[C2y] Claim conformance to WG14 N3254

clang/test/C/C2y/n3254.c

@@ -0,0 +1,149 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
+// RUN: %clang_cc1 -triple=x86_64 -std=c2y %s -emit-llvm -o - | FileCheck %s
+
+/* WG14 N3254: Yes
+ * Accessing byte arrays
+ *
+ * NB: this basically boils down to how LLVM handles TBAA, so the best we can
+ * do for a Clang test is to test that the LLVM IR we pass is reasonable and we
+ * presume that LLVM has the test coverage to ensure that this behavior isn't
+ * regressed.
+ */
+
+struct S {
+  int x;
+  char c;
+  float f;
+};
+
+#define DECL_BUFFER(Ty, Name) alignas(Ty) unsigned char Name[sizeof(Ty)]
+
+// CHECK-LABEL: define dso_local i32 @foo(
+// CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[BUFFER:%.*]] = alloca [12 x i8], align 1
+// CHECK-NEXT:    [[S_PTR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[BUFFER]], i8 0, i64 12, i1 false)
+// CHECK-NEXT:    [[ARRAYDECAY:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER]], i64 0, i64 0
+// CHECK-NEXT:    store ptr [[ARRAYDECAY]], ptr [[S_PTR]], align 8
+// CHECK-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[S_PTR]], align 8
+// CHECK-NEXT:    [[X:%.*]] = getelementptr inbounds [[STRUCT_S:%.*]], ptr [[TMP0]], i32 0, i32 0
+// CHECK-NEXT:    [[TMP1:%.*]] = load i32, ptr [[X]], align 4
+// CHECK-NEXT:    ret i32 [[TMP1]]
+//
+int foo() {
+  DECL_BUFFER(struct S, buffer) = {};
+  struct S *s_ptr = (struct S *)buffer;
+  return s_ptr->x;
+}
+
+// CHECK-LABEL: define dso_local signext i8 @bar(
+// CHECK-SAME: ) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[BUFFER:%.*]] = alloca [12 x i8], align 1
+// CHECK-NEXT:    [[ARRAYDECAY:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER]], i64 0, i64 0
+// CHECK-NEXT:    [[C:%.*]] = getelementptr inbounds [[STRUCT_S:%.*]], ptr [[ARRAYDECAY]], i32 0, i32 1
+// CHECK-NEXT:    store i8 97, ptr [[C]], align 1
+// CHECK-NEXT:    [[ARRAYDECAY1:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER]], i64 0, i64 0
+// CHECK-NEXT:    [[C2:%.*]] = getelementptr inbounds [[STRUCT_S]], ptr [[ARRAYDECAY1]], i32 0, i32 1
+// CHECK-NEXT:    [[TMP0:%.*]] = load i8, ptr [[C2]], align 1
+// CHECK-NEXT:    ret i8 [[TMP0]]
+//
+char bar() {
+  DECL_BUFFER(struct S, buffer);
+  ((struct S *)buffer)->c = 'a';
+  return ((struct S *)buffer)->c;
+}
+
+// CHECK-LABEL: define dso_local float @baz(
+// CHECK-SAME: ) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[BUFFER:%.*]] = alloca [12 x i8], align 1
+// CHECK-NEXT:    [[ARRAYDECAY:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER]], i64 0, i64 0
+// CHECK-NEXT:    [[F:%.*]] = getelementptr inbounds [[STRUCT_S:%.*]], ptr [[ARRAYDECAY]], i32 0, i32 2
+// CHECK-NEXT:    store float 3.000000e+00, ptr [[F]], align 1
+// CHECK-NEXT:    [[ARRAYDECAY1:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER]], i64 0, i64 0
+// CHECK-NEXT:    [[F2:%.*]] = getelementptr inbounds [[STRUCT_S]], ptr [[ARRAYDECAY1]], i32 0, i32 2
+// CHECK-NEXT:    [[TMP0:%.*]] = load float, ptr [[F2]], align 1
+// CHECK-NEXT:    ret float [[TMP0]]
+//
+float baz() {
+  DECL_BUFFER(struct S, buffer);
+  ((struct S *)buffer)->f = 3.0f;
+  return ((const struct S *)buffer)->f;
+}
+
+struct T {
+  DECL_BUFFER(struct S, buffer);
+};
+
+// CHECK-LABEL: define dso_local signext i8 @quux(
+// CHECK-SAME: ) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[T:%.*]] = alloca [[STRUCT_T:%.*]], align 1
+// CHECK-NEXT:    [[S_PTR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[T]], i8 0, i64 12, i1 false)
+// CHECK-NEXT:    [[BUFFER:%.*]] = getelementptr inbounds [[STRUCT_T]], ptr [[T]], i32 0, i32 0
+// CHECK-NEXT:    [[ARRAYDECAY:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER]], i64 0, i64 0
