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Re: [PATCH, rs6000] Fixing PR 67145
- From: Richard Henderson <rth at redhat dot com>
- To: Segher Boessenkool <segher at kernel dot crashing dot org>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Alan Modra <amodra at gmail dot com>, David Edelsohn <dje dot gcc at gmail dot com>
- Date: Fri, 26 Feb 2016 13:35:10 -0800
- Subject: Re: [PATCH, rs6000] Fixing PR 67145
- Authentication-results: sourceware.org; auth=none
- References: <56CFDDD0 dot 6030503 at redhat dot com> <20160226210311 dot GD32075 at gate dot crashing dot org>
On 02/26/2016 01:03 PM, Segher Boessenkool wrote:
> On Thu, Feb 25, 2016 at 09:08:32PM -0800, Richard Henderson wrote:
>> + /* Perform rematerialization if only all operands are registers and
>> + all operations are PLUS. */
>> + for (i = 0; i < n_ops; i++)
>> + if (ops[i].neg || !REG_P (ops[i].op))
>> + return NULL_RTX;
>> + goto gen_result;
>> + }
>
> If you check for fixed registers as well here, does that work for you?
Maybe. It prevents canonicalization of reg+fp vs fp+reg, which could well
occur via arithmetic on locally allocated arrays.
I guess for the purposes of stage4 I'd be willing to do
if (ops[i].neg
|| !REG_P (ops[i].op)
|| (REGNO (ops[i].op) < FIRST_PSEUDO_REGISTER
&& fixed_regs[REGNO (ops[i].op)]
&& !global_regs[REGNO (ops[i].op)]
&& ops[i].op != frame_pointer_rtx
&& ops[i].op != arg_pointer_rtx
&& ops[i].op != stack_pointer_rtx))
It's pretty ugly though, and I wouldn't want to keep this forever.
The rs6000 change really ought to be evaluated at some point. Given its scope,
I see little difference to doing that now vs putting it off to gcc7.
r~