[clang] Add CodeGen tests for CWG 5xx issues (#84303)

This patch covers [CWG519](https://cplusplus.github.io/CWG/issues/519.html) "Null pointer preservation in `void*` conversions", [CWG571](https://cplusplus.github.io/CWG/issues/571.html) "References declared const".
llvm · Mar 7, 2024 · 4157217 · 4157217
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diff --git a/clang/test/CXX/drs/dr519.cpp b/clang/test/CXX/drs/dr519.cpp
@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -std=c++98 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++11 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++14 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++17 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++20 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++23 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++2c %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+
+namespace dr519 { // dr519: 2.7
+void f() {
+  int *a = 0;
+  void *v = a;
+  bool c1 = v == static_cast<void *>(0);
+
+  void *w = 0;
+  int *b = static_cast<int*>(w);
+  bool c2 = b == static_cast<int *>(0);
+}
+} // namespace dr519
+
+// We're checking that `null`s that were initially stored in `a` and `w`
+// are simply copied over all the way to respective comparisons with `null`.
+
+// CHECK-LABEL: define {{.*}} void @dr519::f()()
+// CHECK:         store ptr null, ptr [[A:%.+]],
+// CHECK-NEXT:    [[TEMP_A:%.+]] = load ptr, ptr [[A]] 
+// CHECK-NEXT:    store ptr [[TEMP_A]], ptr [[V:%.+]],
+// CHECK-NEXT:    [[TEMP_V:%.+]] = load ptr, ptr [[V]]
+// CHECK-NEXT:    {{.+}} = icmp eq ptr [[TEMP_V]], null
+
+// CHECK:         store ptr null, ptr [[W:%.+]],
+// CHECK-NEXT:    [[TEMP_W:%.+]] = load ptr, ptr [[W]] 
+// CHECK-NEXT:    store ptr [[TEMP_W]], ptr [[B:%.+]],
+// CHECK-NEXT:    [[TEMP_B:%.+]] = load ptr, ptr [[B]]
+// CHECK-NEXT:    {{.+}} = icmp eq ptr [[TEMP_B]], null
+// CHECK-LABEL: }
diff --git a/clang/test/CXX/drs/dr571.cpp b/clang/test/CXX/drs/dr571.cpp
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -std=c++98 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++11 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++14 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++17 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++20 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++23 %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+// RUN: %clang_cc1 -std=c++2c %s -triple x86_64-linux-gnu -emit-llvm -o - -fexceptions -fcxx-exceptions -pedantic-errors | llvm-cxxfilt -n | FileCheck %s --check-prefixes CHECK
+
+namespace dr571 { // dr571: 2.7
+  typedef int &ir;
+  int n;
+  const ir r = n;
+  // expected-warning@-1 {{'const' qualifier on reference type 'ir' (aka 'int &') has no effect}}
+  ir r2 = n;
+}
+
+// Entities have external linkage by default.
+
+// CHECK: @dr571::r = constant ptr @dr571::n
+// CHECK: @dr571::r2 = constant ptr @dr571::n
diff --git a/clang/test/CXX/drs/dr5xx.cpp b/clang/test/CXX/drs/dr5xx.cpp
@@ -141,15 +141,7 @@ namespace dr518 { // dr518: yes c++11
   // cxx98-error@-1 {{commas at the end of enumerator lists are a C++11 extension}}
 }
 
-namespace dr519 { // dr519: yes
-// FIXME: Add a codegen test.
-#if __cplusplus >= 201103L
-#define fold(x) (__builtin_constant_p(x) ? (x) : (x))
-  int test[fold((int*)(void*)0) ? -1 : 1];
-#undef fold
-#endif
-}
-
+// dr519 is in dr519.cpp
 // dr520: na
 
 // dr521: no
@@ -800,14 +792,7 @@ namespace dr570 { // dr570: dup 633
   //   expected-note@#dr570-r {{previous definition is here}}
 }
 
-namespace dr571 { // dr571 unknown
-  // FIXME: Add a codegen test.
-  typedef int &ir;
-  int n;
-  // FIXME: Test if this has internal linkage.
-  const ir r = n;
-  // expected-warning@-1 {{'const' qualifier on reference type 'ir' (aka 'int &') has no effect}}
-}
+// dr571 is in dr571.cpp
 
 namespace dr572 { // dr572: yes
   enum E { a = 1, b = 2 };

diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
@@ -3154,7 +3154,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/519.html">519</a></td>
     <td>CD1</td>
     <td>Null pointer preservation in <TT>void*</TT> conversions</td>
-    <td class="full" align="center">Yes</td>
+    <td class="full" align="center">Clang 2.7</td>
   </tr>
   <tr id="520">
     <td><a href="https://cplusplus.github.io/CWG/issues/520.html">520</a></td>
@@ -3468,7 +3468,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
     <td><a href="https://cplusplus.github.io/CWG/issues/571.html">571</a></td>
     <td>CD2</td>
     <td>References declared <TT>const</TT></td>
-    <td class="unknown" align="center">Unknown</td>
+    <td class="full" align="center">Clang 2.7</td>
   </tr>
   <tr id="572">
     <td><a href="https://cplusplus.github.io/CWG/issues/572.html">572</a></td>