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[CombToSMT] Make result of div-by-zero undefined #7025

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May 14, 2024
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[CombToSMT] Make result of div-by-zero undefined #7025

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72 changes: 68 additions & 4 deletions integration_test/circt-lec/comb.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -59,10 +59,42 @@ hw.module @decomposedAnd(in %in1: i1, in %in2: i1, out out: i1) {
// TODO

// comb.divs
// TODO
// RUN: circt-lec %s -c1=divs_unsafe -c2=divs_unsafe --shared-libs=%libz3 | FileCheck %s --check-prefix=COMB_DIVS_UNSAFE
// RUN: circt-lec %s -c1=divs -c2=divs --shared-libs=%libz3 | FileCheck %s --check-prefix=COMB_DIVS
// COMB_DIVS_UNSAFE: c1 != c2
// COMB_DIVS: c1 == c2

hw.module @divs_unsafe(in %in1: i32, in %in2: i32, out out: i32) {
%0 = comb.divs %in1, %in2 : i32
hw.output %0 : i32
}

hw.module @divs(in %in1: i32, in %in2: i32, out out: i32) {
%0 = hw.constant 0 : i32
%1 = comb.icmp eq %in2, %0 : i32
%2 = comb.divs %in1, %in2 : i32
%3 = comb.mux %1, %0, %2 : i32
hw.output %3 : i32
}

// comb.divu
// TODO
// RUN: circt-lec %s -c1=divu_unsafe -c2=divu_unsafe --shared-libs=%libz3 | FileCheck %s --check-prefix=COMB_DIVU_UNSAFE
// RUN: circt-lec %s -c1=divu -c2=divu --shared-libs=%libz3 | FileCheck %s --check-prefix=COMB_DIVU
// COMB_DIVU_UNSAFE: c1 != c2
// COMB_DIVU: c1 == c2

hw.module @divu_unsafe(in %in1: i32, in %in2: i32, out out: i32) {
%0 = comb.divu %in1, %in2 : i32
hw.output %0 : i32
}

hw.module @divu(in %in1: i32, in %in2: i32, out out: i32) {
%0 = hw.constant 0 : i32
%1 = comb.icmp eq %in2, %0 : i32
%2 = comb.divu %in1, %in2 : i32
%3 = comb.mux %1, %0, %2 : i32
hw.output %3 : i32
}

// comb.extract
// TODO
Expand All @@ -71,10 +103,42 @@ hw.module @decomposedAnd(in %in1: i1, in %in2: i1, out out: i1) {
// TODO

// comb.mods
// TODO
// RUN: circt-lec %s -c1=mods_unsafe -c2=mods_unsafe --shared-libs=%libz3 | FileCheck %s --check-prefix=COMB_MODS_UNSAFE
// RUN: circt-lec %s -c1=mods -c2=mods --shared-libs=%libz3 | FileCheck %s --check-prefix=COMB_MODS
// COMB_MODS_UNSAFE: c1 != c2
// COMB_MODS: c1 == c2

hw.module @mods_unsafe(in %in1: i32, in %in2: i32, out out: i32) {
%0 = comb.mods %in1, %in2 : i32
hw.output %0 : i32
}

hw.module @mods(in %in1: i32, in %in2: i32, out out: i32) {
%0 = hw.constant 0 : i32
%1 = comb.icmp eq %in2, %0 : i32
%2 = comb.mods %in1, %in2 : i32
%3 = comb.mux %1, %0, %2 : i32
hw.output %3 : i32
}

// comb.modu
// TODO
// RUN: circt-lec %s -c1=modu_unsafe -c2=modu_unsafe --shared-libs=%libz3 | FileCheck %s --check-prefix=COMB_MODU_UNSAFE
// RUN: circt-lec %s -c1=modu -c2=modu --shared-libs=%libz3 | FileCheck %s --check-prefix=COMB_MODU
// COMB_MODU_UNSAFE: c1 != c2
// COMB_MODU: c1 == c2

hw.module @modu_unsafe(in %in1: i32, in %in2: i32, out out: i32) {
%0 = comb.modu %in1, %in2 : i32
hw.output %0 : i32
}

hw.module @modu(in %in1: i32, in %in2: i32, out out: i32) {
%0 = hw.constant 0 : i32
%1 = comb.icmp eq %in2, %0 : i32
%2 = comb.modu %in1, %in2 : i32
%3 = comb.mux %1, %0, %2 : i32
hw.output %3 : i32
}

