ca50be8c89
NVPTXAliasAnalysis extends the default AA to take pointer address spaces into account. The analysis assumes that pointers in different address spaces do not alias, unless one of them is generic (flat) address space. The patch also implements pointsToConstantMemory (via getModRefInfoMask) to expose semantic of the constant address space to the optimizer as discussed in D112466. Differential Revision: https://reviews.llvm.org/D124787
99 lines
3.5 KiB
C++
99 lines
3.5 KiB
C++
//===--------------------- NVPTXAliasAnalysis.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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/// \file
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/// This is the NVPTX address space based alias analysis pass.
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//===----------------------------------------------------------------------===//
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#include "NVPTXAliasAnalysis.h"
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#include "MCTargetDesc/NVPTXBaseInfo.h"
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#include "NVPTX.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/CallingConv.h"
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#include "llvm/IR/Instructions.h"
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using namespace llvm;
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#define DEBUG_TYPE "NVPTX-aa"
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AnalysisKey NVPTXAA::Key;
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char NVPTXAAWrapperPass::ID = 0;
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char NVPTXExternalAAWrapper::ID = 0;
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INITIALIZE_PASS(NVPTXAAWrapperPass, "nvptx-aa",
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"NVPTX Address space based Alias Analysis", false, true)
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INITIALIZE_PASS(NVPTXExternalAAWrapper, "nvptx-aa-wrapper",
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"NVPTX Address space based Alias Analysis Wrapper", false, true)
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ImmutablePass *llvm::createNVPTXAAWrapperPass() {
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return new NVPTXAAWrapperPass();
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}
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ImmutablePass *llvm::createNVPTXExternalAAWrapperPass() {
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return new NVPTXExternalAAWrapper();
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}
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NVPTXAAWrapperPass::NVPTXAAWrapperPass() : ImmutablePass(ID) {
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initializeNVPTXAAWrapperPassPass(*PassRegistry::getPassRegistry());
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}
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void NVPTXAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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}
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static AliasResult::Kind getAliasResult(unsigned AS1, unsigned AS2) {
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if ((AS1 == ADDRESS_SPACE_GENERIC) || (AS2 == ADDRESS_SPACE_GENERIC))
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return AliasResult::MayAlias;
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// PTX s6.4.1.1. Generic Addressing:
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// A generic address maps to global memory unless it falls within
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// the window for const, local, or shared memory. The Kernel
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// Function Parameters (.param) window is contained within the
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// .global window.
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//
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// Therefore a global pointer may alias with a param pointer on some
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// GPUs via addrspacecast(param->generic->global) when cvta.param
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// instruction is used (PTX 7.7+ and SM_70+).
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//
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// TODO: cvta.param is not yet supported. We need to change aliasing
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// rules once it is added.
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return (AS1 == AS2 ? AliasResult::MayAlias : AliasResult::NoAlias);
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}
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AliasResult NVPTXAAResult::alias(const MemoryLocation &Loc1,
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const MemoryLocation &Loc2, AAQueryInfo &AAQI,
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const Instruction *) {
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unsigned AS1 = Loc1.Ptr->getType()->getPointerAddressSpace();
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unsigned AS2 = Loc2.Ptr->getType()->getPointerAddressSpace();
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return getAliasResult(AS1, AS2);
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}
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// TODO: .param address space may be writable in presence of cvta.param, but
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// this instruction is currently not supported. NVPTXLowerArgs also does not
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// allow any writes to .param pointers.
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static bool isConstOrParam(unsigned AS) {
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return AS == AddressSpace::ADDRESS_SPACE_CONST ||
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AS == AddressSpace::ADDRESS_SPACE_PARAM;
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}
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ModRefInfo NVPTXAAResult::getModRefInfoMask(const MemoryLocation &Loc,
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AAQueryInfo &AAQI,
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bool IgnoreLocals) {
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if (isConstOrParam(Loc.Ptr->getType()->getPointerAddressSpace()))
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return ModRefInfo::NoModRef;
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const Value *Base = getUnderlyingObject(Loc.Ptr);
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if (isConstOrParam(Base->getType()->getPointerAddressSpace()))
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return ModRefInfo::NoModRef;
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return AAResultBase::getModRefInfoMask(Loc, AAQI, IgnoreLocals);
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}
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