This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: using scratchpads to enhance RTL-level if-conversion: revised patch
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: Richard Henderson <rth at redhat dot com>
- Cc: gcc-patches at gcc dot gnu dot org, Bernd Schmidt <bschmidt at redhat dot com>, Abe <abe_skolnik at yahoo dot com>, Sebastian Pop <sebpop at gmail dot com>, Kyrill Tkachov <kyrylo dot tkachov at arm dot com>
- Date: Wed, 14 Oct 2015 10:28:04 +0200
- Subject: Re: using scratchpads to enhance RTL-level if-conversion: revised patch
- Authentication-results: sourceware.org; auth=none
- References: <5615AADE dot 4030306 at yahoo dot com> <56166E68 dot 2040004 at redhat dot com> <561DAA48 dot 60604 at redhat dot com>
> If you're using one of the switches that checks for stack overflow at the
> start of the function, you certainly don't want to do any such stores.
There is a protection area for -fstack-check (STACK_CHECK_PROTECT bytes) so
you can do stores just below the stack pointer as far as it's concerned.
There is indeed the issue of the mere writing below the stack pointer. Our
experience with various OSes and architectures shows that this almost always
works. The only problematic case is x86{-64}/Linux historically, where you
cannot write below the page pointed to by the stack pointer (that's why there
is a specific implementation of -fstack-check for x86{-64}/Linux).
--
Eric Botcazou