[clang] [CIR] Implement emitAtomicInit for AggregateExpr (PR #161826)

[Amr Hesham via cfe-commits]

https://github.com/AmrDeveloper updated https://github.com/llvm/llvm-project/pull/161826

>From da997af2d3c455215ae713fa1a9fc5fce26defc3 Mon Sep 17 00:00:00 2001
From: Amr Hesham <amr96 at programmer.net>
Date: Fri, 3 Oct 2025 13:09:56 +0200
Subject: [PATCH] [CIR] Implement emitAtomicInit for AggregateExpr

---
 clang/lib/CIR/CodeGen/CIRGenAtomic.cpp | 20 ++++++++++++++++--
 clang/test/CIR/CodeGen/struct.cpp      | 28 ++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/clang/lib/CIR/CodeGen/CIRGenAtomic.cpp b/clang/lib/CIR/CodeGen/CIRGenAtomic.cpp
index e943b0252bf4e..0f4d6d20afc52 100644
--- a/clang/lib/CIR/CodeGen/CIRGenAtomic.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenAtomic.cpp
@@ -718,10 +718,26 @@ void CIRGenFunction::emitAtomicInit(Expr *init, LValue dest) {
     return;
   }
 
-  case cir::TEK_Aggregate:
-    cgm.errorNYI(init->getSourceRange(), "emitAtomicInit: aggregate type");
+  case cir::TEK_Aggregate: {
+    // Fix up the destination if the initializer isn't an expression
+    // of atomic type.
+    bool zeroed = false;
+    if (!init->getType()->isAtomicType()) {
+      zeroed = atomics.emitMemSetZeroIfNecessary();
+      dest = atomics.projectValue();
+    }
+
+    // Evaluate the expression directly into the destination.
+    assert(!cir::MissingFeatures::aggValueSlotGC());
+    AggValueSlot slot = AggValueSlot::forLValue(
+        dest, AggValueSlot::IsNotDestructed, AggValueSlot::IsNotAliased,
+        AggValueSlot::DoesNotOverlap,
+        zeroed ? AggValueSlot::IsZeroed : AggValueSlot::IsNotZeroed);
+
+    emitAggExpr(init, slot);
     return;
   }
+  }
 
   llvm_unreachable("bad evaluation kind");
 }
diff --git a/clang/test/CIR/CodeGen/struct.cpp b/clang/test/CIR/CodeGen/struct.cpp
index 96db82a89977c..becbce19e63bc 100644
--- a/clang/test/CIR/CodeGen/struct.cpp
+++ b/clang/test/CIR/CodeGen/struct.cpp
@@ -183,3 +183,31 @@ void generic_selection() {
 // OGCG:   %[[C_ADDR:.*]] = alloca i32, align 4
 // OGCG:   %[[D_ADDR:.*]] = alloca %struct.CompleteS, align 4
 // OGCG:   call void @llvm.memcpy.p0.p0.i64(ptr align 4 %[[D_ADDR]], ptr align 4 %[[A_ADDR]], i64 8, i1 false)
+
+void atomic_init() {
+  _Atomic CompleteS a;
+  __c11_atomic_init(&a, {});
+}
+
+// CIR: cir.func{{.*}} @_Z11atomic_initv()
+// CIR:   %[[A_ADDR:.*]] = cir.alloca !rec_CompleteS, !cir.ptr<!rec_CompleteS>, ["a"]
+// CIR:   %[[ELEM_0_PTR:.*]] = cir.get_member %[[A_ADDR]][0] {name = "a"} : !cir.ptr<!rec_CompleteS> -> !cir.ptr<!s32i>
+// CIR:   %[[CONST_0:.*]] = cir.const #cir.int<0> : !s32i
+// CIR:   cir.store{{.*}} %[[CONST_0]], %[[ELEM_0_PTR]] : !s32i, !cir.ptr<!s32i>
+// CIR:   %[[ELEM_1_PTR:.*]] = cir.get_member %[[A_ADDR]][1] {name = "b"} : !cir.ptr<!rec_CompleteS> -> !cir.ptr<!s8i>
+// CIR:   %[[CONST_0:.*]] = cir.const #cir.int<0> : !s8i
+// CIR:   cir.store{{.*}} %[[CONST_0]], %[[ELEM_1_PTR]] : !s8i, !cir.ptr<!s8i>
+
+// LLVM: define{{.*}} void @_Z11atomic_initv()
+// LLVM:   %[[A_ADDR:.*]] = alloca %struct.CompleteS, i64 1, align 8
+// LLVM:   %[[ELEM_0_PTR:.*]] = getelementptr %struct.CompleteS, ptr %[[A_ADDR]], i32 0, i32 0
+// LLVM:   store i32 0, ptr %[[ELEM_0_PTR]], align 8
+// LLVM:   %[[ELEM_1_PTR:.*]] = getelementptr %struct.CompleteS, ptr %[[A_ADDR]], i32 0, i32 1
+// LLVM:   store i8 0, ptr %[[ELEM_1_PTR]], align 4
+
+// OGCG: define{{.*}} void @_Z11atomic_initv()
+// OGCG:   %[[A_ADDR:.*]] = alloca %struct.CompleteS, align 8
+// OGCG:   %[[ELEM_0_PTR:.*]] = getelementptr inbounds nuw %struct.CompleteS, ptr %[[A_ADDR]], i32 0, i32 0
+// OGCG:   store i32 0, ptr %[[ELEM_0_PTR]], align 8
+// OGCG:   %[[ELEM_1_PTR:.*]] = getelementptr inbounds nuw %struct.CompleteS, ptr %[[A_ADDR]], i32 0, i32 1
+// OGCG:   store i8 0, ptr %[[ELEM_1_PTR]], align 4