[CombToSMT] Make result of div-by-zero undefined #7025
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This adapts the conversion pass to match the recently agreed upon definition for division by zero. Integration tests for circt-lec are added to check the behavior. Note that two syntactically equivalent modules are not considered equivalent if they aren't guaranteed to deterministically produce the same outputs. Alternatively, we could consider two undefined output values equivalent by modeling each value as a pair of a boolean and the bit-vector where the boolean determines if the value is undefined, then two outputs are equivalent if either the boolean is true or the boolean is false and the bitvectors match. There are probably use-cases for both, so maybe we'd want a flag to let the user decide.
TaoBi22
approved these changes
May 13, 2024
Comment on lines
+113
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| auto lecOp = builder.create<verif::LogicEquivalenceCheckingOp>(loc); | ||
| Value areEquivalent = lecOp.getAreEquivalent(); | ||
| builder.cloneRegionBefore(moduleA.getBody(), lecOp.getFirstCircuit(), | ||
| lecOp.getFirstCircuit().end()); | ||
| builder.cloneRegionBefore(moduleB.getBody(), lecOp.getSecondCircuit(), | ||
| lecOp.getSecondCircuit().end()); | ||
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| moduleA->erase(); | ||
| if (moduleA != moduleB) | ||
| moduleB->erase(); | ||
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| { | ||
| OpBuilder::InsertionGuard guard(builder); | ||
| builder.setInsertionPoint(outputOpA); | ||
| builder.create<verif::YieldOp>(loc, outputOpA->getOperands()); | ||
| outputOpA->erase(); | ||
| builder.setInsertionPoint(outputOpB); | ||
| builder.create<verif::YieldOp>(loc, outputOpB->getOperands()); | ||
| outputOpB->erase(); | ||
| } | ||
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| sortTopologically(&lecOp.getFirstCircuit().front()); | ||
| sortTopologically(&lecOp.getSecondCircuit().front()); | ||
| { | ||
| auto *term = lecOp.getFirstCircuit().front().getTerminator(); | ||
| OpBuilder::InsertionGuard guard(builder); | ||
| builder.setInsertionPoint(term); | ||
| builder.create<verif::YieldOp>(loc, term->getOperands()); | ||
| term->erase(); | ||
| term = lecOp.getSecondCircuit().front().getTerminator(); | ||
| builder.setInsertionPoint(term); | ||
| builder.create<verif::YieldOp>(loc, term->getOperands()); | ||
| term->erase(); | ||
| } | ||
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| sortTopologically(&lecOp.getFirstCircuit().front()); | ||
| sortTopologically(&lecOp.getSecondCircuit().front()); | ||
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Is this change just to ensure a module isn't trivially found to be equivalent to itself if its output is undefined?
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This adapts the conversion pass to match the recently agreed upon definition for division by zero. Integration tests for circt-lec are added to check the behavior. Note that two syntactically equivalent modules are not considered equivalent if they aren't guaranteed to deterministically produce the same outputs. Alternatively, we could consider two undefined output values equivalent by modeling each value as a pair of a boolean and the bit-vector where the boolean determines if the value is undefined, then two outputs are equivalent if either the boolean is true or the boolean is false and the bitvectors match. There are probably use-cases for both, so maybe we'd want a flag to let the user decide.