a0d699a8e6
This helps to disambiguate accesses in the caller and the callee after LLVM inlining in some apps. I did not see any performance changes, but this is one step towards enabling other optimizations in the apps that I am looking at. The definition of llvm.noalias says: ``` ... indicates that memory locations accessed via pointer values based on the argument or return value are not also accessed, during the execution of the function, via pointer values not based on the argument or return value. This guarantee only holds for memory locations that are modified, by any means, during the execution of the function. ``` I believe this exactly matches Fortran rules for the dummy arguments that are modified during their subprogram execution. I also set llvm.noalias and llvm.nocapture on the !fir.box<> arguments, because the corresponding descriptors cannot be captured and cannot alias anything (not based on them) during the execution of the subprogram.
113 lines
4.5 KiB
C++
113 lines
4.5 KiB
C++
//===- FunctionAttr.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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//===----------------------------------------------------------------------===//
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/// \file
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/// This is a generic pass for adding attributes to functions.
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//===----------------------------------------------------------------------===//
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#include "flang/Optimizer/Dialect/FIROpsSupport.h"
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#include "flang/Optimizer/Support/InternalNames.h"
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#include "flang/Optimizer/Transforms/Passes.h"
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#include "mlir/Dialect/LLVMIR/LLVMAttrs.h"
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#include "mlir/Dialect/LLVMIR/LLVMDialect.h"
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namespace fir {
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#define GEN_PASS_DEF_FUNCTIONATTR
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#include "flang/Optimizer/Transforms/Passes.h.inc"
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} // namespace fir
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#define DEBUG_TYPE "func-attr"
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namespace {
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class FunctionAttrPass : public fir::impl::FunctionAttrBase<FunctionAttrPass> {
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public:
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FunctionAttrPass(const fir::FunctionAttrOptions &options) : Base{options} {}
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FunctionAttrPass() = default;
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void runOnOperation() override;
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};
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} // namespace
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void FunctionAttrPass::runOnOperation() {
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LLVM_DEBUG(llvm::dbgs() << "=== Begin " DEBUG_TYPE " ===\n");
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mlir::func::FuncOp func = getOperation();
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LLVM_DEBUG(llvm::dbgs() << "Func-name:" << func.getSymName() << "\n");
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llvm::StringRef name = func.getSymName();
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auto deconstructed = fir::NameUniquer::deconstruct(name);
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bool isFromModule = !deconstructed.second.modules.empty();
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if ((isFromModule || !func.isDeclaration()) &&
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!fir::hasBindcAttr(func.getOperation())) {
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llvm::StringRef nocapture = mlir::LLVM::LLVMDialect::getNoCaptureAttrName();
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llvm::StringRef noalias = mlir::LLVM::LLVMDialect::getNoAliasAttrName();
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mlir::UnitAttr unitAttr = mlir::UnitAttr::get(func.getContext());
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for (auto [index, argType] : llvm::enumerate(func.getArgumentTypes())) {
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bool isNoCapture = false;
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bool isNoAlias = false;
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if (mlir::isa<fir::ReferenceType>(argType) &&
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!func.getArgAttr(index, fir::getTargetAttrName()) &&
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!func.getArgAttr(index, fir::getAsynchronousAttrName()) &&
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!func.getArgAttr(index, fir::getVolatileAttrName())) {
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isNoCapture = true;
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isNoAlias = !fir::isPointerType(argType);
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} else if (mlir::isa<fir::BaseBoxType>(argType)) {
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// !fir.box arguments will be passed as descriptor pointers
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// at LLVM IR dialect level - they cannot be captured,
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// and cannot alias with anything within the function.
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isNoCapture = isNoAlias = true;
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}
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if (isNoCapture && setNoCapture)
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func.setArgAttr(index, nocapture, unitAttr);
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if (isNoAlias && setNoAlias)
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func.setArgAttr(index, noalias, unitAttr);
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}
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}
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mlir::MLIRContext *context = &getContext();
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if (framePointerKind != mlir::LLVM::framePointerKind::FramePointerKind::None)
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func->setAttr("frame_pointer", mlir::LLVM::FramePointerKindAttr::get(
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context, framePointerKind));
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auto llvmFuncOpName =
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mlir::OperationName(mlir::LLVM::LLVMFuncOp::getOperationName(), context);
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if (!instrumentFunctionEntry.empty())
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func->setAttr(mlir::LLVM::LLVMFuncOp::getInstrumentFunctionEntryAttrName(
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llvmFuncOpName),
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mlir::StringAttr::get(context, instrumentFunctionEntry));
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if (!instrumentFunctionExit.empty())
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func->setAttr(mlir::LLVM::LLVMFuncOp::getInstrumentFunctionExitAttrName(
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llvmFuncOpName),
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mlir::StringAttr::get(context, instrumentFunctionExit));
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if (noInfsFPMath)
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func->setAttr(
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mlir::LLVM::LLVMFuncOp::getNoInfsFpMathAttrName(llvmFuncOpName),
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mlir::BoolAttr::get(context, true));
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if (noNaNsFPMath)
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func->setAttr(
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mlir::LLVM::LLVMFuncOp::getNoNansFpMathAttrName(llvmFuncOpName),
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mlir::BoolAttr::get(context, true));
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if (approxFuncFPMath)
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func->setAttr(
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mlir::LLVM::LLVMFuncOp::getApproxFuncFpMathAttrName(llvmFuncOpName),
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mlir::BoolAttr::get(context, true));
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if (noSignedZerosFPMath)
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func->setAttr(
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mlir::LLVM::LLVMFuncOp::getNoSignedZerosFpMathAttrName(llvmFuncOpName),
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mlir::BoolAttr::get(context, true));
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if (unsafeFPMath)
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func->setAttr(
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mlir::LLVM::LLVMFuncOp::getUnsafeFpMathAttrName(llvmFuncOpName),
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mlir::BoolAttr::get(context, true));
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LLVM_DEBUG(llvm::dbgs() << "=== End " DEBUG_TYPE " ===\n");
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}
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