Bug 106

Summary:	pipeline early-in, early-out on concurrent function units
Product:	Libre-SOC's first SoC	Reporter:	Luke Kenneth Casson Leighton <lkcl>
Component:	ALU (including IEEE754 16/32/64-bit FPU)	Assignee:	Luke Kenneth Casson Leighton <lkcl>
Status:	CONFIRMED ---
Severity:	enhancement	CC:	libre-soc-bugs
Priority:	---
Version:	unspecified
Hardware:	PC
OS:	Linux
NLnet milestone:	---	total budget (EUR) for completion of task and all subtasks:	0
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Bug Depends on:
Bug Blocks:	102, 114

Description Luke Kenneth Casson Leighton 2019-06-29 15:45:43 BST

the FP ALUs need to be re-useable for INT computation, by allowing
early-in (bypassing normalisation), getting at what would normally
be just the mantissa part of the pipeline, and jumping out.

whilst early-out is easy (due to the muxid), early-in may be challenging.
the simplest method, although it has the strong disadvantage of creating
unnecessary latency, is to just feed in the operands at the front of
the pipeline.

however, a timing-critical method of bringing the muxids from the later
stages up to the front (the Reservation Station) may also work.