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
19using namespace llvm;
20
21#define DEBUG_TYPE "NVPTX-aa"
22
23AnalysisKey NVPTXAA::Key;
24
25char NVPTXAAWrapperPass::ID = 0;
26char NVPTXExternalAAWrapper::ID = 0;
27
28INITIALIZE_PASS(NVPTXAAWrapperPass, "nvptx-aa",
29 "NVPTX Address space based Alias Analysis", false, true)
30
31INITIALIZE_PASS(NVPTXExternalAAWrapper, "nvptx-aa-wrapper",
32 "NVPTX Address space based Alias Analysis Wrapper", false, true)
33
34ImmutablePass *llvm::createNVPTXAAWrapperPass() {
35 return new NVPTXAAWrapperPass();
36}
37
38ImmutablePass *llvm::createNVPTXExternalAAWrapperPass() {
39 return new NVPTXExternalAAWrapper();
40}
41
42NVPTXAAWrapperPass::NVPTXAAWrapperPass() : ImmutablePass(ID) {
43 initializeNVPTXAAWrapperPassPass(Registry&: *PassRegistry::getPassRegistry());
44}
45
46void NVPTXAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
47 AU.setPreservesAll();
48}
49
50static 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
70AliasResult 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.
82static bool isConstOrParam(unsigned AS) {
83 return AS == AddressSpace::ADDRESS_SPACE_CONST ||
84 AS == AddressSpace::ADDRESS_SPACE_PARAM;
85}
86
87ModRefInfo NVPTXAAResult::getModRefInfoMask(const MemoryLocation &Loc,
88 AAQueryInfo &AAQI,
89 bool IgnoreLocals) {
90 if (isConstOrParam(AS: Loc.Ptr->getType()->getPointerAddressSpace()))
91 return ModRefInfo::NoModRef;
92
93 const Value *Base = getUnderlyingObject(V: Loc.Ptr);
94 if (isConstOrParam(AS: Base->getType()->getPointerAddressSpace()))
95 return ModRefInfo::NoModRef;
96
97 return ModRefInfo::ModRef;
98}
99