// comb.mul
// RUN: circt-lec %s -c1=mulBy2 -c2=addTwice --shared-libs=%libz3 | FileCheck %s --check-prefix=COMB_MUL
Expand Down
36 changes: 32 additions & 4 deletions lib/Conversion/CombToSMT/CombToSMT.cpp
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Expand Up @@ -192,6 +192,34 @@ struct OneToOneOpConversion : OpConversionPattern<SourceOp> {
}
};

/// Lower the SourceOp to the TargetOp special-casing if the second operand is
/// zero to return a new symbolic value.
template <typename SourceOp, typename TargetOp>
struct DivisionOpConversion : OpConversionPattern<SourceOp> {
using OpConversionPattern<SourceOp>::OpConversionPattern;
using OpAdaptor = typename SourceOp::Adaptor;

LogicalResult
matchAndRewrite(SourceOp op, OpAdaptor adaptor,
ConversionPatternRewriter &rewriter) const override {
Location loc = op.getLoc();
auto type = dyn_cast<smt::BitVectorType>(adaptor.getRhs().getType());
if (!type)
return failure();

auto resultType = OpConversionPattern<SourceOp>::typeConverter->convertType(
op.getResult().getType());
Value zero =
rewriter.create<smt::BVConstantOp>(loc, APInt(type.getWidth(), 0));
Value isZero = rewriter.create<smt::EqOp>(loc, adaptor.getRhs(), zero);
Value symbolicVal = rewriter.create<smt::DeclareFunOp>(loc, resultType);
Value division =
rewriter.create<TargetOp>(loc, resultType, adaptor.getOperands());
rewriter.replaceOpWithNewOp<smt::IteOp>(op, isZero, symbolicVal, division);
return success();
}
};

/// Converts an operation with a variadic number of operands to a chain of
/// binary operations assuming left-associativity of the operation.
template <typename SourceOp, typename TargetOp>
Expand Down Expand Up @@ -236,10 +264,10 @@ void circt::populateCombToSMTConversionPatterns(TypeConverter &converter,
OneToOneOpConversion<ShlOp, smt::BVShlOp>,
OneToOneOpConversion<ShrUOp, smt::BVLShrOp>,
OneToOneOpConversion<ShrSOp, smt::BVAShrOp>,
OneToOneOpConversion<DivSOp, smt::BVSDivOp>,
OneToOneOpConversion<DivUOp, smt::BVUDivOp>,
OneToOneOpConversion<ModSOp, smt::BVSRemOp>,
OneToOneOpConversion<ModUOp, smt::BVURemOp>,
DivisionOpConversion<DivSOp, smt::BVSDivOp>,
DivisionOpConversion<DivUOp, smt::BVUDivOp>,
DivisionOpConversion<ModSOp, smt::BVSRemOp>,
DivisionOpConversion<ModUOp, smt::BVURemOp>,
VariadicToBinaryOpConversion<ConcatOp, smt::ConcatOp>,
VariadicToBinaryOpConversion<AddOp, smt::BVAddOp>,
VariadicToBinaryOpConversion<MulOp, smt::BVMulOp>,
Expand Down
49 changes: 22 additions & 27 deletions lib/Tools/circt-lec/ConstructLEC.cpp
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Expand Up @@ -110,37 +110,32 @@ void ConstructLECPass::runOnOperation() {

builder.createBlock(&entryFunc.getBody());

Value areEquivalent;
if (moduleA == moduleB) {
// Trivially equivalent
areEquivalent =
builder.create<LLVM::ConstantOp>(loc, builder.getI1Type(), 1);
moduleA->erase();
} else {
auto lecOp = builder.create<verif::LogicEquivalenceCheckingOp>(loc);
areEquivalent = lecOp.getAreEquivalent();
auto *outputOpA = moduleA.getBodyBlock()->getTerminator();
auto *outputOpB = moduleB.getBodyBlock()->getTerminator();
lecOp.getFirstCircuit().takeBody(moduleA.getBody());
lecOp.getSecondCircuit().takeBody(moduleB.getBody());

moduleA->erase();
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());

moduleA->erase();
if (moduleA != moduleB)
moduleB->erase();

{
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();
}

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();
}

sortTopologically(&lecOp.getFirstCircuit().front());
sortTopologically(&lecOp.getSecondCircuit().front());

Comment on lines +113 to +138
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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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Yes exactly.

