On Wed, 2 Nov 2016, Jakub Jelinek wrote:
> On Wed, Nov 02, 2016 at 10:08:25AM +0100, Richard Biener wrote:
> > On Mon, 31 Oct 2016, Jakub Jelinek wrote:
> >
> > > Hi!
> > >
> > > Some automatic VAR_DECLs don't get DECL_RTL set - e.g. if its SSA_NAMEs
> > > expand to multiple rtls, then there is not a single one that can be used.
> > > Using DECL_RTL on such VAR_DECLs ICEs.
> > >
> > > I've tried to just return 0 in nonoverlapping_memrefs_p if either
> > > DECL_RTL_SET_P (expr{x,y}) wasn't true, but that triggered way too often
> > > during bootstrap/regtest (3800+ times). So the following patch narrows it
> > > down more and triggers only on the testcase below.
> >
> > What kind of cases did this trigger on? I would have expected we
> > have DECL_RTL_SET_P on (almost?) all decls that can have it. And for
> > those that don't it should be uninteresting to have?
>
> I admit I havne't studied it in detail yet. Attaching list of
> BITS_PER_WORD, main_input_filename, current_function_name ()
> where nonoverlapping_memrefs_p returned 0 early because
> either exprx or expry didn't have DECL_RTL_SET_P. As except for the new
> testcase that didn't result into ICE, all of those must have been something
> where make_decl_rtl created RTL in that case.
Ok, just looking at regex.c (I happen to have regex.i around) shows
the first hit as
#2 0x00000000008d9914 in true_dependence_1 (mem=0x7ffff61ef360,
mem_mode=DImode, mem_addr=0x7ffff6220cf0, x=0x7ffff6605060,
x_addr=0x7ffff662ffd8, mem_canonicalized=true)
at /space/rguenther/src/svn/trunk/gcc/alias.c:2928
2928 if (nonoverlapping_memrefs_p (mem, x, false))
(gdb) p debug_tree (expry)
<function_decl 0x7ffff6941f00 __builtin_malloc
type <function_type 0x7ffff68b0dc8
2928 if (nonoverlapping_memrefs_p (mem, x, false))
(gdb) p debug_rtx (mem)
(mem/f/c:DI (plus:DI (reg/f:DI 7 sp)
(const_int 200 [0xc8])) [5 p+0 S8 A64])
$4 = void
(gdb) p debug_rtx (x)
(mem:QI (symbol_ref:DI ("malloc") [flags 0x41] <function_decl
0x7ffff6943000 malloc>) [0 __builtin_malloc S1 A8])
$5 = void
called from DSE check_mem_read_rtx. I believe that's a bogus query.
(I see only a single hit on regex.c, your log seems to have multiple
ones...)
I wouldn't worry about the lost cases, and if I'd be ambitious I'd
try to investigate the above and see what remains...
> > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
> >
> > Hmm. Can you try splitting out a decl_can_have_rtl () predicate
> > from make_decl_rtl and use that?
>
> Will do.
Thanks,
Richard.
