Change result char type length to unknown

The runtime Trim function allocates the result, that may have a
different length than its input character string.

Author: luporl

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

@@ -860,15 +860,11 @@ void hlfir::CmpCharOp::getEffects(
 
 void hlfir::CharTrimOp::build(mlir::OpBuilder &builder,
                               mlir::OperationState &result, mlir::Value chr) {
-  fir::CharacterType::LenType len;
-  if (auto cstLen = getCharacterLengthIfStatic(chr.getType()))
-    len = *cstLen;
-  else
-    len = fir::CharacterType::unknownLen();
   unsigned kind = getCharacterKind(chr.getType());
   auto resultType = hlfir::ExprType::get(
       builder.getContext(), hlfir::ExprType::Shape{},
-      fir::CharacterType::get(builder.getContext(), kind, len),
+      fir::CharacterType::get(builder.getContext(), kind,
+                              fir::CharacterType::unknownLen()),
       /*polymorphic=*/false);
   build(builder, result, resultType, chr);
 }

flang/test/Lower/HLFIR/trim.f90

@@ -20,3 +20,13 @@ subroutine trim_test(c)
   tc = trim(c)
 end subroutine
 
+! Test trim with fixed length character.
+! The length of the returned character type must be unknown.
+! CHECK-LABEL:  func.func @_QPtrim_test2(
+! CHECK:          hlfir.char_trim %{{.*}}#0 : (!fir.ref<!fir.char<1,8>>) -> !hlfir.expr<!fir.char<1,?>>
+subroutine trim_test2(c)
+  character(8) :: c
+  character(8) :: tc
+
+  tc = trim(c)
+end subroutine

flang/test/Lower/volatile-string.f90

@@ -68,9 +68,9 @@ subroutine assign_different_length(string)
 ! CHECK:           %[[VAL_37:.*]] = hlfir.as_expr %[[VAL_36]]#0 move %[[VAL_0]] : (!fir.heap<!fir.char<1,3>>, i1) -> !hlfir.expr<!fir.char<1,3>>
 ! CHECK:           hlfir.assign %[[VAL_37]] to %[[VAL_14]]#0 : !hlfir.expr<!fir.char<1,3>>, !fir.ref<!fir.char<1,3>, volatile>
 ! CHECK:           hlfir.destroy %[[VAL_37]] : !hlfir.expr<!fir.char<1,3>>
-! CHECK:           %[[VAL_38:.*]] = hlfir.char_trim %[[VAL_14]]#0 : (!fir.ref<!fir.char<1,3>, volatile>) -> !hlfir.expr<!fir.char<1,3>>
-! CHECK:           hlfir.assign %[[VAL_38]] to %[[VAL_11]]#0 : !hlfir.expr<!fir.char<1,3>>, !fir.ref<!fir.char<1,3>>
-! CHECK:           hlfir.destroy %[[VAL_38]] : !hlfir.expr<!fir.char<1,3>>
+! CHECK:           %[[VAL_38:.*]] = hlfir.char_trim %[[VAL_14]]#0 : (!fir.ref<!fir.char<1,3>, volatile>) -> !hlfir.expr<!fir.char<1,?>>
+! CHECK:           hlfir.assign %[[VAL_38]] to %[[VAL_11]]#0 : !hlfir.expr<!fir.char<1,?>>, !fir.ref<!fir.char<1,3>>
+! CHECK:           hlfir.destroy %[[VAL_38]] : !hlfir.expr<!fir.char<1,?>>
 ! CHECK:           hlfir.assign %[[VAL_14]]#0 to %[[VAL_11]]#0 : !fir.ref<!fir.char<1,3>, volatile>, !fir.ref<!fir.char<1,3>>
 ! CHECK:           return
 ! CHECK:         }