Re: [PATCH] avoid assuming gimple_call_alloc_size argument is a call (PR 99489)

[David Malcolm <dmalcolm@redhat.com>]

On Fri, 2021-03-12 at 14:52 +0100, Jakub Jelinek via Gcc-patches wrote:
> On Tue, Mar 09, 2021 at 03:07:38PM -0700, Martin Sebor via Gcc-
> patches wrote:
> > The gimple_call_alloc_size() function is documented to "return null
> > when STMT is not a call to a valid allocation function" but the
> > code
> > assumes STMT is a call statement, causing the function to ICE when
> > it isn't.
> > 
> > The attached patch changes the function to fulfill its contract and
> > return null also when STMT isn't a call.  The fix seems obvious to
> > me but I'll wait some time before committing it in case it's not
> > to someone else.
> 
> I think the name of the function suggests that it should be called on
> calls,
> not random stmts.  Currently the function has 3 callers, two of them
> already verify is_gimple_call before calling it and only one doesn't,
> and the stmt will never be NULL.
> So I'd say it would be better to remove the if (!stmt) return
> NULL_TREE;
> from the start of the function and add is_gimple_call (stmt) &&
> in tree-ssa-strlen.c.

Maybe even make it convert it to taking a "const gcall *", so those

  if (is_gimple_call (stmt))
    {
       ...
       if (gimple_call_alloc_size (stmt, ...))
         {
         }
    }

become:

  if (const gcall *call = dyn_cast <const gcall *> (stmt))
    {
       ...
       if (gimple_call_alloc_size (call, ...))
         {
         }

    }

so that the compiler can enforce this requirement via the type system?

Hope this is constructive
Dave