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[circt-lec] Fixed equivalence check for multiple outputs #5358

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Jun 27, 2023
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[circt-lec] Fixed equivalence check for multiple outputs #5358

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25 changes: 25 additions & 0 deletions integration_test/circt-lec/hw.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -40,3 +40,28 @@ hw.module @notnot(%in: i1) -> (out: i1) {
// hw.output
// RUN: circt-lec %s -c1=basic -c2=basic -v=false | FileCheck %s --check-prefix=HW_OUTPUT
// HW_OUTPUT: c1 == c2


hw.module @constZeroZero(%in: i1) -> (o1: i1, o2: i1) {
%zero = hw.constant 0 : i1
hw.output %zero, %zero : i1, i1
}

hw.module @xorZeroZero(%in: i1) -> (o1: i1, o2: i1) {
%zero = comb.xor bin %in, %in : i1
hw.output %zero, %zero : i1, i1
}

hw.module @constZeroOne(%in: i1) -> (o1: i1, o2: i1) {
%zero = hw.constant 0 : i1
%one = hw.constant 1 : i1
hw.output %zero, %one : i1, i1
}

// Equivalent modules with two outputs
// RUN: circt-lec %s -c1=constZeroZero -c2=xorZeroZero -v=false | FileCheck %s --check-prefix=TWOOUTPUTS
// TWOOUTPUTS: c1 == c2

// Modules with one equivalent and one non-equivalent output
// RUN: not circt-lec %s -c1=constZeroZero -c2=constZeroOne -v=false | FileCheck %s --check-prefix=TWOOUTPUTSFAIL
// TWOOUTPUTSFAIL: c1 != c2
7 changes: 6 additions & 1 deletion lib/LogicalEquivalence/Solver.cpp
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Expand Up @@ -173,6 +173,8 @@ LogicalResult Solver::constrainCircuits() {
return failure();
}

z3::expr_vector outputTerms(context);

const auto *c1outIt = c1Outputs.begin();
const auto *c2outIt = c2Outputs.begin();
for (unsigned i = 0; i < nc1Outputs; i++) {
Expand All @@ -182,8 +184,11 @@ LogicalResult Solver::constrainCircuits() {
return failure();
}
// Their ith outputs have to be equivalent.
solver.add(*c1outIt++ != *c2outIt++);
outputTerms.push_back(*c1outIt++ != *c2outIt++);
}

// The circuits are not equivalent iff any of the outputs is not equal
solver.add(z3::mk_or(outputTerms));

return success();
}