Re: [PATCH 3/3] combine: initialize a local var

[Vineet Gupta <vineetg@rivosinc.com>]

On 5/3/24 01:26, Segher Boessenkool wrote:
> On Thu, May 02, 2024 at 11:59:24AM -0700, Vineet Gupta wrote:
>> This is no logic change (but technically still a functional change).
> Where are 1/3 and 2/3?  Or are those unrelated? 

Yes they were unrelated (minor doc fixes) hence didn't want to spam you,
but you are right just because they were piled up in my spring cleaning
branch doesn't mean I send them out that way.

> Please don't make series like that.

Noted for future.

>
>> Ran into this when stepping thru combine code.
>> @newpat has some random garbage for a bit until it is actually set.
>> With the fix it remains 0 until actually set.
> The same is true for all uninitialised variables.  Setting everything
> to zero explicitly is a) quite a bit slower, and b) just as wrong!
> For example, here, newpat should never be zero.  Never.  It does not
> make any sense.
>
> Is there any place where newpat is used uninitialised?

As I mentioned this patch was the outcome of my "debugging" experience
and agree I should not conflate between what the compiler does and what
is needed to debug the compiler itself.

I've dropped this one.

Thx,
-Vineet