regrename: don't overflow insn_rr_info

Ramana Radhakrishnan
Fri Nov 6 11:34:00 GMT 2015

On 06/11/15 11:31, Bernd Schmidt wrote:
> On 11/06/2015 12:17 PM, Ramana Radhakrishnan wrote:
>> On 06/11/15 11:08, Bernd Schmidt wrote:
>>> This one is a fix for something that could currently only affect c6x, but I have code that exposes it on i386.
>>> When optionally gathering operand info in regrename, we can overflow the array in certain situations. This can occur when we have a situation where a value is constructed in multiple small registers and then accessed as a larger one (CDImode in the testcase I have). In that case we enter the "superset" path, which fails the involved chains, but the smaller pieces still all get seen by record_operand_use, and there may be more of them than MAX_REGS_PER_ADDRESS.
>>> The following fixes it. Bootstrapped and tested  with -frename-registers enabled at -O1 on x86_64-linux. Ok?
>>> Bernd
>> This sounds like it will fix ...
> Ah, I didn't realize something else was using this functionality:
> gcc/config/aarch64/cortex-a57-fma-steering.c
> 1025:  regrename_init (true);
> Yeah, the description of that bug makes it sound like the same issue.

Yeah looks like the ICE goes away with a quick spin - I've not done any deeper analysis but that looks like a fix.

I'll take the opportunity to point out gcc11{3-6} if you need an aarch64 machine on the compile farm if you wanted access to one.


> Bernd

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