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//===-- MathToLibm.cpp - conversion from Math to libm calls ---------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "mlir/Conversion/MathToLibm/MathToLibm.h"
#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/Dialect/Func/IR/FuncOps.h"
#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
#include "mlir/Dialect/Math/IR/Math.h"
#include "mlir/Dialect/Utils/IndexingUtils.h"
#include "mlir/Dialect/Vector/IR/VectorOps.h"
#include "mlir/Dialect/Vector/Utils/VectorUtils.h"
#include "mlir/IR/BuiltinDialect.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/Pass/Pass.h"
#include <optional>
namespace mlir {
#define GEN_PASS_DEF_CONVERTMATHTOLIBM
#include "mlir/Conversion/Passes.h.inc"
} // namespace mlir
using namespace mlir;
namespace {
// Pattern to convert vector operations to scalar operations. This is needed as
// libm calls require scalars.
template <typename Op>
struct VecOpToScalarOp : public OpRewritePattern<Op> {
public:
using OpRewritePattern<Op>::OpRewritePattern;
LogicalResult matchAndRewrite(Op op, PatternRewriter &rewriter) const final;
};
// Pattern to promote an op of a smaller floating point type to F32.
template <typename Op>
struct PromoteOpToF32 : public OpRewritePattern<Op> {
public:
using OpRewritePattern<Op>::OpRewritePattern;
LogicalResult matchAndRewrite(Op op, PatternRewriter &rewriter) const final;
};
// Pattern to convert scalar math operations to calls to libm functions.
// Additionally the libm function signatures are declared.
template <typename Op>
struct ScalarOpToLibmCall : public OpRewritePattern<Op> {
public:
using OpRewritePattern<Op>::OpRewritePattern;
ScalarOpToLibmCall<Op>(MLIRContext *context, StringRef floatFunc,
StringRef doubleFunc, PatternBenefit benefit)
: OpRewritePattern<Op>(context, benefit), floatFunc(floatFunc),
doubleFunc(doubleFunc){};
LogicalResult matchAndRewrite(Op op, PatternRewriter &rewriter) const final;
private:
std::string floatFunc, doubleFunc;
};
} // namespace
template <typename Op>
LogicalResult
VecOpToScalarOp<Op>::matchAndRewrite(Op op, PatternRewriter &rewriter) const {
auto opType = op.getType();
auto loc = op.getLoc();
auto vecType = opType.template dyn_cast<VectorType>();
if (!vecType)
return failure();
if (!vecType.hasRank())
return failure();
auto shape = vecType.getShape();
int64_t numElements = vecType.getNumElements();
Value result = rewriter.create<arith::ConstantOp>(
loc, DenseElementsAttr::get(
vecType, FloatAttr::get(vecType.getElementType(), 0.0)));
SmallVector<int64_t> strides = computeStrides(shape);
for (auto linearIndex = 0; linearIndex < numElements; ++linearIndex) {
SmallVector<int64_t> positions = delinearize(strides, linearIndex);
SmallVector<Value> operands;
for (auto input : op->getOperands())
operands.push_back(
rewriter.create<vector::ExtractOp>(loc, input, positions));
Value scalarOp =
rewriter.create<Op>(loc, vecType.getElementType(), operands);
result =
rewriter.create<vector::InsertOp>(loc, scalarOp, result, positions);
}
rewriter.replaceOp(op, {result});
return success();
}
template <typename Op>
LogicalResult
PromoteOpToF32<Op>::matchAndRewrite(Op op, PatternRewriter &rewriter) const {
auto opType = op.getType();
if (!opType.template isa<Float16Type, BFloat16Type>())
return failure();
auto loc = op.getLoc();
auto f32 = rewriter.getF32Type();
auto extendedOperands = llvm::to_vector(
llvm::map_range(op->getOperands(), [&](Value operand) -> Value {
return rewriter.create<arith::ExtFOp>(loc, f32, operand);
}));
auto newOp = rewriter.create<Op>(loc, f32, extendedOperands);
rewriter.replaceOpWithNewOp<arith::TruncFOp>(op, opType, newOp);
return success();
}
template <typename Op>
LogicalResult
ScalarOpToLibmCall<Op>::matchAndRewrite(Op op,
PatternRewriter &rewriter) const {
auto module = SymbolTable::getNearestSymbolTable(op);
auto type = op.getType();
if (!type.template isa<Float32Type, Float64Type>())
return failure();
auto name = type.getIntOrFloatBitWidth() == 64 ? doubleFunc : floatFunc;
auto opFunc = dyn_cast_or_null<SymbolOpInterface>(
SymbolTable::lookupSymbolIn(module, name));
// Forward declare function if it hasn't already been
if (!opFunc) {
OpBuilder::InsertionGuard guard(rewriter);
rewriter.setInsertionPointToStart(&module->getRegion(0).front());
auto opFunctionTy = FunctionType::get(
rewriter.getContext(), op->getOperandTypes(), op->getResultTypes());
opFunc = rewriter.create<func::FuncOp>(rewriter.getUnknownLoc(), name,
opFunctionTy);
opFunc.setPrivate();
// By definition Math dialect operations imply LLVM's "readnone"
// function attribute, so we can set it here to provide more
// optimization opportunities (e.g. LICM) for backends targeting LLVM IR.
