Add muldiv_c and muxadd peepopts
#4740
Open
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
povik
requested changes
Nov 14, 2024
| std::swap(add_a, add_b); | ||
| endcode | ||
|
|
||
| match mux |
There was a problem hiding this comment.
We can also match on the case of swapped mux inputs
passes/pmgen/peepopt_muxadd.pmg
Outdated
| match mux | ||
| // Select mux of form s ? (a + b) : a, allow leading 0s when A_WIDTH != Y_WIDTH | ||
| select mux->type == $mux | ||
| index <SigSpec> port(mux, \A) === SigSpec({Const(State::S0, GetSize(add_y)-GetSize(add_a)), add_a}) |
There was a problem hiding this comment.
This should be zero-padded if !param(add, \A_SIGNED).bool() and sign-extended otherwise (provided add_a is the A input)
There was a problem hiding this comment.
Also I am not sure this doesn't crash on add_y < add_a which I don't think we rule out anywhere
| mux->setPort(\A, Const(State::S0, GetSize(add_b))); | ||
| mux->setPort(\B, add_b); | ||
| mux->setPort(\Y, mid); | ||
| add->setPort(\B, mid); |
There was a problem hiding this comment.
Wrong side of the adder if the swap above was hit (we need to use add_a_id instead)
|
Thanks for the feedback on |
povik
reviewed
Nov 15, 2024
| std::swap(a, b_const); | ||
| endcode | ||
|
|
||
| match div |
There was a problem hiding this comment.
No check that the divider and multiplier are connected
Co-authored-by: Martin Povišer <[email protected]>
Co-authored-by: Martin Povišer <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
What are the reasons/motivation for this change?
This PR adds two peep-hole optimizations that improve netlist quality:
muldiv_c:y = (a * b_const) / c_const ===> a * eval(b_const / c_const)ifb_const % c_const == 0. This implements basic constant propagation for multipliers and dividers with divisible constants.muxadd:y = s ? (a + b) : a ===> y = a + (s ? b : 0). This provides useful restructuring for improving logic optimization.s ? b : 0can be optimized to a bitwise AND in subsequent optimizations.Explain how this is achieved.
passes/pmgen/peepopt_muldiv_c.pmg:muldiv_cpeepoptpasses/pmgen/peepopt_muxadd.pmg:muxaddpeepoptpasses/pmgen/peepopt.cc: Add to docs and run peepopts duringpeepoptpasspasses/pmgen/Makefile.inc: Add the new sourcesIf applicable, please suggest to reviewers how they can test the change.
equiv_optor FOSSeqy