[clang] [C2y] Implement WG14 N3369 and N3469 (_Countof) (PR #133125)

[Aaron Ballman via cfe-commits]

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@@ -0,0 +1,92 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
+// RUN: %clang_cc1 -std=c2y -emit-llvm -o - %s | FileCheck %s
+
+// This tests the codegen behavior for _Countof.
+// CHECK-LABEL: define dso_local i32 @test1(
+// CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[ARRAY:%.*]] = alloca [12 x i32], align 16
+// CHECK-NEXT:    ret i32 12
+//
+int test1() {
+  int array[12];
+  return _Countof(array);
+}
+
+// CHECK-LABEL: define dso_local i32 @test2(
+// CHECK-SAME: i32 noundef [[N:%.*]]) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[N_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    [[SAVED_STACK:%.*]] = alloca ptr, align 8
+// CHECK-NEXT:    [[__VLA_EXPR0:%.*]] = alloca i64, align 8
+// CHECK-NEXT:    store i32 [[N]], ptr [[N_ADDR]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i32, ptr [[N_ADDR]], align 4
+// CHECK-NEXT:    [[TMP1:%.*]] = zext i32 [[TMP0]] to i64
+// CHECK-NEXT:    [[TMP2:%.*]] = call ptr @llvm.stacksave.p0()
+// CHECK-NEXT:    store ptr [[TMP2]], ptr [[SAVED_STACK]], align 8
+// CHECK-NEXT:    [[VLA:%.*]] = alloca i32, i64 [[TMP1]], align 16
+// CHECK-NEXT:    store i64 [[TMP1]], ptr [[__VLA_EXPR0]], align 8
+// CHECK-NEXT:    [[CONV:%.*]] = trunc i64 [[TMP1]] to i32
+// CHECK-NEXT:    [[TMP3:%.*]] = load ptr, ptr [[SAVED_STACK]], align 8
+// CHECK-NEXT:    call void @llvm.stackrestore.p0(ptr [[TMP3]])
+// CHECK-NEXT:    ret i32 [[CONV]]
+//
+int test2(int n) {
+  int array[n];
+  return _Countof(array);
+}
+
+// CHECK-LABEL: define dso_local i32 @test3(
+// CHECK-SAME: i32 noundef [[N:%.*]]) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[N_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store i32 [[N]], ptr [[N_ADDR]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i32, ptr [[N_ADDR]], align 4
+// CHECK-NEXT:    [[TMP1:%.*]] = zext i32 [[TMP0]] to i64
+// CHECK-NEXT:    [[CONV:%.*]] = trunc i64 [[TMP1]] to i32
+// CHECK-NEXT:    ret i32 [[CONV]]
+//
+int test3(int n) {
+  return _Countof(int[n]);
+}
+
+// CHECK-LABEL: define dso_local i32 @test4(
+// CHECK-SAME: ) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    ret i32 100
+//
+int test4() {
+  return _Countof(float[100]);
+}
+
+// CHECK-LABEL: define dso_local i32 @test5(
+// CHECK-SAME: i32 noundef [[N:%.*]]) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[N_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    [[SAVED_STACK:%.*]] = alloca ptr, align 8
+// CHECK-NEXT:    [[__VLA_EXPR0:%.*]] = alloca i64, align 8
+// CHECK-NEXT:    [[X:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    [[Y:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store i32 [[N]], ptr [[N_ADDR]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i32, ptr [[N_ADDR]], align 4
+// CHECK-NEXT:    [[TMP1:%.*]] = zext i32 [[TMP0]] to i64
+// CHECK-NEXT:    [[TMP2:%.*]] = call ptr @llvm.stacksave.p0()
+// CHECK-NEXT:    store ptr [[TMP2]], ptr [[SAVED_STACK]], align 8
+// CHECK-NEXT:    [[VLA:%.*]] = alloca [7 x i32], i64 [[TMP1]], align 16
+// CHECK-NEXT:    store i64 [[TMP1]], ptr [[__VLA_EXPR0]], align 8
+// CHECK-NEXT:    [[CONV:%.*]] = trunc i64 [[TMP1]] to i32
+// CHECK-NEXT:    store i32 [[CONV]], ptr [[X]], align 4
+// CHECK-NEXT:    store i32 7, ptr [[Y]], align 4
+// CHECK-NEXT:    [[TMP3:%.*]] = load i32, ptr [[X]], align 4
+// CHECK-NEXT:    [[TMP4:%.*]] = load i32, ptr [[Y]], align 4
+// CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[TMP3]], [[TMP4]]
+// CHECK-NEXT:    [[TMP5:%.*]] = load ptr, ptr [[SAVED_STACK]], align 8
+// CHECK-NEXT:    call void @llvm.stackrestore.p0(ptr [[TMP5]])
+// CHECK-NEXT:    ret i32 [[ADD]]
+//
+int test5(int n) {
+  int array[n][7];
+  int x = _Countof(array);
+  int y = _Countof(*array);
+  return x + y;
+}
----------------
AaronBallman wrote:

Good call, this has the same bug as the earlier test regarding what is and isn't an operand resulting in a constant expression.

https://github.com/llvm/llvm-project/pull/133125