27d9a479c0
In the context of C/Fortran interoperability (BIND(C)), it is possible to give the VALUE attribute to a BIND(C) derived type dummy, which according to Fortran 2018 18.3.6 - 2. (4) implies that it must be passed like the equivalent C structure value. The way C structure value are passed is ABI dependent. LLVM does not implement the C struct ABI passing for LLVM aggregate type arguments. It is up to the front-end, like clang is doing, to split the struct into registers or pass the struct on the stack (llvm "byval") as required by the target ABI. So the logic for C struct passing sits in clang. Using it from flang requires setting up a lot of clang context and to bridge FIR/MLIR representation to clang AST representation for function signatures (in both directions). It is a non trivial task. See https://stackoverflow.com/questions/39438033/passing-structs-by-value-in-llvm-ir/75002581#75002581. Since BIND(C) struct are rather limited as opposed to generic C struct (e.g. no bit fields). It is easier to provide a limited implementation of it for the case that matter to Fortran. This patch: - Updates the generic target rewrite pass to keep track of both the new argument type and attributes. The motivation for this is to be able to tell if a previously marshalled argument is passed in memory (it is a C pointer), or if it is being passed on the stack (has the byval llvm attributes). - Adds an entry point in the target specific codegen to marshal struct arguments, and use it in the generic target rewrite pass. - Implements limited support for the X86-64 case. So far, the support allows telling if a struct must be passed in register or on the stack, and to deal with the stack case. The register case is left TODO in this patch. The X86-64 ABI implemented is the System V ABI for AMD64 version 1.0
61 lines
2.4 KiB
C++
61 lines
2.4 KiB
C++
//===-- Optimizer/Support/DataLayout.cpp ----------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "flang/Optimizer/Support/DataLayout.h"
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#include "flang/Optimizer/Dialect/Support/FIRContext.h"
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#include "flang/Optimizer/Support/FatalError.h"
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#include "mlir/Dialect/DLTI/DLTI.h"
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#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
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#include "mlir/IR/BuiltinOps.h"
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#include "mlir/Interfaces/DataLayoutInterfaces.h"
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#include "mlir/Support/LLVM.h"
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#include "mlir/Target/LLVMIR/Import.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/MC/TargetRegistry.h"
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#include "llvm/Support/TargetSelect.h"
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#include "llvm/Target/TargetMachine.h"
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void fir::support::setMLIRDataLayout(mlir::ModuleOp mlirModule,
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const llvm::DataLayout &dl) {
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mlir::MLIRContext *context = mlirModule.getContext();
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mlirModule->setAttr(
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mlir::LLVM::LLVMDialect::getDataLayoutAttrName(),
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mlir::StringAttr::get(context, dl.getStringRepresentation()));
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mlir::DataLayoutSpecInterface dlSpec = mlir::translateDataLayout(dl, context);
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mlirModule->setAttr(mlir::DLTIDialect::kDataLayoutAttrName, dlSpec);
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}
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void fir::support::setMLIRDataLayoutFromAttributes(mlir::ModuleOp mlirModule,
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bool allowDefaultLayout) {
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if (mlirModule.getDataLayoutSpec())
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return; // Already set.
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if (auto dataLayoutString = mlirModule->getAttrOfType<mlir::StringAttr>(
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mlir::LLVM::LLVMDialect::getDataLayoutAttrName())) {
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llvm::DataLayout llvmDataLayout(dataLayoutString);
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fir::support::setMLIRDataLayout(mlirModule, llvmDataLayout);
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return;
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}
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if (!allowDefaultLayout)
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return;
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llvm::DataLayout llvmDataLayout("");
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fir::support::setMLIRDataLayout(mlirModule, llvmDataLayout);
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}
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std::optional<mlir::DataLayout>
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fir::support::getOrSetDataLayout(mlir::ModuleOp mlirModule,
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bool allowDefaultLayout) {
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if (!mlirModule.getDataLayoutSpec()) {
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fir::support::setMLIRDataLayoutFromAttributes(mlirModule,
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allowDefaultLayout);
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if (!mlirModule.getDataLayoutSpec()) {
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return std::nullopt;
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}
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}
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return mlir::DataLayout(mlirModule);
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}
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