[Lldb-commits] [PATCH] D113498: [lldb] Constant-resolve operands to `getelementptr`

[Andy Yankovsky via Phabricator via lldb-commits]

werat added a comment.

In D113498#3139112 <https://reviews.llvm.org/D113498#3139112>, @shafik wrote:

> On the other hand this is a well-formed constant expression:
>
>   static const int x =0;
>   constexpr const int* ip1 = &x + 1;
>
> Does that get you the test case you need?

This expression seems to be similar to what I have in the test case now.

  (lldb) p static const int x = 0; constexpr const int* ip1 = &x + 1;
  ...
  ; Function Attrs: convergent noinline nounwind optnone
  define dso_local void @"?$__lldb_expr@@YAXPEAX at Z"(i8* %"$__lldb_arg") #0 {
  entry:
    %"$__lldb_arg.addr" = alloca i8*, align 8, !clang.decl.ptr !9
    %ip1 = alloca i32*, align 8, !clang.decl.ptr !10
    store i8* %"$__lldb_arg", i8** %"$__lldb_arg.addr", align 8
    store i32* bitcast (i8* getelementptr (i8, i8* bitcast (i32* @"?x@?1??$__lldb_expr@@YAXPEAX at Z@4HB" to i8*), i64 4) to i32*), i32** %ip1, align 8
    ret void
  }

As far as I understand, `getelementptr (i8, i8* bitcast (i32* @"?x@?1??$__lldb_expr@@YAXPEAX at Z@4HB" to i8*), i64 4)` is a well-formed constant expression, however it has `GlobalVariableVal` as one of it's operand. Even though `GlobalVariableVal` is `Constant`, I think it's not always possible to resolve its value (please correct me if that's not true, not very familiar with IR). Even if there's a way, it's not currently implemented in the IRInterpreter -- `CanResolveConstant` will return false when it sees `GlobalVariableVal`.


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https://reviews.llvm.org/D113498