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

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.

Reviewed By: kiranchandramohan, schweitz

Differential Revision: https://reviews.llvm.org/D118993

flang/lib/Lower/Runtime.cpp

@@ -49,7 +49,14 @@ void Fortran::lower::genStopStatement(
                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)>(

flang/test/Lower/stop-statement.f90

@@ -51,3 +51,15 @@ subroutine stop_quiet()
  ! CHECK: fir.call @_Fortran{{.*}}StopStatement(%[[c0]], %[[false]], %[[bi1]])
  ! 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