From: Luke Kenneth Casson Leighton Date: Mon, 16 Sep 2019 06:45:46 +0000 (+0100) Subject: add clarification X-Git-Tag: convert-csv-opcode-to-binary~4047 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=24f7acc797a2a4bfaa926c7310491ee72d07d36f;p=libreriscv.git add clarification --- diff --git a/zfpacc_proposal.mdwn b/zfpacc_proposal.mdwn index b8371d348..96cdc8e2f 100644 --- a/zfpacc_proposal.mdwn +++ b/zfpacc_proposal.mdwn @@ -20,6 +20,20 @@ this proposal. Only ULP (Unit in Last Place) of the instruction *result* is permitted to meet alternative accuracy requirements, whilst still retaining the instruction's requested format. +This proposal is *only* suitable for adding pre-existing accuracy standards +where it is clearly established, well in advance of applications being +written that conform to that standard, that dealing with variations in +accuracy across hardware implementations is the responsibility of the +application writer. This is the case for both Vulkan and OpenCL. + +This proposal is *not* suitable for inclusion of "de-facto" (proprietary) +accuracy standards (historic IBM Mainframe vs Ahmdahl incompatibility) +where there was no prior agreement or notification to applications +writers that variations in accuracy across hardware implementations +would occur. In the unlikely event that they *are* ever to be included +(n the future, rather than as a Custom Extension, then, unlike Vulkan +and OpenCL, they must **only** be added as "bit-for-bit compatible". + # Extension of FCSR Zfpacc would use some of the the reserved bits of FCSR. It would be treated