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
createAMDGPUAAWrapperPass()41 ImmutablePass *llvm::createAMDGPUAAWrapperPass() {
42 return new AMDGPUAAWrapperPass();
43 }
44
getAnalysisUsage(AnalysisUsage & AU) const45 void AMDGPUAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
46 AU.setPreservesAll();
47 }
48
49 // Must match the table in getAliasResult.
ASAliasRulesTy(AMDGPUAS AS_,Triple::ArchType Arch_)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 6
54 static const AliasResult ASAliasRulesPrivIsZero[7][7] = {
55 /* Private Global Constant Group Flat Region Constant 32-bit */
56 /* Private */ {MayAlias, NoAlias , NoAlias , NoAlias , MayAlias, NoAlias , NoAlias},
57 /* Global */ {NoAlias , MayAlias, MayAlias, NoAlias , MayAlias, NoAlias , MayAlias},
58 /* Constant */ {NoAlias , MayAlias, MayAlias, NoAlias , MayAlias, NoAlias , MayAlias},
59 /* Group */ {NoAlias , NoAlias , NoAlias , MayAlias, MayAlias, NoAlias , NoAlias},
60 /* Flat */ {MayAlias, MayAlias, MayAlias, MayAlias, MayAlias, MayAlias, MayAlias},
61 /* Region */ {NoAlias , NoAlias , NoAlias , NoAlias , MayAlias, MayAlias, NoAlias},
62 /* Constant 32-bit */ {NoAlias , MayAlias, MayAlias, NoAlias , MayAlias, NoAlias , MayAlias}
63 };
64 static const AliasResult ASAliasRulesGenIsZero[7][7] = {
65 /* Flat Global Region Group Constant Private Constant 32-bit */
66 /* Flat */ {MayAlias, MayAlias, MayAlias, MayAlias, MayAlias, MayAlias, MayAlias},
67 /* Global */ {MayAlias, MayAlias, NoAlias , NoAlias , MayAlias, NoAlias , MayAlias},
68 /* Region */ {MayAlias, NoAlias , NoAlias , NoAlias, MayAlias, NoAlias , MayAlias},
69 /* Group */ {MayAlias, NoAlias , NoAlias , MayAlias, NoAlias , NoAlias , NoAlias},
70 /* Constant */ {MayAlias, MayAlias, MayAlias, NoAlias , NoAlias, NoAlias , MayAlias},
71 /* Private */ {MayAlias, NoAlias , NoAlias , NoAlias , NoAlias , MayAlias, NoAlias},
72 /* Constant 32-bit */ {MayAlias, MayAlias, MayAlias, NoAlias , MayAlias, NoAlias , NoAlias}
73 };
74 static_assert(AMDGPUAS::MAX_AMDGPU_ADDRESS <= 6, "Addr space out of range");
75 if (AS.FLAT_ADDRESS == 0) {
76 assert(AS.GLOBAL_ADDRESS == 1 &&
77 AS.REGION_ADDRESS == 2 &&
78 AS.LOCAL_ADDRESS == 3 &&
79 AS.CONSTANT_ADDRESS == 4 &&
80 AS.PRIVATE_ADDRESS == 5 &&
81 AS.CONSTANT_ADDRESS_32BIT == 6);
82 ASAliasRules = &ASAliasRulesGenIsZero;
83 } else {
84 assert(AS.PRIVATE_ADDRESS == 0 &&
85 AS.GLOBAL_ADDRESS == 1 &&
86 AS.CONSTANT_ADDRESS == 2 &&
87 AS.LOCAL_ADDRESS == 3 &&
88 AS.FLAT_ADDRESS == 4 &&
89 AS.REGION_ADDRESS == 5 &&
90 AS.CONSTANT_ADDRESS_32BIT == 6);
91 ASAliasRules = &ASAliasRulesPrivIsZero;
92 }
93 }
94
getAliasResult(unsigned AS1,unsigned AS2) const95 AliasResult AMDGPUAAResult::ASAliasRulesTy::getAliasResult(unsigned AS1,
96 unsigned AS2) const {
97 if (AS1 > AS.MAX_AMDGPU_ADDRESS || AS2 > AS.MAX_AMDGPU_ADDRESS) {
98 if (Arch == Triple::amdgcn)
99 report_fatal_error("Pointer address space out of range");
100 return AS1 == AS2 ? MayAlias : NoAlias;
101 }
102
103 return (*ASAliasRules)[AS1][AS2];
104 }
105
alias(const MemoryLocation & LocA,const MemoryLocation & LocB)106 AliasResult AMDGPUAAResult::alias(const MemoryLocation &LocA,
107 const MemoryLocation &LocB) {
108 unsigned asA = LocA.Ptr->getType()->getPointerAddressSpace();
109 unsigned asB = LocB.Ptr->getType()->getPointerAddressSpace();
110
111 AliasResult Result = ASAliasRules.getAliasResult(asA, asB);
112 if (Result == NoAlias) return Result;
113
114 // Forward the query to the next alias analysis.
115 return AAResultBase::alias(LocA, LocB);
116 }
117
pointsToConstantMemory(const MemoryLocation & Loc,bool OrLocal)118 bool AMDGPUAAResult::pointsToConstantMemory(const MemoryLocation &Loc,
119 bool OrLocal) {
120 const Value *Base = GetUnderlyingObject(Loc.Ptr, DL);
121
122 if (Base->getType()->getPointerAddressSpace() == AS.CONSTANT_ADDRESS ||
123 Base->getType()->getPointerAddressSpace() == AS.CONSTANT_ADDRESS_32BIT) {
124 return true;
125 }
126
127 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) {
128 if (GV->isConstant())
129 return true;
130 } else if (const Argument *Arg = dyn_cast<Argument>(Base)) {
131 const Function *F = Arg->getParent();
132
133 // Only assume constant memory for arguments on kernels.
134 switch (F->getCallingConv()) {
135 default:
136 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
137 case CallingConv::AMDGPU_LS:
138 case CallingConv::AMDGPU_HS:
139 case CallingConv::AMDGPU_ES:
140 case CallingConv::AMDGPU_GS:
141 case CallingConv::AMDGPU_VS:
142 case CallingConv::AMDGPU_PS:
143 case CallingConv::AMDGPU_CS:
144 case CallingConv::AMDGPU_KERNEL:
145 case CallingConv::SPIR_KERNEL:
146 break;
147 }
148
149 unsigned ArgNo = Arg->getArgNo();
150 /* On an argument, ReadOnly attribute indicates that the function does
151 not write through this pointer argument, even though it may write
152 to the memory that the pointer points to.
153 On an argument, ReadNone attribute indicates that the function does
154 not dereference that pointer argument, even though it may read or write
155 the memory that the pointer points to if accessed through other pointers.
156 */
157 if (F->hasParamAttribute(ArgNo, Attribute::NoAlias) &&
158 (F->hasParamAttribute(ArgNo, Attribute::ReadNone) ||
159 F->hasParamAttribute(ArgNo, Attribute::ReadOnly))) {
160 return true;
161 }
162 }
163 return AAResultBase::pointsToConstantMemory(Loc, OrLocal);
164 }
165