CIRCT 20.0.0git
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LowerComb.cpp
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1//===- LowerComb.cpp - Lower some ops in comb -------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
12#include "mlir/Transforms/DialectConversion.h"
13#include "llvm/ADT/TypeSwitch.h"
14
15using namespace circt;
16using namespace circt::comb;
17
18namespace circt {
19namespace comb {
20#define GEN_PASS_DEF_LOWERCOMB
21#include "circt/Dialect/Comb/Passes.h.inc"
22} // namespace comb
23} // namespace circt
24
25namespace {
26/// Lower truth tables to mux trees.
27struct TruthTableToMuxTree : public OpConversionPattern<TruthTableOp> {
28 using OpConversionPattern::OpConversionPattern;
29
30private:
31 /// Get a mux tree for `inputs` corresponding to the given truth table. Do
32 /// this recursively by dividing the table in half for each input.
33 // NOLINTNEXTLINE(misc-no-recursion)
34 Value getMux(Location loc, OpBuilder &b, Value t, Value f,
35 ArrayRef<bool> table, Operation::operand_range inputs) const {
36 assert(table.size() == (1ull << inputs.size()));
37 if (table.size() == 1)
38 return table.front() ? t : f;
39
40 size_t half = table.size() / 2;
41 Value if1 =
42 getMux(loc, b, t, f, table.drop_front(half), inputs.drop_front());
43 Value if0 =
44 getMux(loc, b, t, f, table.drop_back(half), inputs.drop_front());
45 return b.create<MuxOp>(loc, inputs.front(), if1, if0, false);
46 }
47
48public:
49 LogicalResult matchAndRewrite(TruthTableOp op, OpAdaptor adaptor,
50 ConversionPatternRewriter &b) const override {
51 Location loc = op.getLoc();
52 SmallVector<bool> table(
53 llvm::map_range(op.getLookupTableAttr().getAsValueRange<IntegerAttr>(),
54 [](const APInt &a) { return !a.isZero(); }));
55 Value t = b.create<hw::ConstantOp>(loc, b.getIntegerAttr(b.getI1Type(), 1));
56 Value f = b.create<hw::ConstantOp>(loc, b.getIntegerAttr(b.getI1Type(), 0));
57
58 Value tree = getMux(loc, b, t, f, table, op.getInputs());
59 b.modifyOpInPlace(tree.getDefiningOp(), [&]() {
60 tree.getDefiningOp()->setDialectAttrs(op->getDialectAttrs());
61 });
62 b.replaceOp(op, tree);
63 return success();
64 }
65};
66} // namespace
67
68namespace {
69class LowerCombPass : public impl::LowerCombBase<LowerCombPass> {
70public:
71 using LowerCombBase::LowerCombBase;
72
73 void runOnOperation() override;
74};
75} // namespace
76
77void LowerCombPass::runOnOperation() {
78 ModuleOp module = getOperation();
79
80 ConversionTarget target(getContext());
81 RewritePatternSet patterns(&getContext());
82 target.markUnknownOpDynamicallyLegal([](Operation *) { return true; });
83 target.addIllegalOp<TruthTableOp>();
84
85 patterns.add<TruthTableToMuxTree>(patterns.getContext());
86
87 if (failed(applyPartialConversion(module, target, std::move(patterns))))
88 return signalPassFailure();
89}
assert(baseType &&"element must be base type")
create(data_type, value)
Definition hw.py:433
The InstanceGraph op interface, see InstanceGraphInterface.td for more details.
Definition comb.py:1