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
createNVPTXAAWrapperPass()34 ImmutablePass *llvm::createNVPTXAAWrapperPass() {
35 return new NVPTXAAWrapperPass();
36 }
37
createNVPTXExternalAAWrapperPass()38 ImmutablePass *llvm::createNVPTXExternalAAWrapperPass() {
39 return new NVPTXExternalAAWrapper();
40 }
41
NVPTXAAWrapperPass()42 NVPTXAAWrapperPass::NVPTXAAWrapperPass() : ImmutablePass(ID) {
43 initializeNVPTXAAWrapperPassPass(*PassRegistry::getPassRegistry());
44 }
45
getAnalysisUsage(AnalysisUsage & AU) const46 void NVPTXAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
47 AU.setPreservesAll();
48 }
49
getAliasResult(unsigned AS1,unsigned AS2)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
alias(const MemoryLocation & Loc1,const MemoryLocation & Loc2,AAQueryInfo & AAQI,const Instruction *)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.
isConstOrParam(unsigned AS)82 static bool isConstOrParam(unsigned AS) {
83 return AS == AddressSpace::ADDRESS_SPACE_CONST ||
84 AS == AddressSpace::ADDRESS_SPACE_PARAM;
85 }
86
getModRefInfoMask(const MemoryLocation & Loc,AAQueryInfo & AAQI,bool IgnoreLocals)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