Hi All, I'm looking for permission to backport this patch to the GCC-8 branch to fix PR86486.
OK for backport? 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 > > > > > > > > >
