llvm/lib/Target/NVPTX/NVPTXAliasAnalysis.cpp

   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
  34 ImmutablePass *llvm::createNVPTXAAWrapperPass() {
  35   return new NVPTXAAWrapperPass();
  36 }
  37
  38 ImmutablePass *llvm::createNVPTXExternalAAWrapperPass() {
  39   return new NVPTXExternalAAWrapper();
  40 }
  41
  42 NVPTXAAWrapperPass::NVPTXAAWrapperPass() : ImmutablePass(ID) {
  43   initializeNVPTXAAWrapperPassPass(*PassRegistry::getPassRegistry());
  44 }
  45
  46 void NVPTXAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
  47   AU.setPreservesAll();
  48 }
  49
  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
  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.
  82 static bool isConstOrParam(unsigned AS) {
  83   return AS == AddressSpace::ADDRESS_SPACE_CONST ||
  84          AS == AddressSpace::ADDRESS_SPACE_PARAM;
  85 }
  86
  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 }