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Spec: Finalise behaviour of MP instructions #23

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ben-marshall opened this issue Sep 25, 2018 · 0 comments
Closed
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Spec: Finalise behaviour of MP instructions #23

ben-marshall opened this issue Sep 25, 2018 · 0 comments
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question Further information is requested specification Issue relates to the XCrypto ISE specification
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ben-marshall commented Sep 25, 2018 •
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We haven't quite finalised how some of the MP instructions should behave, mainly wrt which bits some treat as carry in/carry out.

sub2/sub3

  • These don't seem to make sense in their current form. Would they be better formulated as a "deaccumulate"?

equ/ltu/gtu

  • I don't know exactly what sort of comparison these instructions are performing. I think they just need the individual carry bits stating.
  • I suspect these will need renaming.

Shift Instructions

  • Change spec so that the high word of the 64 bit result goes to destination register 2. Not only is this more sensible, it makes implementation easier as well.
  • See issue Spec: MP Shift destination register order. #24 for more information.
@ben-marshall ben-marshall added the question Further information is requested label Sep 25, 2018
@ben-marshall ben-marshall added this to the Version 1.0a milestone Sep 27, 2018
@ben-marshall ben-marshall added the specification Issue relates to the XCrypto ISE specification label Sep 27, 2018
ben-marshall added a commit that referenced this issue Oct 15, 2018
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MP Instruction Implementation Work
2a99de1 
- See #14, #7, #23, #30
- Re-implemented all existing MALU RTL.
- All previously implemented instruction unit tests passing.
- Adding unit test for `sub2.mp`
- Added ISE model for `sub2.mp`
- Need to add unit tests for `sub3`, `mac` and comparison instructions.
- Only RTL left to implement is for comparison instructions.

 On branch dev/ben-marshall
 Changes to be committed:
	modified:   docs/implementation.tex
	modified:   flow/icarus/waves-view.gtkw
	modified:   rtl/coprocessor/scarv_cop_malu.v
	modified:   verif/model/model_ise.v
	modified:   verif/unit/21-add3-mp.S
	new file:   verif/unit/28-sub2-mp.S
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