[clang] dc245a0 - [CIR] Fixup 'zero' branch of Null Initialization (#225490)

[via cfe-commits]

Author: Erich Keane
Date: 2026-09-22T13:48:13-07:00
New Revision: dc245a0c5efb1fdc5344c1c8964323ae5219cf9c

URL: https://github.com/llvm/llvm-project/commit/dc245a0c5efb1fdc5344c1c8964323ae5219cf9c
DIFF: https://github.com/llvm/llvm-project/commit/dc245a0c5efb1fdc5344c1c8964323ae5219cf9c.diff

LOG: [CIR] Fixup 'zero' branch of Null Initialization (#225490)

The zero branch has a test for an NYI based on whether the thing is a
VLA or not. However, classic codegen uses 'dyn_cast_or_null', and we
used 'isa', so a nullptr caused an assert. This patch fixes it.

Added: 
    

Modified: 
    clang/lib/CIR/CodeGen/CIRGenFunction.cpp
    clang/test/CIR/CodeGen/class.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/CIR/CodeGen/CIRGenFunction.cpp b/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
index 64572144b5d83..d10c1802be539 100644
--- a/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
@@ -1383,7 +1383,7 @@ void CIRGenFunction::emitNullInitialization(mlir::Location loc, Address destPtr,
   const CharUnits size = getContext().getTypeSizeInChars(ty);
   if (size.isZero()) {
     // But note that getTypeInfo returns 0 for a VLA.
-    if (isa<VariableArrayType>(getContext().getAsArrayType(ty))) {
+    if (isa_and_nonnull<VariableArrayType>(getContext().getAsArrayType(ty))) {
       cgm.errorNYI(loc,
                    "emitNullInitialization for zero size VariableArrayType");
     } else {

diff  --git a/clang/test/CIR/CodeGen/class.cpp b/clang/test/CIR/CodeGen/class.cpp
index b04899feb29ff..afa5aab3f2d76 100644
--- a/clang/test/CIR/CodeGen/class.cpp
+++ b/clang/test/CIR/CodeGen/class.cpp
@@ -136,3 +136,67 @@ void usesTemplate() { takesTemplate(&Template<char>::m); }
 
 // OGCG: define dso_local void @_Z12usesTemplatev
 // OGCG: call void @_Z13takesTemplateM8TemplateIcEi(
+
+struct JustFam {
+  int m[0];
+};
+
+void fam_1() {
+  JustFam a;
+  (void)a.m;
+}
+// CIR: cir.func{{.*}}@_Z5fam_1v
+// CIR: %[[A:.*]] = cir.alloca "a" align(4) : !cir.ptr<!rec_JustFam>
+// CIR: cir.get_member %[[A]][0] {name = "m"} : !cir.ptr<!rec_JustFam> -> !cir.ptr<!cir.array<!s32i x 0>>
+
+// LLVM: define{{.*}}@_Z5fam_1v
+// LLVM: %[[A:.*]] = alloca %struct.JustFam, align 4
+// LLVM: getelementptr inbounds nuw %struct.JustFam, ptr %[[A]], i32 0, i32 0
+
+// OGCG: define{{.*}}@_Z5fam_1v
+// OGCG: %[[A:.*]] = alloca %struct.JustFam, align 4
+// OGCG: getelementptr inbounds nuw %struct.JustFam, ptr %[[A]], i32 0, i32 0
+
+void fam_2() {
+  JustFam a = JustFam();
+  (void)a.m;
+}
+
+// CIR: cir.func{{.*}}@_Z5fam_2v
+// CIR: %[[A:.*]] = cir.alloca "a" align(4) init : !cir.ptr<!rec_JustFam>
+// CIR: cir.get_member %[[A]][0] {name = "m"} : !cir.ptr<!rec_JustFam> -> !cir.ptr<!cir.array<!s32i x 0>>
+
+// LLVM: define{{.*}}@_Z5fam_2v
+// LLVM: %[[A:.*]] = alloca %struct.JustFam, align 4
+// LLVM: getelementptr inbounds nuw %struct.JustFam, ptr %[[A]], i32 0, i32 0
+
+// OGCG: define{{.*}}@_Z5fam_2v
+// OGCG: %[[A:.*]] = alloca %struct.JustFam, align 4
+// OGCG: getelementptr inbounds nuw %struct.JustFam, ptr %[[A]], i32 0, i32 0
+
+void fam_3() {
+  JustFam *a = new JustFam();
+  (void)a->m;
+}
+// CIR: cir.func{{.*}}@_Z5fam_3v
+// CIR: %[[A:.*]] = cir.alloca "a" align(8) init : !cir.ptr<!cir.ptr<!rec_JustFam>>
+// CIR: %[[ZERO:.*]] = cir.const #cir.int<0> : !u64i
+// CIR: %[[NEW:.*]] = cir.call @_Znwm(%[[ZERO]]) {allocsize = array<i32: 0>, builtin}
+// CIR: %[[NEW_TO_A:.*]] = cir.cast bitcast %[[NEW]] : !cir.ptr<!void> -> !cir.ptr<!rec_JustFam>
+// CIR: cir.store align(8) %[[NEW_TO_A]], %[[A]] : !cir.ptr<!rec_JustFam>, !cir.ptr<!cir.ptr<!rec_JustFam>>
+// CIR: %[[LOAD_A:.*]] = cir.load align(8) %[[A]] : !cir.ptr<!cir.ptr<!rec_JustFam>>, !cir.ptr<!rec_JustFam>
+// CIR: cir.get_member %[[LOAD_A]][0] {name = "m"} : !cir.ptr<!rec_JustFam> -> !cir.ptr<!cir.array<!s32i x 0>>
+
+// LLVM: define{{.*}}@_Z5fam_3v
+// LLVM: %[[A:.*]] = alloca ptr, align 8
+// LLVM: %[[NEW:.*]] = call noundef nonnull ptr @_Znwm(i64 noundef 0)
+// LLVM: store ptr %[[NEW]], ptr %[[A]], align 8
+// LLVM: %[[LOAD_A:.*]] = load ptr, ptr %[[A]], align 8
+// LLVM: getelementptr inbounds nuw %struct.JustFam, ptr %[[LOAD_A]], i32 0, i32 0
+
+// OGCG: define{{.*}}@_Z5fam_3v
+// OGCG: %[[A:.*]] = alloca ptr, align 8
+// OGCG: %[[NEW:.*]] = call noalias noundef nonnull ptr @_Znwm(i64 noundef 0)
+// OGCG: store ptr %[[NEW]], ptr %[[A]], align 8
+// OGCG: %[[LOAD_A:.*]] = load ptr, ptr %[[A]], align 8
+// OGCG: getelementptr inbounds nuw %struct.JustFam, ptr %[[LOAD_A]], i32 0, i32 0