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Re: [PATCH] Fix PR69951
- From: Richard Biener <rguenther at suse dot de>
- To: James Greenhalgh <james dot greenhalgh at arm dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Tue, 1 Mar 2016 10:21:27 +0100 (CET)
- Subject: Re: [PATCH] Fix PR69951
- Authentication-results: sourceware.org; auth=none
- References: <alpine dot LSU dot 2 dot 11 dot 1602260930480 dot 31547 at t29 dot fhfr dot qr> <20160229173637 dot GA33430 at arm dot com>
On Mon, 29 Feb 2016, James Greenhalgh wrote:
> On Fri, Feb 26, 2016 at 09:32:53AM +0100, Richard Biener wrote:
> >
> > The following fixes PR69951, hopefully the last case of decl alias
> > issues with alias analysis. This time it's points-to and the DECL_UIDs
> > used in points-to sets not being canonicalized.
> >
> > The simplest (and cheapest) fix is to make aliases refer to the
> > ultimate alias target via their DECL_PT_UID which we conveniently
> > have available.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
> >
> > Richard.
> >
> > 2016-02-26 Richard Biener <rguenther@suse.de>
> >
> > PR tree-optimization/69551
> > * tree-ssa-structalias.c (get_constraint_for_ssa_var): When
> > looking through aliases adjust DECL_PT_UID to refer to the
> > ultimate alias target.
> >
> > * gcc.dg/torture/pr69951.c: New testcase.
>
> I see this new testcase failing on an ARM target as so:
>
> /tmp/ccChjoFc.s: Assembler messages:
> /tmp/ccChjoFc.s:21: Warning: [-mwarn-syms]: Assignment makes a symbol match an ARM instruction: b
>
> FAIL: gcc.dg/torture/pr69951.c -O0 (test for excess errors)
>
> But I haven't managed to reproduce it outside of the test environment.
>
> The fix looks trivial, rename b to anything else you fancy (well... stay
> clear of add and ldr). I'll put a fix in myself if I can manage to get
> this to reproduce - though if anyone else wants to do it I won't be
> offended :-).
Huh, I wonder what's the use of such warning. After all 'ldr' is a valid
C symbol name, too. In fact my cross arm as doesn't report this
warning (binutils 2.25.0)
> arm-suse-linux-gnueabi-as t.s -mwarn-syms
Assembler messages:
Error: unrecognized option -mwarn-syms
Richard.