1 //===- AMDGPUAliasAnalysis ------------------------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 /// \file 10 /// This is the AMGPU address space based alias analysis pass. 11 //===----------------------------------------------------------------------===// 12 13 #include "AMDGPUAliasAnalysis.h" 14 #include "AMDGPU.h" 15 #include "llvm/ADT/Triple.h" 16 #include "llvm/Analysis/AliasAnalysis.h" 17 #include "llvm/Analysis/MemoryLocation.h" 18 #include "llvm/Analysis/ValueTracking.h" 19 #include "llvm/IR/Argument.h" 20 #include "llvm/IR/Attributes.h" 21 #include "llvm/IR/CallingConv.h" 22 #include "llvm/IR/Function.h" 23 #include "llvm/IR/GlobalVariable.h" 24 #include "llvm/IR/Type.h" 25 #include "llvm/IR/Value.h" 26 #include "llvm/Pass.h" 27 #include "llvm/Support/Casting.h" 28 #include "llvm/Support/ErrorHandling.h" 29 #include <cassert> 30 31 using namespace llvm; 32 33 #define DEBUG_TYPE "amdgpu-aa" 34 35 // Register this pass... 36 char AMDGPUAAWrapperPass::ID = 0; 37 38 INITIALIZE_PASS(AMDGPUAAWrapperPass, "amdgpu-aa", 39 "AMDGPU Address space based Alias Analysis", false, true) 40 41 ImmutablePass *llvm::createAMDGPUAAWrapperPass() { 42 return new AMDGPUAAWrapperPass(); 43 } 44 45 void AMDGPUAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const { 46 AU.setPreservesAll(); 47 } 48 49 // Must match the table in getAliasResult. 50 AMDGPUAAResult::ASAliasRulesTy::ASAliasRulesTy(AMDGPUAS AS_, Triple::ArchType Arch_) 51 : Arch(Arch_), AS(AS_) { 52 // These arrarys are indexed by address space value 53 // enum elements 0 ... to 5 54 static const AliasResult ASAliasRulesPrivIsZero[6][6] = { 55 /* Private Global Constant Group Flat Region*/ 56 /* Private */ {MayAlias, NoAlias , NoAlias , NoAlias , MayAlias, NoAlias}, 57 /* Global */ {NoAlias , MayAlias, NoAlias , NoAlias , MayAlias, NoAlias}, 58 /* Constant */ {NoAlias , NoAlias , MayAlias, NoAlias , MayAlias, NoAlias}, 59 /* Group */ {NoAlias , NoAlias , NoAlias , MayAlias, MayAlias, NoAlias}, 60 /* Flat */ {MayAlias, MayAlias, MayAlias, MayAlias, MayAlias, MayAlias}, 61 /* Region */ {NoAlias , NoAlias , NoAlias , NoAlias , MayAlias, MayAlias} 62 }; 63 static const AliasResult ASAliasRulesGenIsZero[6][6] = { 64 /* Flat Global Region Group Constant Private */ 65 /* Flat */ {MayAlias, MayAlias, MayAlias, MayAlias, MayAlias, MayAlias}, 66 /* Global */ {MayAlias, MayAlias, NoAlias , NoAlias , NoAlias , NoAlias}, 67 /* Constant */ {MayAlias, NoAlias , MayAlias, NoAlias , NoAlias, NoAlias}, 68 /* Group */ {MayAlias, NoAlias , NoAlias , MayAlias, NoAlias , NoAlias}, 69 /* Region */ {MayAlias, NoAlias , NoAlias , NoAlias, MayAlias, NoAlias}, 70 /* Private */ {MayAlias, NoAlias , NoAlias , NoAlias , NoAlias , MayAlias} 71 }; 72 static_assert(AS.MAX_COMMON_ADDRESS <= 6, "Addr space out of range"); 73 if (AS.FLAT_ADDRESS == 0) { 74 assert(AS.GLOBAL_ADDRESS == 1 && 75 AS.REGION_ADDRESS == 2 && 76 AS.LOCAL_ADDRESS == 3 && 77 AS.CONSTANT_ADDRESS == 4 && 78 AS.PRIVATE_ADDRESS == 5); 79 ASAliasRules = &ASAliasRulesGenIsZero; 80 } else { 81 assert(AS.PRIVATE_ADDRESS == 0 && 82 AS.GLOBAL_ADDRESS == 1 && 83 AS.CONSTANT_ADDRESS == 2 && 84 AS.LOCAL_ADDRESS == 3 && 85 AS.FLAT_ADDRESS == 4 && 86 AS.REGION_ADDRESS == 5); 87 ASAliasRules = &ASAliasRulesPrivIsZero; 88 } 89 } 90 91 AliasResult AMDGPUAAResult::ASAliasRulesTy::getAliasResult(unsigned AS1, 92 unsigned AS2) const { 93 if (AS1 > AS.MAX_COMMON_ADDRESS || AS2 > AS.MAX_COMMON_ADDRESS) { 94 if (Arch == Triple::amdgcn) 95 report_fatal_error("Pointer address space out of range"); 96 return AS1 == AS2 ? MayAlias : NoAlias; 97 } 98 99 return (*ASAliasRules)[AS1][AS2]; 100 } 101 102 AliasResult AMDGPUAAResult::alias(const MemoryLocation &LocA, 103 const MemoryLocation &LocB) { 104 unsigned asA = LocA.Ptr->getType()->getPointerAddressSpace(); 105 unsigned asB = LocB.Ptr->getType()->getPointerAddressSpace(); 106 107 AliasResult Result = ASAliasRules.getAliasResult(asA, asB); 108 if (Result == NoAlias) return Result; 109 110 // Forward the query to the next alias analysis. 111 return AAResultBase::alias(LocA, LocB); 112 } 113 114 bool AMDGPUAAResult::pointsToConstantMemory(const MemoryLocation &Loc, 115 bool OrLocal) { 116 const Value *Base = GetUnderlyingObject(Loc.Ptr, DL); 117 118 if (Base->getType()->getPointerAddressSpace() == AS.CONSTANT_ADDRESS || 119 Base->getType()->getPointerAddressSpace() == AS.CONSTANT_ADDRESS_32BIT) { 120 return true; 121 } 122 123 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) { 124 if (GV->isConstant()) 125 return true; 126 } else if (const Argument *Arg = dyn_cast<Argument>(Base)) { 127 const Function *F = Arg->getParent(); 128 129 // Only assume constant memory for arguments on kernels. 130 switch (F->getCallingConv()) { 131 default: 132 return AAResultBase::pointsToConstantMemory(Loc, OrLocal); 133 case CallingConv::AMDGPU_LS: 134 case CallingConv::AMDGPU_HS: 135 case CallingConv::AMDGPU_ES: 136 case CallingConv::AMDGPU_GS: 137 case CallingConv::AMDGPU_VS: 138 case CallingConv::AMDGPU_PS: 139 case CallingConv::AMDGPU_CS: 140 case CallingConv::AMDGPU_KERNEL: 141 case CallingConv::SPIR_KERNEL: 142 break; 143 } 144 145 unsigned ArgNo = Arg->getArgNo(); 146 /* On an argument, ReadOnly attribute indicates that the function does 147 not write through this pointer argument, even though it may write 148 to the memory that the pointer points to. 149 On an argument, ReadNone attribute indicates that the function does 150 not dereference that pointer argument, even though it may read or write 151 the memory that the pointer points to if accessed through other pointers. 152 */ 153 if (F->hasParamAttribute(ArgNo, Attribute::NoAlias) && 154 (F->hasParamAttribute(ArgNo, Attribute::ReadNone) || 155 F->hasParamAttribute(ArgNo, Attribute::ReadOnly))) { 156 return true; 157 } 158 } 159 return AAResultBase::pointsToConstantMemory(Loc, OrLocal); 160 } 161