[flang] Lower integer constant code for STOP stmt

[clementval]

Summary

This patch lower the integer constant code in the STOP statement.

The code is lowered to arith.constant.

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

[kiranchandramohan]

LGTM.

flang/test/Lower/stop-statement.f90

27

Assuming the convert is removed by the canonicalize pass and that we don't have enough support for other types for the convert to be retained.

[clementval]

flang/test/Lower/stop-statement.f90

27

Not sure I follow your comment here. The output of ./bin/bbc -emit-fir (without --canonicalize ) is the following:

func @_QPss() {
  %c42_i32 = arith.constant 42 : i32
  %false = arith.constant false
  %false_0 = arith.constant false
  %0 = fir.call @_FortranAStopStatement(%c42_i32, %false, %false_0) : (i32, i1, i1) -> none
  fir.unreachable
^bb1:  // no predecessors
  return
}

So there is no convert.. Do you have smth else?

[kiranchandramohan]

flang/test/Lower/stop-statement.f90

27

Sorry, I completely missed the point that createConvert function checks whether the source and dest types are different and then only inserts the convert.

A test with a convert would be great. But if there is not enough infra that is OK.

[kiranchandramohan]

flang/test/Lower/stop-statement.f90

27

I just saw from the standard that the Stop code value has to be an integer of the default kind. So you can skip my comment.

[clementval]

Rebase

flang/lib/Lower/Runtime.cpp

void Fortran::lower::genStopStatement(
     Fortran::lower::AbstractConverter &converter,
     const Fortran::parser::StopStmt &stmt) {
   fir::FirOpBuilder &builder = converter.getFirOpBuilder();
   mlir::Location loc = converter.getCurrentLocation();
   llvm::SmallVector<mlir::Value> operands;
   mlir::FuncOp callee;
   mlir::FunctionType calleeType;
   // First operand is stop code (zero if absent)
-  if (std::get<std::optional<Fortran::parser::StopCode>>(stmt.t)) {
-    TODO(loc, "STOP first operand not lowered yet");
+  if (const auto &code =
+          std::get<std::optional<Fortran::parser::StopCode>>(stmt.t)) {
+    auto expr = converter.genExprValue(*Fortran::semantics::GetExpr(*code));
+    LLVM_DEBUG(llvm::dbgs() << "stop expression: "; expr.dump();
+               llvm::dbgs() << '\n');
+    expr.match(
+        [&](const fir::CharBoxValue &x) {
+          TODO(loc, "STOP CharBoxValue first operand not lowered yet");
+        },
+        [&](fir::UnboxedValue x) {
+          callee = fir::runtime::getRuntimeFunc<mkRTKey(StopStatement)>(
+              loc, builder);
+          calleeType = callee.getType();
+          mlir::Value cast =
+              builder.createConvert(loc, calleeType.getInput(0), x);
+          operands.push_back(cast);
+        },
+        [&](auto) {
+          mlir::emitError(loc, "unhandled expression in STOP");
+          std::exit(1);
+        });
   } else {
     callee = fir::runtime::getRuntimeFunc<mkRTKey(StopStatement)>(loc, builder);
     calleeType = callee.getType();
     operands.push_back(
         builder.createIntegerConstant(loc, calleeType.getInput(0), 0));
   }
 
   // Second operand indicates ERROR STOP

flang/test/Lower/stop-statement.f90

 subroutine stop_error()
  error stop
  ! CHECK-DAG: %[[c0:.*]] = arith.constant 0 : i32
  ! CHECK-DAG: %[[true:.*]] = arith.constant true
  ! CHECK-DAG: %[[false:.*]] = arith.constant false
  ! CHECK: fir.call @_Fortran{{.*}}StopStatement(%[[c0]], %[[true]], %[[false]])
  ! CHECK-NEXT: fir.unreachable
 end subroutine
+
+! CHECK-LABEL stop_code
+subroutine stop_code()
+  stop 42
+ ! CHECK-DAG: %[[c42:.*]] = arith.constant 42 : i32
+ ! CHECK-DAG: %[[false:.*]] = arith.constant false
+ ! CHECK: fir.call @_Fortran{{.*}}StopStatement(%[[c42]], %[[false]], %[[false]])
+ ! CHECK-NEXT: fir.unreachable
+end subroutine