[fpc-devel] x86 TEST instruction

Stefan Glienke sglienke at dsharp.org
Thu Jun 30 19:07:18 CEST 2022

Both clang and gcc seem to do this

> On 30/06/2022 17:28 CEST J. Gareth Moreton via fpc-devel <fpc-devel at lists.freepascal.org> wrote:
> This was what I was working on:
> https://gitlab.com/freepascal.org/fpc/source/-/merge_requests/252
> The same question applies regarding the TEST instruction, but it's a 
> little more restrictive in this instance in that it's determined that 
> the program doesn't care about the upper bytes of the register once the 
> optimisation is made, so "testl $1,%ebx" is indeed the same as "testb 
> $1,%bl" due to previous logic, but I am wondering if a penalty might be 
> incurred due to the partial read or if this is only a concern for 
> partial writes.
> Gareth aka. Kit
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