[Flang] Fix a crash when equivalence and namelist statements are used

[ceseo]

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

[llvmbot]

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

Author: Carlos Seo (ceseo)

Changes

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

---

Full diff: https://github.com/llvm/llvm-project/pull/150081.diff

2 Files Affected:

• (modified) flang/lib/Lower/IO.cpp (+3-1)
• (added) flang/test/Lower/equivalence-3.f (+19)

diff --git a/flang/lib/Lower/IO.cpp b/flang/lib/Lower/IO.cpp
index 53bf61922392d..087617ae86d3f 100644
--- a/flang/lib/Lower/IO.cpp
+++ b/flang/lib/Lower/IO.cpp
@@ -466,8 +466,10 @@ 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);
diff --git a/flang/test/Lower/equivalence-3.f b/flang/test/Lower/equivalence-3.f
new file mode 100644
index 0000000000000..19f8880189f0c
--- /dev/null
+++ b/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

[ceseo]

Forgot to put in the commit message, but this will fix #124489

[tblah]

LGTM, thanks. Please backport this to LLVM 21 if possible.