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-exception 6 // 7 //===----------------------------------------------------------------------===// 8 /// \file 9 /// This is the AMGPU address space based alias analysis pass. 10 //===----------------------------------------------------------------------===// 11 12 #include "AMDGPUAliasAnalysis.h" 13 #include "AMDGPU.h" 14 #include "llvm/ADT/Triple.h" 15 #include "llvm/Analysis/AliasAnalysis.h" 16 #include "llvm/Analysis/MemoryLocation.h" 17 #include "llvm/Analysis/ValueTracking.h" 18 #include "llvm/IR/Argument.h" 19 #include "llvm/IR/Attributes.h" 20 #include "llvm/IR/CallingConv.h" 21 #include "llvm/IR/Function.h" 22 #include "llvm/IR/GlobalVariable.h" 23 #include "llvm/IR/Type.h" 24 #include "llvm/IR/Value.h" 25 #include "llvm/Pass.h" 26 #include "llvm/Support/Casting.h" 27 #include "llvm/Support/ErrorHandling.h" 28 #include <cassert> 29 30 using namespace llvm; 31 32 #define DEBUG_TYPE "amdgpu-aa" 33 34 // Register this pass... 35 char AMDGPUAAWrapperPass::ID = 0; 36 char AMDGPUExternalAAWrapper::ID = 0; 37 38 INITIALIZE_PASS(AMDGPUAAWrapperPass, "amdgpu-aa", 39 "AMDGPU Address space based Alias Analysis", false, true) 40 41 INITIALIZE_PASS(AMDGPUExternalAAWrapper, "amdgpu-aa-wrapper", 42 "AMDGPU Address space based Alias Analysis Wrapper", false, true) 43 44 ImmutablePass *llvm::createAMDGPUAAWrapperPass() { 45 return new AMDGPUAAWrapperPass(); 46 } 47 48 ImmutablePass *llvm::createAMDGPUExternalAAWrapperPass() { 49 return new AMDGPUExternalAAWrapper(); 50 } 51 52 void AMDGPUAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { 53 AU.setPreservesAll(); 54 } 55 56 // These arrays are indexed by address space value enum elements 0 ... to 7 57 static const AliasResult ASAliasRules[8][8] = { 58 /* Flat Global Region Group Constant Private Constant 32-bit Buffer Fat Ptr */ 59 /* Flat */ {MayAlias, MayAlias, NoAlias, MayAlias, MayAlias, MayAlias, MayAlias, MayAlias}, 60 /* Global */ {MayAlias, MayAlias, NoAlias , NoAlias , MayAlias, NoAlias , MayAlias, MayAlias}, 61 /* Region */ {NoAlias, NoAlias , MayAlias, NoAlias , NoAlias, NoAlias , NoAlias, NoAlias}, 62 /* Group */ {MayAlias, NoAlias , NoAlias , MayAlias, NoAlias , NoAlias , NoAlias , NoAlias}, 63 /* Constant */ {MayAlias, MayAlias, NoAlias, NoAlias , NoAlias , NoAlias , MayAlias, MayAlias}, 64 /* Private */ {MayAlias, NoAlias , NoAlias , NoAlias , NoAlias , MayAlias, NoAlias , NoAlias}, 65 /* Constant 32-bit */ {MayAlias, MayAlias, NoAlias, NoAlias , MayAlias, NoAlias , NoAlias , MayAlias}, 66 /* Buffer Fat Ptr */ {MayAlias, MayAlias, NoAlias , NoAlias , MayAlias, NoAlias , MayAlias, MayAlias} 67 }; 68 69 static AliasResult getAliasResult(unsigned AS1, unsigned AS2) { 70 static_assert(AMDGPUAS::MAX_AMDGPU_ADDRESS <= 7, "Addr space out of range"); 71 72 if (AS1 > AMDGPUAS::MAX_AMDGPU_ADDRESS || AS2 > AMDGPUAS::MAX_AMDGPU_ADDRESS) 73 return MayAlias; 74 75 return ASAliasRules[AS1][AS2]; 76 } 77 78 AliasResult AMDGPUAAResult::alias(const MemoryLocation &LocA, 79 const MemoryLocation &LocB, 80 AAQueryInfo &AAQI) { 81 unsigned asA = LocA.Ptr->getType()->getPointerAddressSpace(); 82 unsigned asB = LocB.Ptr->getType()->getPointerAddressSpace(); 83 84 AliasResult Result = getAliasResult(asA, asB); 85 if (Result == NoAlias) 86 return Result; 87 88 // Forward the query to the next alias analysis. 89 return AAResultBase::alias(LocA, LocB, AAQI); 90 } 91 92 bool AMDGPUAAResult::pointsToConstantMemory(const MemoryLocation &Loc, 93 AAQueryInfo &AAQI, bool OrLocal) { 94 unsigned AS = Loc.Ptr->getType()->getPointerAddressSpace(); 95 if (AS == AMDGPUAS::CONSTANT_ADDRESS || 96 AS == AMDGPUAS::CONSTANT_ADDRESS_32BIT) 97 return true; 98 99 const Value *Base = GetUnderlyingObject(Loc.Ptr, DL); 100 AS = Base->getType()->getPointerAddressSpace(); 101 if (AS == AMDGPUAS::CONSTANT_ADDRESS || 102 AS == AMDGPUAS::CONSTANT_ADDRESS_32BIT) 103 return true; 104 105 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) { 106 if (GV->isConstant()) 107 return true; 108 } else if (const Argument *Arg = dyn_cast<Argument>(Base)) { 109 const Function *F = Arg->getParent(); 110 111 // Only assume constant memory for arguments on kernels. 112 switch (F->getCallingConv()) { 113 default: 114 return AAResultBase::pointsToConstantMemory(Loc, AAQI, OrLocal); 115 case CallingConv::AMDGPU_LS: 116 case CallingConv::AMDGPU_HS: 117 case CallingConv::AMDGPU_ES: 118 case CallingConv::AMDGPU_GS: 119 case CallingConv::AMDGPU_VS: 120 case CallingConv::AMDGPU_PS: 121 case CallingConv::AMDGPU_CS: 122 case CallingConv::AMDGPU_KERNEL: 123 case CallingConv::SPIR_KERNEL: 124 break; 125 } 126 127 unsigned ArgNo = Arg->getArgNo(); 128 /* On an argument, ReadOnly attribute indicates that the function does 129 not write through this pointer argument, even though it may write 130 to the memory that the pointer points to. 131 On an argument, ReadNone attribute indicates that the function does 132 not dereference that pointer argument, even though it may read or write 133 the memory that the pointer points to if accessed through other pointers. 134 */ 135 if (F->hasParamAttribute(ArgNo, Attribute::NoAlias) && 136 (F->hasParamAttribute(ArgNo, Attribute::ReadNone) || 137 F->hasParamAttribute(ArgNo, Attribute::ReadOnly))) { 138 return true; 139 } 140 } 141 return AAResultBase::pointsToConstantMemory(Loc, AAQI, OrLocal); 142 } 143