[CIR][CIRGen] Emit constant global _Atomic's

Author: bcardosolopes

clang/lib/CIR/CodeGen/CIRGenExprConst.cpp

@@ -1675,7 +1675,22 @@ mlir::Attribute ConstantEmitter::emitForMemory(CIRGenModule &CGM,
                                                QualType destType) {
   // For an _Atomic-qualified constant, we may need to add tail padding.
   if (auto AT = destType->getAs<AtomicType>()) {
-    assert(0 && "not implemented");
+    QualType destValueType = AT->getValueType();
+    C = emitForMemory(CGM, C, destValueType);
+
+    uint64_t innerSize = CGM.getASTContext().getTypeSize(destValueType);
+    uint64_t outerSize = CGM.getASTContext().getTypeSize(destType);
+    if (innerSize == outerSize)
+      return C;
+
+    assert(innerSize < outerSize && "emitted over-large constant for atomic");
+    auto &builder = CGM.getBuilder();
+    auto zeroArray = builder.getZeroInitAttr(
+        mlir::cir::ArrayType::get(builder.getContext(), builder.getUInt8Ty(),
+                                  (outerSize - innerSize) / 8));
+    SmallVector<mlir::Attribute, 4> anonElts = {C, zeroArray};
+    auto arrAttr = mlir::ArrayAttr::get(builder.getContext(), anonElts);
+    return builder.getAnonConstStruct(arrAttr, false);
   }
 
   // Zero-extend bool.

clang/test/CIR/CodeGen/c11atomic.c

@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 %s -triple aarch64-none-linux-android21 -fclangir -emit-cir -std=c11 -o %t.cir
+// RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
+// RUN: %clang_cc1 %s -triple aarch64-none-linux-android21 -fclangir -emit-llvm -std=c11 -o %t.ll
+// RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
+
+// CIR-DAG: ![[PS:.*]] = !cir.struct<struct "PS" {!cir.int<s, 16>, !cir.int<s, 16>, !cir.int<s, 16>}
+// CIR-DAG: ![[ANON:.*]] = !cir.struct<struct  {!cir.struct<struct "PS" {!cir.int<s, 16>, !cir.int<s, 16>, !cir.int<s, 16>} {{.*}}>, !cir.array<!cir.int<u, 8> x 2>}>
+// CIR-DAG: cir.global external @testPromotedStructGlobal = #cir.const_struct<{#cir.const_struct<{#cir.int<1> : !s16i, #cir.int<2> : !s16i, #cir.int<3> : !s16i}> : ![[PS]], #cir.zero : !cir.array<!u8i x 2>}> : ![[ANON]]
+
+// LLVM-DAG: %[[PS:.*]] = type { i16, i16, i16 }
+// LLVM-DAG: @testPromotedStructGlobal = global { %[[PS]], [2 x i8] } { %[[PS]] { i16 1, i16 2, i16 3 }, [2 x i8] zeroinitializer }
+typedef struct { short x, y, z; } PS;
+_Atomic PS testPromotedStructGlobal = (PS){1, 2, 3};