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 Constant Group Region 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 assert(AS.MAX_COMMON_ADDRESS <= 5); 73 if (AS.FLAT_ADDRESS == 0) { 74 assert(AS.GLOBAL_ADDRESS == 1 && 75 AS.REGION_ADDRESS == 4 && 76 AS.LOCAL_ADDRESS == 3 && 77 AS.CONSTANT_ADDRESS == 2 && 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 return true; 120 } 121 122 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) { 123 if (GV->isConstant()) 124 return true; 125 } else if (const Argument *Arg = dyn_cast<Argument>(Base)) { 126 const Function *F = Arg->getParent(); 127 128 // Only assume constant memory for arguments on kernels. 129 switch (F->getCallingConv()) { 130 default: 131 return AAResultBase::pointsToConstantMemory(Loc, OrLocal); 132 case CallingConv::AMDGPU_VS: 133 case CallingConv::AMDGPU_GS: 134 case CallingConv::AMDGPU_PS: 135 case CallingConv::AMDGPU_CS: 136 case CallingConv::AMDGPU_KERNEL: 137 case CallingConv::SPIR_KERNEL: 138 break; 139 } 140 141 unsigned ArgNo = Arg->getArgNo(); 142 /* On an argument, ReadOnly attribute indicates that the function does 143 not write through this pointer argument, even though it may write 144 to the memory that the pointer points to. 145 On an argument, ReadNone attribute indicates that the function does 146 not dereference that pointer argument, even though it may read or write 147 the memory that the pointer points to if accessed through other pointers. 148 */ 149 if (F->hasParamAttribute(ArgNo, Attribute::NoAlias) && 150 (F->hasParamAttribute(ArgNo, Attribute::ReadNone) || 151 F->hasParamAttribute(ArgNo, Attribute::ReadOnly))) { 152 return true; 153 } 154 } 155 return AAResultBase::pointsToConstantMemory(Loc, OrLocal); 156 } 157