// TODO: we should find a more elegant way of reporting the result than
// already inserting some LLVM here
Value eqFormatString =
Expand Down
24 changes: 20 additions & 4 deletions test/Conversion/CombToSMT/comb-to-smt.mlir
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Expand Up @@ -10,13 +10,29 @@ func.func @test(%a0: !smt.bv<32>, %a1: !smt.bv<32>, %a2: !smt.bv<32>, %a3: !smt.
%arg4 = builtin.unrealized_conversion_cast %a4 : !smt.bv<1> to i1
%arg5 = builtin.unrealized_conversion_cast %a5 : !smt.bv<4> to i4

// CHECK: smt.bv.sdiv [[A0]], [[A1]] : !smt.bv<32>
// CHECK: [[ZERO:%.+]] = smt.bv.constant #smt.bv<0> : !smt.bv<32>
// CHECK-NEXT: [[IS_ZERO:%.+]] = smt.eq [[A1]], [[ZERO]] : !smt.bv<32>
// CHECK-NEXT: [[UNDEF:%.+]] = smt.declare_fun : !smt.bv<32>
// CHECK-NEXT: [[DIV:%.+]] = smt.bv.sdiv [[A0]], [[A1]] : !smt.bv<32>
// CHECK-NEXT: smt.ite [[IS_ZERO]], [[UNDEF]], [[DIV]] : !smt.bv<32>
%0 = comb.divs %arg0, %arg1 : i32
// CHECK-NEXT: smt.bv.udiv [[A0]], [[A1]] : !smt.bv<32>
// CHECK-NEXT: [[ZERO:%.+]] = smt.bv.constant #smt.bv<0> : !smt.bv<32>
// CHECK-NEXT: [[IS_ZERO:%.+]] = smt.eq [[A1]], [[ZERO]] : !smt.bv<32>
// CHECK-NEXT: [[UNDEF:%.+]] = smt.declare_fun : !smt.bv<32>
// CHECK-NEXT: [[DIV:%.+]] = smt.bv.udiv [[A0]], [[A1]] : !smt.bv<32>
// CHECK-NEXT: smt.ite [[IS_ZERO]], [[UNDEF]], [[DIV]] : !smt.bv<32>
%1 = comb.divu %arg0, %arg1 : i32
// CHECK-NEXT: smt.bv.srem [[A0]], [[A1]] : !smt.bv<32>
// CHECK-NEXT: [[ZERO:%.+]] = smt.bv.constant #smt.bv<0> : !smt.bv<32>
// CHECK-NEXT: [[IS_ZERO:%.+]] = smt.eq [[A1]], [[ZERO]] : !smt.bv<32>
// CHECK-NEXT: [[UNDEF:%.+]] = smt.declare_fun : !smt.bv<32>
// CHECK-NEXT: [[DIV:%.+]] = smt.bv.srem [[A0]], [[A1]] : !smt.bv<32>
// CHECK-NEXT: smt.ite [[IS_ZERO]], [[UNDEF]], [[DIV]] : !smt.bv<32>
%2 = comb.mods %arg0, %arg1 : i32
// CHECK-NEXT: smt.bv.urem [[A0]], [[A1]] : !smt.bv<32>
// CHECK-NEXT: [[ZERO:%.+]] = smt.bv.constant #smt.bv<0> : !smt.bv<32>
// CHECK-NEXT: [[IS_ZERO:%.+]] = smt.eq [[A1]], [[ZERO]] : !smt.bv<32>
// CHECK-NEXT: [[UNDEF:%.+]] = smt.declare_fun : !smt.bv<32>
// CHECK-NEXT: [[DIV:%.+]] = smt.bv.urem [[A0]], [[A1]] : !smt.bv<32>
// CHECK-NEXT: smt.ite [[IS_ZERO]], [[UNDEF]], [[DIV]] : !smt.bv<32>
%3 = comb.modu %arg0, %arg1 : i32

// CHECK-NEXT: [[NEG:%.+]] = smt.bv.neg [[A1]] : !smt.bv<32>
Expand Down
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