RE: [PATCH] PR tree-optimization/83907: Improved memset handling in strlen pass.

["Roger Sayle" <roger@nextmovesoftware.com>]

Hi Jeff,
Any chance you could take a look at this patch, now that we're back in stage1?
Thanks in advance,
Roger

> -----Original Message-----
> From: Jeff Law <jeffreyalaw@gmail.com>
> Sent: 02 March 2022 19:33
> To: Roger Sayle <roger@nextmovesoftware.com>; gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH] PR tree-optimization/83907: Improved memset handling in
> strlen pass.
> 
> On 2/20/2022 9:51 AM, Roger Sayle wrote:
> > This patch implements the missed optimization enhancement PR 83907, by
> > handling memset with a constant byte value in tree-ssa's strlen
> > optimization pass.  Effectively, this treats memset(dst,'x',3) as it
> > would memcpy(dst,"xxx",3).
> >
> > This patch also includes a tweak to handle_store to address another
> > missed optimization observed in the related test case pr83907-2.c.
> > The consecutive byte stores to memory get coalesced into a vector
> > write of a vector const, but unfortunately tree-ssa-strlen's
> > handle_store didn't previously handle the (unusual) case where the
> > stored "string" starts with a zero byte but also contains non-zero
> > bytes.
> >
> > This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
> > and make -k check with no new failures.  Ok for mainline?
> >
> >
> > 2022-02-20  Roger Sayle  <roger@nextmovesoftware.com>
> >
> > gcc/ChangeLog
> > 	PR tree-optimization/83907
> > 	* tree-ssa-strlen.cc (handle_builtin_memset): Record a strinfo
> > 	for memset with an constant char value.
> > 	(handle_store): Improved handling of stores with a first byte
> > 	of zero, but not storing_all_zeros_p.
> >
> > gcc/testsuite/ChangeLog
> > 	PR tree-optimization/83907
> > 	* gcc.dg/tree-ssa/pr83907-1.c: New test case.
> > 	* gcc.dg/tree-ssa/pr83907-2.c: New test case.
> Deferring to stage1.
> jeff