Re: Accessing IP on IA-64 with RTL

[James E Wilson <wilson at specifixinc dot com>]

On Mon, 2005-01-31 at 14:20, Steve Ellcey wrote:
> I don't think the existing mcount can be called after the prologue.

I took a look at glibc.  You are right.  The current assembly stub has
too many assumptions built into it.  I think it would work if we called
__mcount directly instead of via the stub, but we can't do that
apparently because it isn't exported in the linker map.  I'll have to
see if I can get modified glibc built to try this.  If we can do this
with a linker map change, then we keep backwards compatibility with
older compilers.  I don't know the hazards of changing the linker map
though.  Or maybe __mcount can be renamed to mcount, which is being
exported, and then continue using _mcount for the assembly stub.

> Here is what I have so far, it works with HP-UX based on some minimal
> testing, but is obviously broken for the existing Linux mcount
> interface.

It looks pretty reasonable.  It would be nice if we could continue
supporting the current working linux mcount code, which means continuing
to use FUNCTION_PROFILER for linux while using PROFILE_HOOK for HPUX. 
This requires making a bunch of changes conditional on the OS.  The
glibc issue may not be fixed for a while.

Meanwhile, maybe we can work around the assembly issue by modifying
FUNCTION_PROFILER to emit some unwind directives.  You don't need to
worry about that though, as it isn't needed for HPUX.

> + static GTY(()) rtx mcount_func_rtx;
> + static rtx
> + gen_mcount_func_rtx (void)
> + {

You are missing an explanatory comment before this function, though I
see the ones you copied from are also similarly broken.

The ia64_profile_hook function is also missing a comment.

The ia64.md file change has an unnecessary blank line.
-- 
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com