and it did not fix, it looks like there may be a bot issue given the message. I will wait this gets fix before merging:

Another git process seems to be running in this repository, e.g.
an editor opened by 'git commit'. Please make sure all processes
are terminated then try again. If it still fails, a git process
may have crashed in this repository earlier:
remove the file manually to continue.')
INFO    Syncing local, origin and upstream...
INFO    Backing off reset_repository(...) for 9.9s (git.exc.GitCommandError: Cmd('git') failed due to: exit code(128)
  cmdline: git reset --hard
  stderr: 'fatal: Unable to create '/var/lib/buildkite-agent/builds/llvm-project-fork/.git/index.lock': File exists.

Yeah looks like pre-commit checks are quite slow since yesterday. It might be related. If you are confident with the patch just land it.

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

def hlfir_EndAssociateOp : hlfir_Op<"end_associate", []> {
 
   let assemblyFormat = [{
     $var `,` $must_free attr-dict `:` type(operands)
   }];
 
   let builders = [OpBuilder<(ins "hlfir::AssociateOp":$associate)>];
 }
 
+def hlfir_AsExprOp : hlfir_Op<"as_expr", []> {
+  let summary = "Take the value of an array, character or derived expression";
+
+  let description = [{
+    Take the value of an array, character or derived expression.
+  }];
+
+  let arguments = (ins AnyFortranVariable:$var);
+  let results = (outs hlfir_ExprType);
+
+  let assemblyFormat = [{
+    $var attr-dict `:` functional-type(operands, results)
+  }];
+
+
+  let builders = [OpBuilder<(ins "mlir::Value":$var)>];
+}
+
+
 #endif // FORTRAN_DIALECT_HLFIR_OPS

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

 
 void hlfir::EndAssociateOp::build(mlir::OpBuilder &builder,
                                   mlir::OperationState &result,
                                   hlfir::AssociateOp associate) {
   return build(builder, result, associate.getFirBase(),
                associate.getMustFreeStrorageFlag());
 }
 
+//===----------------------------------------------------------------------===//
+// AsExprOp
+//===----------------------------------------------------------------------===//
+
+void hlfir::AsExprOp::build(mlir::OpBuilder &builder,
+                            mlir::OperationState &result, mlir::Value var) {
+  hlfir::ExprType::Shape typeShape;
+  mlir::Type type = getFortranElementOrSequenceType(var.getType());
+  if (auto seqType = type.dyn_cast<fir::SequenceType>()) {
+    typeShape.append(seqType.getShape().begin(), seqType.getShape().end());
+    type = seqType.getEleTy();
+  }
+
+  auto resultType = hlfir::ExprType::get(builder.getContext(), typeShape, type,
+                                         /*isPolymorphic: TODO*/ false);
+  return build(builder, result, resultType, var);
+}
+
 #define GET_OP_CLASSES
 #include "flang/Optimizer/HLFIR/HLFIROps.cpp.inc"

flang/test/HLFIR/as_expr.fir

+// Test hlfir.as_expr operation parse, verify (no errors), and unparse.
+
+// RUN: fir-opt %s | fir-opt | FileCheck %s
+
+func.func @char_expr(%arg0: !fir.boxchar<1>) {
+  %0 = hlfir.as_expr %arg0 : (!fir.boxchar<1>) -> !hlfir.expr<!fir.char<1,?>>
+  return
+}
+// CHECK-LABEL: func.func @char_expr(
+// CHECK-SAME:    %[[VAL_0:.*]]: !fir.boxchar<1>) {
+// CHECK:   hlfir.as_expr %[[VAL_0]] : (!fir.boxchar<1>) -> !hlfir.expr<!fir.char<1,?>>
+
+func.func @char_expr_2(%arg0: !fir.ref<!fir.char<1,10>>) {
+  %0 = hlfir.as_expr %arg0 : (!fir.ref<!fir.char<1,10>>) -> !hlfir.expr<!fir.char<1,10>>
+  return
+}
+// CHECK-LABEL: func.func @char_expr_2(
+// CHECK-SAME:    %[[VAL_0:.*]]: !fir.ref<!fir.char<1,10>>) {
+// CHECK:   hlfir.as_expr %[[VAL_0]] : (!fir.ref<!fir.char<1,10>>) -> !hlfir.expr<!fir.char<1,10>>
+
+func.func @array_expr(%arg0: !fir.box<!fir.array<?xi32>>) {
+  %0 = hlfir.as_expr %arg0 : (!fir.box<!fir.array<?xi32>>) -> !hlfir.expr<?xi32>
+  return
+}
+// CHECK-LABEL: func.func @array_expr(
+// CHECK-SAME:    %[[VAL_0:.*]]: !fir.box<!fir.array<?xi32>>) {
+// CHECK:   hlfir.as_expr %[[VAL_0]] : (!fir.box<!fir.array<?xi32>>) -> !hlfir.expr<?xi32>
+
+func.func @array_expr_2(%arg0: !fir.ref<!fir.array<10xi32>>) {
+  %0 = hlfir.as_expr %arg0 : (!fir.ref<!fir.array<10xi32>>) -> !hlfir.expr<10xi32>
+  return
+}
+// CHECK-LABEL: func.func @array_expr_2(
+// CHECK-SAME:    %[[VAL_0:.*]]: !fir.ref<!fir.array<10xi32>>) {
+// CHECK:   hlfir.as_expr %[[VAL_0]] : (!fir.ref<!fir.array<10xi32>>) -> !hlfir.expr<10xi32>