1 //===--------------------- NVPTXAliasAnalysis.cpp--------------------------===// 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-exception 6 // 7 //===----------------------------------------------------------------------===// 8 /// \file 9 /// This is the NVPTX address space based alias analysis pass. 10 //===----------------------------------------------------------------------===// 11 12 #include "NVPTXAliasAnalysis.h" 13 #include "MCTargetDesc/NVPTXBaseInfo.h" 14 #include "NVPTX.h" 15 #include "llvm/Analysis/ValueTracking.h" 16 #include "llvm/IR/CallingConv.h" 17 #include "llvm/IR/Instructions.h" 18 19 using namespace llvm; 20 21 #define DEBUG_TYPE "NVPTX-aa" 22 23 AnalysisKey NVPTXAA::Key; 24 25 char NVPTXAAWrapperPass::ID = 0; 26 char NVPTXExternalAAWrapper::ID = 0; 27 28 INITIALIZE_PASS(NVPTXAAWrapperPass, "nvptx-aa", 29 "NVPTX Address space based Alias Analysis", false, true) 30 31 INITIALIZE_PASS(NVPTXExternalAAWrapper, "nvptx-aa-wrapper", 32 "NVPTX Address space based Alias Analysis Wrapper", false, true) 33 34 ImmutablePass *llvm::createNVPTXAAWrapperPass() { 35 return new NVPTXAAWrapperPass(); 36 } 37 38 ImmutablePass *llvm::createNVPTXExternalAAWrapperPass() { 39 return new NVPTXExternalAAWrapper(); 40 } 41 42 NVPTXAAWrapperPass::NVPTXAAWrapperPass() : ImmutablePass(ID) { 43 initializeNVPTXAAWrapperPassPass(*PassRegistry::getPassRegistry()); 44 } 45 46 void NVPTXAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { 47 AU.setPreservesAll(); 48 } 49 50 static AliasResult::Kind getAliasResult(unsigned AS1, unsigned AS2) { 51 if ((AS1 == ADDRESS_SPACE_GENERIC) || (AS2 == ADDRESS_SPACE_GENERIC)) 52 return AliasResult::MayAlias; 53 54 // PTX s6.4.1.1. Generic Addressing: 55 // A generic address maps to global memory unless it falls within 56 // the window for const, local, or shared memory. The Kernel 57 // Function Parameters (.param) window is contained within the 58 // .global window. 59 // 60 // Therefore a global pointer may alias with a param pointer on some 61 // GPUs via addrspacecast(param->generic->global) when cvta.param 62 // instruction is used (PTX 7.7+ and SM_70+). 63 // 64 // TODO: cvta.param is not yet supported. We need to change aliasing 65 // rules once it is added. 66 67 return (AS1 == AS2 ? AliasResult::MayAlias : AliasResult::NoAlias); 68 } 69 70 AliasResult NVPTXAAResult::alias(const MemoryLocation &Loc1, 71 const MemoryLocation &Loc2, AAQueryInfo &AAQI, 72 const Instruction *) { 73 unsigned AS1 = Loc1.Ptr->getType()->getPointerAddressSpace(); 74 unsigned AS2 = Loc2.Ptr->getType()->getPointerAddressSpace(); 75 76 return getAliasResult(AS1, AS2); 77 } 78 79 // TODO: .param address space may be writable in presence of cvta.param, but 80 // this instruction is currently not supported. NVPTXLowerArgs also does not 81 // allow any writes to .param pointers. 82 static bool isConstOrParam(unsigned AS) { 83 return AS == AddressSpace::ADDRESS_SPACE_CONST || 84 AS == AddressSpace::ADDRESS_SPACE_PARAM; 85 } 86 87 ModRefInfo NVPTXAAResult::getModRefInfoMask(const MemoryLocation &Loc, 88 AAQueryInfo &AAQI, 89 bool IgnoreLocals) { 90 if (isConstOrParam(Loc.Ptr->getType()->getPointerAddressSpace())) 91 return ModRefInfo::NoModRef; 92 93 const Value *Base = getUnderlyingObject(Loc.Ptr); 94 if (isConstOrParam(Base->getType()->getPointerAddressSpace())) 95 return ModRefInfo::NoModRef; 96 97 return ModRefInfo::ModRef; 98 } 99