[clang] [clang] Add some CodeGen tests for CWG 4xx issues (PR #83715)

[Erich Keane via cfe-commits]

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@@ -0,0 +1,24 @@
+// 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 dr438 { // dr438: 2.7
+
+void f() {
+  long A[2];
+  A[0] = 0;
+  A[A[0]] = 1;
+}
+
+} // namespace dr438
+
+// CHECK-LABEL: define {{.*}} void @dr438::f()()
+// CHECK:         [[A:%.+]] = alloca [2 x i64]
+// CHECK:         [[ARRAYIDX1:%.+]] = getelementptr inbounds [2 x i64], ptr [[A]], i64 0, i64 0
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erichkeane wrote:

We should probably match the FIRST GEP/Store here too.  Else ARRAYIDX1 could end up being the 'first' GEP (to do the `A[0] = 0` store).

https://github.com/llvm/llvm-project/pull/83715