On Tue, 9 Oct 2018, Tamar Christina wrote: > Hi All, > > I'm looking for permission to backport this patch to the GCC-8 branch > to fix PR86486. > > OK for backport?
This doesn't seem to fix a regression and it's been on trunk only for a few days. Richard. > Thanks, > Tamar > > > -----Original Message----- > > From: Jeff Law <l...@redhat.com> > > Sent: Wednesday, July 11, 2018 19:53 > > To: Tamar Christina <tamar.christ...@arm.com>; gcc-patches@gcc.gnu.org > > Cc: nd <n...@arm.com>; rguent...@suse.de; i...@airs.com > > Subject: Re: [PATCH][GCC][mid-end] Add a hook to support telling the mid- > > end when to probe the stack [patch (2/6)] > > > > On 07/11/2018 05:21 AM, Tamar Christina wrote: > > > Hi All, > > > > > > This patch adds a hook to tell the mid-end about the probing > > > requirements of the target. On AArch64 we allow a specific range for > > > which no probing needs to be done. This same range is also the amount > > > that will have to be probed up when a probe is needed after dropping the > > stack. > > > > > > Defining this probe comes with the extra requirement that the outgoing > > > arguments size of any function that uses alloca and stack clash be at > > > the very least 8 bytes. With this invariant we can skip doing the > > > zero checks for alloca and save some code. > > > > > > A simplified version of the AArch64 stack frame is: > > > > > > +-----------------------+ > > > | | > > > | | > > > | | > > > +-----------------------+ > > > |LR | > > > +-----------------------+ > > > |FP | > > > +-----------------------+ > > > |dynamic allocations | -\ probe range hook effects these > > > +-----------------------+ --\ and ensures that outgoing stack > > > |padding | -- args is always > 8 when alloca. > > > +-----------------------+ ---/ Which means it's always safe to probe > > > |outgoing stack args |-/ at SP > > > +-----------------------+ > > > > > > > > > This allows us to generate better code than without the hook without > > > affecting other targets. > > > > > > With this patch I am also removing the > > > stack_clash_protection_final_dynamic_probe > > > hook which was added specifically for AArch64 but that is no longer > > > needed. > > > > > > Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-pc-linux-gnu > > and no issues. > > > Both targets were tested with stack clash on and off by default. > > > > > > Ok for trunk? > > > > > > Thanks, > > > Tamar > > > > > > gcc/ > > > 2018-07-11 Tamar Christina <tamar.christ...@arm.com> > > > > > > PR target/86486 > > > * explow.c (anti_adjust_stack_and_probe_stack_clash): Support > > custom > > > probe ranges. > > > * target.def (stack_clash_protection_alloca_probe_range): New. > > > (stack_clash_protection_final_dynamic_probe): Remove. > > > * targhooks.h (default_stack_clash_protection_alloca_probe_range) > > New. > > > (default_stack_clash_protection_final_dynamic_probe): Remove. > > > * targhooks.c: Likewise. > > > * doc/tm.texi.in > > (TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE): New. > > > (TARGET_STACK_CLASH_PROTECTION_FINAL_DYNAMIC_PROBE): > > Remove. > > > * doc/tm.texi: Regenerate. > > > > > The control flow is a bit convoluted here, but after a few false starts > > where I > > thought this was wrong, I think it's OK. > > > > Jeff > > > > > > > > > > > > > > > > > > > > -- Richard Biener <rguent...@suse.de> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)
