[Flang] Fix a crash when equivalence and namelist statements are used (#150081)

Check for equivalence when generating namelist descriptors in IO.cpp.

Fixes #124489

Author: ceseo

flang/lib/Lower/IO.cpp

@@ -464,8 +464,10 @@ getNamelistGroup(Fortran::lower::AbstractConverter &converter,
       fir::BoxType boxTy =
           fir::BoxType::get(fir::PointerType::get(converter.genType(s)));
       auto descFunc = [&](fir::FirOpBuilder &b) {
+        bool couldBeInEquivalence =
+            Fortran::semantics::FindEquivalenceSet(s) != nullptr;
         auto box = Fortran::lower::genInitialDataTarget(
-            converter, loc, boxTy, *expr, /*couldBeInEquivalence=*/true);
+            converter, loc, boxTy, *expr, couldBeInEquivalence);
         b.create<fir::HasValueOp>(loc, box);
       };
       builder.createGlobalConstant(loc, boxTy, mangleName, descFunc, linkOnce);

flang/test/Lower/equivalence-3.f

@@ -0,0 +1,19 @@
+! RUN: bbc -emit-fir -o - %s | FileCheck %s
+
+  ! CHECK-LABEL: func @_QQmain
+  program main
+  real a1,a2
+  equivalence (a1,a2)
+  ! A fir.alloca should never appear in a global constant initialization.
+  ! CHECK: fir.global linkonce @_QFEx1.desc constant : !fir.box<!fir.ptr<!fir.array<5xf64>>>
+  ! CHECK: arith.constant 5 : index
+  ! CHECK:fir.address_of(@_QFEx1) : !fir.ref<!fir.array<5xf64>>
+  ! CHECK: fir.shape %c5 : (index) -> !fir.shape<1>
+  ! CHECK: fir.declare %0(%1) {uniq_name = "_QFEx1"} : (!fir.ref<!fir.array<5xf64>>, !fir.shape<1>) -> !fir.ref<!fir.array<5xf64>>
+  ! CHECK: fir.embox %2(%1) : (!fir.ref<!fir.array<5xf64>>, !fir.shape<1>) -> !fir.box<!fir.array<5xf64>>
+  ! CHECK: fir.rebox %3 : (!fir.box<!fir.array<5xf64>>) -> !fir.box<!fir.ptr<!fir.array<5xf64>>>
+  ! CHECK: fir.has_value %4 : !fir.box<!fir.ptr<!fir.array<5xf64>>>
+  real*8 x1(5)
+  namelist /y1/x1
+  read (5,y1)
+  end