verify that alloca for constexpr local variable has const attribute

Author: Lancern

clang/test/CIR/CodeGen/const-alloca.cpp

@@ -2,6 +2,7 @@
 // RUN: FileCheck --input-file=%t.cir %s
 
 int produce_int();
+void blackbox(const int &);
 
 void local_const_int() {
   const int x = produce_int();
@@ -17,6 +18,15 @@ void param_const_int(const int x) {}
 // CHECK:  %{{.+}} = cir.alloca !s32i, !cir.ptr<!s32i>, ["x", init, const]
 // CHECK: }
 
+void local_constexpr_int() {
+  constexpr int x = 42;
+  blackbox(x);
+}
+
+// CHECK-LABEL: @_Z19local_constexpr_intv
+// CHECK:   %{{.+}} = cir.alloca !s32i, !cir.ptr<!s32i>, ["x", init, const]
+// CHECK: }
+
 struct Foo {
   int a;
   int b;