// This will have to be changed, when strict FP behavior is supported
// by Math dialect.
opFunc->setAttr(LLVM::LLVMDialect::getReadnoneAttrName(),
UnitAttr::get(rewriter.getContext()));
}
assert(isa<FunctionOpInterface>(SymbolTable::lookupSymbolIn(module, name)));
rewriter.replaceOpWithNewOp<func::CallOp>(op, name, op.getType(),
op->getOperands());
return success();
}
void mlir::populateMathToLibmConversionPatterns(
RewritePatternSet &patterns, PatternBenefit benefit,
llvm::Optional<PatternBenefit> log1pBenefit) {
patterns.add<VecOpToScalarOp<math::Atan2Op>, VecOpToScalarOp<math::CbrtOp>,
VecOpToScalarOp<math::ExpM1Op>, VecOpToScalarOp<math::TanhOp>,
VecOpToScalarOp<math::CosOp>, VecOpToScalarOp<math::SinOp>,
VecOpToScalarOp<math::ErfOp>, VecOpToScalarOp<math::RoundEvenOp>,
VecOpToScalarOp<math::RoundOp>, VecOpToScalarOp<math::AtanOp>,
VecOpToScalarOp<math::TanOp>, VecOpToScalarOp<math::TruncOp>>(
patterns.getContext(), benefit);
patterns.add<PromoteOpToF32<math::Atan2Op>, PromoteOpToF32<math::CbrtOp>,
PromoteOpToF32<math::ExpM1Op>, PromoteOpToF32<math::TanhOp>,
PromoteOpToF32<math::CosOp>, PromoteOpToF32<math::SinOp>,
PromoteOpToF32<math::ErfOp>, PromoteOpToF32<math::RoundEvenOp>,
PromoteOpToF32<math::RoundOp>, PromoteOpToF32<math::AtanOp>,
PromoteOpToF32<math::TanOp>, PromoteOpToF32<math::TruncOp>>(
patterns.getContext(), benefit);
patterns.add<ScalarOpToLibmCall<math::AtanOp>>(patterns.getContext(), "atanf",
"atan", benefit);
patterns.add<ScalarOpToLibmCall<math::Atan2Op>>(patterns.getContext(),
"atan2f", "atan2", benefit);
patterns.add<ScalarOpToLibmCall<math::CbrtOp>>(patterns.getContext(), "cbrtf",
"cbrt", benefit);
patterns.add<ScalarOpToLibmCall<math::ErfOp>>(patterns.getContext(), "erff",
"erf", benefit);
patterns.add<ScalarOpToLibmCall<math::ExpM1Op>>(patterns.getContext(),
"expm1f", "expm1", benefit);
patterns.add<ScalarOpToLibmCall<math::TanOp>>(patterns.getContext(), "tanf",
"tan", benefit);
patterns.add<ScalarOpToLibmCall<math::TanhOp>>(patterns.getContext(), "tanhf",
"tanh", benefit);
patterns.add<ScalarOpToLibmCall<math::RoundEvenOp>>(
patterns.getContext(), "roundevenf", "roundeven", benefit);
patterns.add<ScalarOpToLibmCall<math::RoundOp>>(patterns.getContext(),
"roundf", "round", benefit);
patterns.add<ScalarOpToLibmCall<math::CosOp>>(patterns.getContext(), "cosf",
"cos", benefit);
patterns.add<ScalarOpToLibmCall<math::SinOp>>(patterns.getContext(), "sinf",
"sin", benefit);
patterns.add<ScalarOpToLibmCall<math::Log1pOp>>(
patterns.getContext(), "log1pf", "log1p", log1pBenefit.value_or(benefit));
patterns.add<ScalarOpToLibmCall<math::FloorOp>>(patterns.getContext(),
"floorf", "floor", benefit);
patterns.add<ScalarOpToLibmCall<math::CeilOp>>(patterns.getContext(), "ceilf",
"ceil", benefit);
patterns.add<ScalarOpToLibmCall<math::TruncOp>>(patterns.getContext(),
"truncf", "trunc", benefit);
}
namespace {
struct ConvertMathToLibmPass
: public impl::ConvertMathToLibmBase<ConvertMathToLibmPass> {
void runOnOperation() override;
};
} // namespace
void ConvertMathToLibmPass::runOnOperation() {
auto module = getOperation();
RewritePatternSet patterns(&getContext());
populateMathToLibmConversionPatterns(patterns, /*benefit=*/1);
ConversionTarget target(getContext());
target.addLegalDialect<arith::ArithDialect, BuiltinDialect, func::FuncDialect,
vector::VectorDialect>();
target.addIllegalDialect<math::MathDialect>();
if (failed(applyPartialConversion(module, target, std::move(patterns))))
signalPassFailure();
}
std::unique_ptr<OperationPass<ModuleOp>> mlir::createConvertMathToLibmPass() {
return std::make_unique<ConvertMathToLibmPass>();
}
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