[flang] Re-land PR#97337

[klausler]

Pull request #97337 was
reverted by #98612 due
to two failing tests in llvm-test-suite -- which I ran, as always,
but must have bungled or misinterpreted (mea culpa).

The failing tests were llvm-test-suite/Fortran/gfortran/regression/
char_length_{20,21}.f90. They have array constructors with
explicit character types whose dynamic length values are negative
at runtime, which must be interpreted as zero.

This patch extends the original to cover those cases.

[llvmbot]

@llvm/pr-subscribers-flang-fir-hlfir

@llvm/pr-subscribers-flang-semantics

Author: Peter Klausler (klausler)

Changes

Pull request #97337 was
reverted by #98612 due
to two failing tests in llvm-test-suite -- which I ran, as always,
but must have bungled or misinterpreted (mea culpa).

The failing tests were llvm-test-suite/Fortran/gfortran/regression/
char_length_{20,21}.f90. They have array constructors with
explicit character types whose dynamic length values are negative
at runtime, which must be interpreted as zero.

This patch extends the original to cover those cases.

---

Full diff: https://github.com/llvm/llvm-project/pull/98656.diff

3 Files Affected:

• (modified) flang/lib/Semantics/expression.cpp (+12-4)
• (modified) flang/test/Lower/HLFIR/array-ctor-character.f90 (+5-4)
• (modified) flang/test/Semantics/array-constr-len.f90 (-1)

diff --git a/flang/lib/Semantics/expression.cpp b/flang/lib/Semantics/expression.cpp
index 90900d9acb6ad..2d91962a24a4c 100644
--- a/flang/lib/Semantics/expression.cpp
+++ b/flang/lib/Semantics/expression.cpp
@@ -63,7 +63,7 @@ std::optional<Expr<SubscriptInteger>> DynamicTypeWithLength::LEN() const {
 }
 
 static std::optional<DynamicTypeWithLength> AnalyzeTypeSpec(
-    const std::optional<parser::TypeSpec> &spec) {
+    const std::optional<parser::TypeSpec> &spec, FoldingContext &context) {
   if (spec) {
     if (const semantics::DeclTypeSpec *typeSpec{spec->declTypeSpec}) {
       // Name resolution sets TypeSpec::declTypeSpec only when it's valid
@@ -80,7 +80,13 @@ static std::optional<DynamicTypeWithLength> AnalyzeTypeSpec(
             const semantics::ParamValue &len{cts.length()};
             // N.B. CHARACTER(LEN=*) is allowed in type-specs in ALLOCATE() &
             // type guards, but not in array constructors.
-            return DynamicTypeWithLength{DynamicType{kind, len}};
+            DynamicTypeWithLength type{DynamicType{kind, len}};
+            if (auto lenExpr{type.LEN()}) {
+              type.length = Fold(context,
+                  AsExpr(Extremum<SubscriptInteger>{Ordering::Greater,
+                      Expr<SubscriptInteger>{0}, std::move(*lenExpr)}));
+            }
+            return type;
           } else {
             return DynamicTypeWithLength{DynamicType{category, kind}};
           }
@@ -1584,7 +1590,8 @@ class ArrayConstructorContext {
   std::optional<Expr<SubscriptInteger>> LengthIfGood() const {
     if (type_) {
       auto len{type_->LEN()};
-      if (len && IsConstantExpr(*len) && !ContainsAnyImpliedDoIndex(*len)) {
+      if (explicitType_ ||
+          (len && IsConstantExpr(*len) && !ContainsAnyImpliedDoIndex(*len))) {
         return len;
       }
     }
@@ -1939,7 +1946,8 @@ MaybeExpr ArrayConstructorContext::ToExpr() {
 
 MaybeExpr ExpressionAnalyzer::Analyze(const parser::ArrayConstructor &array) {
   const parser::AcSpec &acSpec{array.v};
-  ArrayConstructorContext acContext{*this, AnalyzeTypeSpec(acSpec.type)};
+  ArrayConstructorContext acContext{
+      *this, AnalyzeTypeSpec(acSpec.type, GetFoldingContext())};
   for (const parser::AcValue &value : acSpec.values) {
     acContext.Add(value);
   }
diff --git a/flang/test/Lower/HLFIR/array-ctor-character.f90 b/flang/test/Lower/HLFIR/array-ctor-character.f90
index 85e6ed27fe077..881085b370ffe 100644
--- a/flang/test/Lower/HLFIR/array-ctor-character.f90
+++ b/flang/test/Lower/HLFIR/array-ctor-character.f90
@@ -93,10 +93,11 @@ subroutine test_set_length_sanitize(i, c1)
   call takes_char([character(len=i):: c1])
 end subroutine
 ! CHECK-LABEL:   func.func @_QPtest_set_length_sanitize(
-! CHECK:   %[[VAL_6:.*]]:2 = hlfir.declare {{.*}}Ec1
-! CHECK:   %[[VAL_9:.*]]:2 = hlfir.declare {{.*}}Ei
-! CHECK:   %[[VAL_25:.*]] = fir.load %[[VAL_9]]#0 : !fir.ref<i64>
+! CHECK:   %[[VAL_2:.*]]:2 = hlfir.declare {{.*}}Ec1
+! CHECK:   %[[VAL_3:.*]]:2 = hlfir.declare %arg0
+! CHECK:   %[[VAL_4:.*]] = fir.load %[[VAL_3]]#0 : !fir.ref<i64>
+! CHECK:   %[[VAL_25:.*]] = fir.load %[[VAL_3]]#0 : !fir.ref<i64>
 ! CHECK:   %[[VAL_26:.*]] = arith.constant 0 : i64
 ! CHECK:   %[[VAL_27:.*]] = arith.cmpi sgt, %[[VAL_25]], %[[VAL_26]] : i64
 ! CHECK:   %[[VAL_28:.*]] = arith.select %[[VAL_27]], %[[VAL_25]], %[[VAL_26]] : i64
-! CHECK:   %[[VAL_29:.*]] = hlfir.set_length %[[VAL_6]]#0 len %[[VAL_28]] : (!fir.boxchar<1>, i64) -> !hlfir.expr<!fir.char<1,?>>
+! CHECK:   %[[VAL_29:.*]] = hlfir.set_length %[[VAL_2]]#0 len %[[VAL_28]] : (!fir.boxchar<1>, i64) -> !hlfir.expr<!fir.char<1,?>>
diff --git a/flang/test/Semantics/array-constr-len.f90 b/flang/test/Semantics/array-constr-len.f90
index a785c9e2ece6d..4de9c76c7041c 100644
--- a/flang/test/Semantics/array-constr-len.f90
+++ b/flang/test/Semantics/array-constr-len.f90
@@ -10,6 +10,5 @@ subroutine subr(s,n)
   print *, [(s(1:j),j=1,0)]
   print *, [(s(1:1),j=1,0)] ! ok
   print *, [character(2)::(s(1:n),j=1,0)] ! ok
-  !ERROR: Array constructor implied DO loop has no iterations and indeterminate character length
   print *, [character(n)::(s(1:n),j=1,0)]
 end

[clementval]

LGTM