117 lines · cpp
1//===- AMDGPUAliasAnalysis ------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8/// \file9/// This is the AMGPU address space based alias analysis pass.10//===----------------------------------------------------------------------===//11 12#include "AMDGPUAliasAnalysis.h"13#include "AMDGPU.h"14#include "llvm/Analysis/ValueTracking.h"15#include "llvm/IR/Instructions.h"16 17using namespace llvm;18 19#define DEBUG_TYPE "amdgpu-aa"20 21AnalysisKey AMDGPUAA::Key;22 23// Register this pass...24char AMDGPUAAWrapperPass::ID = 0;25char AMDGPUExternalAAWrapper::ID = 0;26 27INITIALIZE_PASS(AMDGPUAAWrapperPass, "amdgpu-aa",28 "AMDGPU Address space based Alias Analysis", false, true)29 30INITIALIZE_PASS(AMDGPUExternalAAWrapper, "amdgpu-aa-wrapper",31 "AMDGPU Address space based Alias Analysis Wrapper", false, true)32 33ImmutablePass *llvm::createAMDGPUAAWrapperPass() {34 return new AMDGPUAAWrapperPass();35}36 37ImmutablePass *llvm::createAMDGPUExternalAAWrapperPass() {38 return new AMDGPUExternalAAWrapper();39}40 41AMDGPUAAWrapperPass::AMDGPUAAWrapperPass() : ImmutablePass(ID) {}42 43void AMDGPUAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {44 AU.setPreservesAll();45}46 47AliasResult AMDGPUAAResult::alias(const MemoryLocation &LocA,48 const MemoryLocation &LocB, AAQueryInfo &AAQI,49 const Instruction *) {50 unsigned asA = LocA.Ptr->getType()->getPointerAddressSpace();51 unsigned asB = LocB.Ptr->getType()->getPointerAddressSpace();52 53 if (!AMDGPU::addrspacesMayAlias(asA, asB))54 return AliasResult::NoAlias;55 56 // In general, FLAT (generic) pointers could be aliased to LOCAL or PRIVATE57 // pointers. However, as LOCAL or PRIVATE pointers point to local objects, in58 // certain cases, it's still viable to check whether a FLAT pointer won't59 // alias to a LOCAL or PRIVATE pointer.60 MemoryLocation A = LocA;61 MemoryLocation B = LocB;62 // Canonicalize the location order to simplify the following alias check.63 if (asA != AMDGPUAS::FLAT_ADDRESS) {64 std::swap(asA, asB);65 std::swap(A, B);66 }67 if (asA == AMDGPUAS::FLAT_ADDRESS &&68 (asB == AMDGPUAS::LOCAL_ADDRESS || asB == AMDGPUAS::PRIVATE_ADDRESS)) {69 const auto *ObjA =70 getUnderlyingObject(A.Ptr->stripPointerCastsForAliasAnalysis());71 if (const LoadInst *LI = dyn_cast<LoadInst>(ObjA)) {72 // If a generic pointer is loaded from the constant address space, it73 // could only be a GLOBAL or CONSTANT one as that address space is solely74 // prepared on the host side, where only GLOBAL or CONSTANT variables are75 // visible. Note that this even holds for regular functions.76 if (LI->getPointerAddressSpace() == AMDGPUAS::CONSTANT_ADDRESS)77 return AliasResult::NoAlias;78 } else if (const Argument *Arg = dyn_cast<Argument>(ObjA)) {79 const Function *F = Arg->getParent();80 switch (F->getCallingConv()) {81 case CallingConv::AMDGPU_KERNEL: {82 // In the kernel function, kernel arguments won't alias to (local)83 // variables in shared or private address space.84 const auto *ObjB =85 getUnderlyingObject(B.Ptr->stripPointerCastsForAliasAnalysis());86 return ObjA != ObjB && isIdentifiedObject(ObjB) ? AliasResult::NoAlias87 : AliasResult::MayAlias;88 }89 default:90 // TODO: In the regular function, if that local variable in the91 // location B is not captured, that argument pointer won't alias to it92 // as well.93 break;94 }95 }96 }97 98 return AliasResult::MayAlias;99}100 101ModRefInfo AMDGPUAAResult::getModRefInfoMask(const MemoryLocation &Loc,102 AAQueryInfo &AAQI,103 bool IgnoreLocals) {104 unsigned AS = Loc.Ptr->getType()->getPointerAddressSpace();105 if (AS == AMDGPUAS::CONSTANT_ADDRESS ||106 AS == AMDGPUAS::CONSTANT_ADDRESS_32BIT)107 return ModRefInfo::NoModRef;108 109 const Value *Base = getUnderlyingObject(Loc.Ptr);110 AS = Base->getType()->getPointerAddressSpace();111 if (AS == AMDGPUAS::CONSTANT_ADDRESS ||112 AS == AMDGPUAS::CONSTANT_ADDRESS_32BIT)113 return ModRefInfo::NoModRef;114 115 return ModRefInfo::ModRef;116}117