[flang] Handle character constant for error code in STOP stmt

[clementval]

Summary

Handle character constant ofr error code in the STOP statement.

Depends on D118992

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

[kiranchandramohan]

LGTM.

flang/lib/Lower/Runtime.cpp

void Fortran::lower::genStopStatement(
   // First operand is stop code (zero if absent)
   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");
+          callee = fir::runtime::getRuntimeFunc<mkRTKey(StopStatementText)>(
+              loc, builder);
+          calleeType = callee.getType();
+          // Creates a pair of operands for the CHARACTER and its LEN.
+          operands.push_back(
+              builder.createConvert(loc, calleeType.getInput(0), x.getAddr()));
+          operands.push_back(
+              builder.createConvert(loc, calleeType.getInput(1), x.getLen()));
         },
         [&](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);

flang/test/Lower/stop-statement.f90

 subroutine stop_quiet_constant()
   stop, quiet = .true.
  ! CHECK-DAG: %[[true:.*]] = arith.constant true
  ! CHECK-DAG: %[[false:.*]] = arith.constant false
  ! CHECK-DAG: %[[c0:.*]] = arith.constant 0 : i32
  ! CHECK: fir.call @_Fortran{{.*}}StopStatement(%[[c0]], %[[false]], %[[true]])
  ! CHECK-NEXT: fir.unreachable
 end subroutine
+
+! CHECK-LABEL stop_char_lit
+subroutine stop_char_lit
+  ! CHECK-DAG: %[[false:.*]] = arith.constant false
+  ! CHECK-DAG: %[[five:.*]] = arith.constant 5 : index
+  ! CHECK-DAG: %[[lit:.*]] = fir.address_of(@_QQ{{.*}}) : !fir.ref<!fir.char<1,5>>
+  ! CHECK-DAG: %[[buff:.*]] = fir.convert %[[lit]] : (!fir.ref<!fir.char<1,5>>) -> !fir.ref<i8>
+  ! CHECK-DAG: %[[len:.*]] = fir.convert %[[five]] : (index) -> i64
+  ! CHECK: fir.call @{{.*}}StopStatementText(%[[buff]], %[[len]], %[[false]], %[[false]]) :
+  ! CHECK-NEXT: fir.unreachable
+  stop 'crash'
+end subroutine stop_char_lit