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OE bit info removed

Ivan 2016-08-22 13:17:15 +03:00
parent 53ac6d98f4
commit 24170e07cc
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Developer-Information.md

@ -29,16 +29,6 @@ Best wishes and happy coding!
## Information
####OE bit
Some instructions contain an optional `OE`(overflow excpetion) flag. We currently do not implement those versions of the instructions. For example we emulate `add`, `addze`, `subfme` but not `addo`, `addzeo`, `subfmo` which are just the prior operations with the `OE` flag set.
This flag writes to the `OV` and `SO` (overflow and summary overflow) bits of the XER (Fixed-Point Exception Register) register. The reason why it's not implemented is that the [GCC code emitter](http://repo.or.cz/w/official-gcc.git/blob_plain/c2c80e70905bc2e5dedf8352588fc8cb10e3ec7d:/gcc/config/rs6000/rs6000.md) does not use these instructions and so we haven't found any PS3 software that uses it.
If we find some software that has some handwritten assembly that use those instructions we'll need to implement it (or just for completeness). A good reference for XER bits can be found in [PowerPC Microprocessor Family: The Programmer's Reference Guide ](https://www-01.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF778525699600741775) chapter 1.3 and other linked references.
Probably something from the [answers to this SO question](http://stackoverflow.com/questions/199333/best-way-to-detect-integer-overflow-in-c-c) is what we could consider.
####Misc
(Some of this information can be deleted, or at least it should be properly organized).
* `sizeof(char)` = 1 (= 8 bits)