Bug 188 - consider adding old-hardware compatibility mode to FPU
Summary: consider adding old-hardware compatibility mode to FPU
Status: CONFIRMED
Alias: None
Product: Libre-SOC's first SoC
Classification: Unclassified
Component: Specification (show other bugs)
Version: unspecified
Hardware: All All
: --- enhancement
Assignee: Luke Kenneth Casson Leighton
URL:
Depends on:
Blocks:
 
Reported: 2020-02-24 23:29 GMT by Jacob Lifshay
Modified: 2020-02-25 00:41 GMT (History)
2 users (show)

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Description Jacob Lifshay 2020-02-24 23:29:38 GMT 
See thread at:
https://lists.freedesktop.org/archives/mesa-dev/2020-February/224144.html

This can be done by either having a mode CSR or by using different instructions.

One particular case is where IEEE specifies that 0.0 * Infinity == NaN, old hardware calculates the result as 0.0 * Infinity == 0.0

Note that we would probably need a new Vulkan extension to support this, since Vulkan specifies following IEEE here (from what I recall).
Comment 1 Luke Kenneth Casson Leighton 2020-02-24 23:59:56 GMT 
good call. hm has the khronos group been alerted, it would be good to keep track.
Comment 2 Jacob Lifshay 2020-02-25 00:41:31 GMT 
(In reply to Luke Kenneth Casson Leighton from comment #1)
> good call. hm has the khronos group been alerted, it would be good to keep
> track.

I would assume that the Khronos group knows or will know about this because it will end up in the list of OpenGL extensions that they track.