circt::synth::CutRewriter Class Reference

Main cut-based rewriting algorithm for combinational logic optimization. More...

#include <CutRewriter.h>

Collaboration diagram for circt::synth::CutRewriter:

Public Member Functions
	CutRewriter (const CutRewriterOptions &options, CutRewritePatternSet &patterns)
	Constructor for the cut rewriter.
LogicalResult	run (Operation *topOp)
	Execute the complete cut-based rewriting algorithm.

Private Member Functions
LogicalResult	enumerateCuts (Operation *topOp)
	Enumerate cuts for all nodes in the given module.
ArrayRef< std::pair< NPNClass, const CutRewritePattern * > >	getMatchingPatternsFromTruthTable (const Cut &cut) const
	Find patterns that match a cut's truth table.
std::optional< MatchedPattern >	patternMatchCut (const Cut &cut)
	Match a cut against available patterns and compute arrival time.
LogicalResult	runBottomUpRewrite (Operation *topOp)
	Perform the actual circuit rewriting using selected patterns.

Private Attributes
const CutRewriterOptions &	options
	Configuration options.
const CutRewritePatternSet &	patterns
	Available rewriting patterns.
CutEnumerator	cutEnumerator

Detailed Description

Main cut-based rewriting algorithm for combinational logic optimization.

The CutRewriter implements a cut-based rewriting algorithm that:

1. Enumerates cuts in the combinational logic network using a priority cuts algorithm
2. Matches cuts against available rewriting patterns
3. Selects optimal patterns based on area or timing objectives
4. Rewrites the circuit using the selected patterns

The algorithm processes the network in topological order, building up cut sets for each node and selecting the best implementation based on the specified optimization strategy.

Usage example:

CutRewriterOptions options;
options.strategy = OptimizationStrategy::Area;
options.maxCutInputSize = 4;
options.maxCutSizePerRoot = 8;
 
CutRewritePatternSet patterns(std::move(optimizationPatterns));
CutRewriter rewriter(module, options, patterns);
 
if (failed(rewriter.run())) {
  // Handle rewriting failure
}

Definition at line 456 of file CutRewriter.h.

Constructor & Destructor Documentation

CutRewriter()

circt::synth::CutRewriter::CutRewriter ( const CutRewriterOptions &  options, CutRewritePatternSet &  patterns  )

inline

Constructor for the cut rewriter.

Definition at line 459 of file CutRewriter.h.

Member Function Documentation

enumerateCuts()

LogicalResult CutRewriter::enumerateCuts ( Operation *  topOp )

private

Enumerate cuts for all nodes in the given module.

Note: This preserves module boundaries and does not perform rewriting across the hierarchy.

Definition at line 906 of file CutRewriter.cpp.

References cutEnumerator, circt::synth::CutEnumerator::enumerateCuts(), and patternMatchCut().

Referenced by run().

getMatchingPatternsFromTruthTable()

ArrayRef< std::pair< NPNClass, const CutRewritePattern * > > CutRewriter::getMatchingPatternsFromTruthTable ( const Cut &  cut ) const

private

Find patterns that match a cut's truth table.

Definition at line 917 of file CutRewriter.cpp.

References circt::synth::Cut::getNPNClass().

Referenced by patternMatchCut().

patternMatchCut()

std::optional< MatchedPattern > CutRewriter::patternMatchCut ( const Cut &  cut )

private

Match a cut against available patterns and compute arrival time.

Definition at line 929 of file CutRewriter.cpp.

References assert(), compareDelayAndArea(), cutEnumerator, circt::synth::Cut::dump(), circt::synth::CutRewritePattern::getArea(), circt::synth::CutEnumerator::getCutSet(), circt::NPNClass::getInputPermutation(), circt::synth::Cut::getInputSize(), getMatchingPatternsFromTruthTable(), circt::synth::Cut::getNPNClass(), circt::synth::Cut::getOutputSize(), circt::synth::Cut::inputs, isAlwaysCutInput(), circt::synth::Cut::isTrivialCut(), options, pattern, and circt::synth::CutRewriterOptions::strategy.

Referenced by enumerateCuts().

run()

LogicalResult CutRewriter::run

(

Operation *

topOp

)

Execute the complete cut-based rewriting algorithm.

This method orchestrates the entire rewriting process:

1. Enumerate cuts for all nodes in the combinational logic
2. Match cuts against available patterns
3. Select optimal patterns based on strategy
4. Rewrite the circuit with selected patterns

Definition at line 861 of file CutRewriter.cpp.

References cutEnumerator, circt::synth::CutEnumerator::dump(), enumerateCuts(), circt::synth::CutRewriterOptions::maxCutInputSize, circt::synth::CutRewriterOptions::maxCutSizePerRoot, circt::synth::OptimizationStrategyArea, options, pattern, runBottomUpRewrite(), circt::synth::CutRewriterOptions::strategy, circt::synth::CutRewriterOptions::testPriorityCuts, and circt::synth::topologicallySortLogicNetwork().

Referenced by GenericLUTMapperPass::runOnOperation().

runBottomUpRewrite()

LogicalResult CutRewriter::runBottomUpRewrite ( Operation *  topOp )

private

Perform the actual circuit rewriting using selected patterns.

Definition at line 1042 of file CutRewriter.cpp.

References circt::synth::CutRewriterOptions::allowNoMatch, circt::synth::CutRewriterOptions::attachDebugTiming, circt::synth::CutEnumerator::clear(), cutEnumerator, circt::UnusedOpPruner::eraseNow(), isAlwaysCutInput(), options, and circt::synth::CutEnumerator::takeVector().

Referenced by run().

Member Data Documentation

cutEnumerator

CutEnumerator circt::synth::CutRewriter::cutEnumerator

private

Definition at line 493 of file CutRewriter.h.

Referenced by enumerateCuts(), patternMatchCut(), run(), and runBottomUpRewrite().

options

const CutRewriterOptions& circt::synth::CutRewriter::options

private

Configuration options.

Definition at line 488 of file CutRewriter.h.

Referenced by patternMatchCut(), run(), and runBottomUpRewrite().

patterns

const CutRewritePatternSet& circt::synth::CutRewriter::patterns

private

Available rewriting patterns.

Definition at line 491 of file CutRewriter.h.

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The documentation for this class was generated from the following files:

• /home/runner/work/circt-www/circt-www/circt_src/include/circt/Dialect/Synth/Transforms/CutRewriter.h
• /home/runner/work/circt-www/circt-www/circt_src/lib/Dialect/Synth/Transforms/CutRewriter.cpp