Files
concrete/compilers/concrete-compiler/compiler/lib/Dialect/TFHE/Transforms/Optimization.cpp

90 lines
3.0 KiB
C++

// Part of the Concrete Compiler Project, under the BSD3 License with Zama
// Exceptions. See
// https://github.com/zama-ai/concrete-compiler-internal/blob/main/LICENSE.txt
// for license information.
#include <mlir/Dialect/Arith/IR/Arith.h>
#include <mlir/IR/PatternMatch.h>
#include <mlir/Transforms/GreedyPatternRewriteDriver.h>
#include <concretelang/Dialect/TFHE/IR/TFHEOps.h>
#include <concretelang/Dialect/TFHE/Transforms/Transforms.h>
#include <concretelang/Support/Constants.h>
namespace mlir {
namespace concretelang {
namespace {
/// Get the constant integer that the cleartext was created from if it exists.
std::optional<IntegerAttr>
getConstantIntFromCleartextIfExists(mlir::Value cleartext) {
auto constantOp = cleartext.getDefiningOp();
if (constantOp == nullptr)
return {};
if (llvm::isa<arith::ConstantOp>(constantOp)) {
auto constIntToMul = constantOp->getAttrOfType<mlir::IntegerAttr>("value");
if (constIntToMul != nullptr)
return constIntToMul;
}
return {};
}
/// Rewrite a TFHE multiplication with an integer operation as a
/// Zero operation if it's being multiplied with a constant 0, or as
/// a Negate operation if multiplied with a constant -1.
class MulCleartextLweCiphertextOpPattern
: public mlir::OpRewritePattern<mlir::concretelang::TFHE::MulGLWEIntOp> {
public:
MulCleartextLweCiphertextOpPattern(mlir::MLIRContext *context)
: mlir::OpRewritePattern<mlir::concretelang::TFHE::MulGLWEIntOp>(
context, ::mlir::concretelang::DEFAULT_PATTERN_BENEFIT) {}
mlir::LogicalResult
matchAndRewrite(mlir::concretelang::TFHE::MulGLWEIntOp op,
mlir::PatternRewriter &rewriter) const override {
auto cleartext = op.getOperand(1);
auto constIntToMul = getConstantIntFromCleartextIfExists(cleartext);
// Constant integer
if (constIntToMul.has_value()) {
auto toMul = constIntToMul.value().getInt();
if (toMul == 0) {
rewriter.replaceOpWithNewOp<mlir::concretelang::TFHE::ZeroGLWEOp>(
op, op.getResult().getType());
return mlir::success();
}
if (toMul == -1) {
rewriter.replaceOpWithNewOp<mlir::concretelang::TFHE::NegGLWEOp>(
op, op.getResult().getType(), op.getOperand(0));
return mlir::success();
}
}
return mlir::failure();
}
};
/// Optimization pass that should choose more efficient ways of performing
/// crypto operations.
class TFHEOptimizationPass : public TFHEOptimizationBase<TFHEOptimizationPass> {
public:
void runOnOperation() override {
mlir::Operation *op = getOperation();
mlir::RewritePatternSet patterns(op->getContext());
patterns.add<MulCleartextLweCiphertextOpPattern>(op->getContext());
if (mlir::applyPatternsAndFoldGreedily(op, std::move(patterns)).failed()) {
this->signalPassFailure();
}
}
};
} // end anonymous namespace
std::unique_ptr<mlir::OperationPass<>> createTFHEOptimizationPass() {
return std::make_unique<TFHEOptimizationPass>();
}
} // namespace concretelang
} // namespace mlir