+// CHECK-NEXT:    store ptr [[ARRAYDECAY]], ptr [[S_PTR]], align 8
+// CHECK-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[S_PTR]], align 8
+// CHECK-NEXT:    [[C:%.*]] = getelementptr inbounds [[STRUCT_S:%.*]], ptr [[TMP0]], i32 0, i32 1
+// CHECK-NEXT:    [[TMP1:%.*]] = load i8, ptr [[C]], align 4
+// CHECK-NEXT:    ret i8 [[TMP1]]
+//
+char quux() {
+  struct T t = {};
+  struct S *s_ptr = (struct S *)t.buffer;
+  return s_ptr->c;
+}
+
+// CHECK-LABEL: define dso_local float @quibble(
+// CHECK-SAME: ) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[BUFFER:%.*]] = alloca [12 x i8], align 1
+// CHECK-NEXT:    [[T_PTR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT:    [[S_PTR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[BUFFER]], i8 0, i64 12, i1 false)
+// CHECK-NEXT:    [[ARRAYDECAY:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER]], i64 0, i64 0
+// CHECK-NEXT:    store ptr [[ARRAYDECAY]], ptr [[T_PTR]], align 8
+// CHECK-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[T_PTR]], align 8
+// CHECK-NEXT:    [[BUFFER1:%.*]] = getelementptr inbounds [[STRUCT_T:%.*]], ptr [[TMP0]], i32 0, i32 0
+// CHECK-NEXT:    [[ARRAYDECAY2:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER1]], i64 0, i64 0
+// CHECK-NEXT:    store ptr [[ARRAYDECAY2]], ptr [[S_PTR]], align 8
+// CHECK-NEXT:    [[TMP1:%.*]] = load ptr, ptr [[S_PTR]], align 8
+// CHECK-NEXT:    [[F:%.*]] = getelementptr inbounds [[STRUCT_S:%.*]], ptr [[TMP1]], i32 0, i32 2
+// CHECK-NEXT:    [[TMP2:%.*]] = load float, ptr [[F]], align 4
+// CHECK-NEXT:    ret float [[TMP2]]
+//
+float quibble() {
+  DECL_BUFFER(struct T, buffer) = {};
+  const struct T *t_ptr = (struct T *)buffer;
+  const struct S *s_ptr = (struct S *)t_ptr->buffer;
+  return s_ptr->f;
+}
+
+// CHECK-LABEL: define dso_local i32 @quorble(
+// CHECK-SAME: ) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[BUFFER:%.*]] = alloca [12 x i8], align 1
+// CHECK-NEXT:    [[S_PTR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT:    [[ARRAYDECAY:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER]], i64 0, i64 0
+// CHECK-NEXT:    [[BUFFER1:%.*]] = getelementptr inbounds [[STRUCT_T:%.*]], ptr [[ARRAYDECAY]], i32 0, i32 0
+// CHECK-NEXT:    [[ARRAYDECAY2:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER1]], i64 0, i64 0
+// CHECK-NEXT:    [[X:%.*]] = getelementptr inbounds [[STRUCT_S:%.*]], ptr [[ARRAYDECAY2]], i32 0, i32 0
+// CHECK-NEXT:    store i32 12, ptr [[X]], align 1
+// CHECK-NEXT:    [[ARRAYDECAY3:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER]], i64 0, i64 0
+// CHECK-NEXT:    [[BUFFER4:%.*]] = getelementptr inbounds [[STRUCT_T]], ptr [[ARRAYDECAY3]], i32 0, i32 0
+// CHECK-NEXT:    [[ARRAYDECAY5:%.*]] = getelementptr inbounds [12 x i8], ptr [[BUFFER4]], i64 0, i64 0
+// CHECK-NEXT:    store ptr [[ARRAYDECAY5]], ptr [[S_PTR]], align 8
+// CHECK-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[S_PTR]], align 8
+// CHECK-NEXT:    [[X6:%.*]] = getelementptr inbounds [[STRUCT_S]], ptr [[TMP0]], i32 0, i32 0
+// CHECK-NEXT:    [[TMP1:%.*]] = load i32, ptr [[X6]], align 4
+// CHECK-NEXT:    ret i32 [[TMP1]]
+//
+int quorble() {
+  DECL_BUFFER(struct T, buffer);
+  ((struct S *)((struct T *)buffer)->buffer)->x = 12;
+  const struct S *s_ptr = (struct S *)((struct T *)buffer)->buffer;
+  return s_ptr->x;
+}

clang/www/c_status.html

@@ -1260,7 +1260,7 @@ <h2 id="c2y">C2y implementation status</h2>
     <tr>
       <td>Accessing byte arrays</td>
       <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3254.pdf">N3254</a></td>
-      <td class="unknown" align="center">Unknown</td>
+      <td class="full" align="center">Yes</td>
     </tr>
     <tr>
       <td>Slay some earthly demons I</td>