[Bug middle-end/121249] New: build_constant_desc has some obvious dead code in it

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121249

            Bug ID: 121249
           Summary: build_constant_desc has some obvious dead code in it
           Product: gcc
           Version: 14.2.0
            Status: UNCONFIRMED
          Keywords: internal-improvement
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

build_constant_desc does:
```
  /* Construct the VAR_DECL associated with the constant.  */
  decl = build_decl (UNKNOWN_LOCATION, VAR_DECL, get_identifier (label),
                     TREE_TYPE (exp));
...
  DECL_IN_CONSTANT_POOL (decl) = 1;
...


      int align = (TREE_CODE (decl) == CONST_DECL
                   || (VAR_P (decl) && DECL_IN_CONSTANT_POOL (decl))
                   ? DECL_ALIGN (decl)
                   : symtab_node::get (decl)->definition_alignment ());
```

So `VAR_P (decl) && DECL_IN_CONSTANT_POOL (decl)` will always be true as
nothing modifies the tree code nor DECL_IN_CONSTANT_POOL after building/setting
them.

This dead code was added with r5-7630-g7185ec2cb42ab0. I think it was a search
and replace of DECL_ALIGN (decl) and not noticing that `VAR_P (decl) &&
DECL_IN_CONSTANT_POOL (decl)` would always be true here.