LLVM  10.0.0svn
NVPTXLowerAlloca.cpp
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1 //===-- NVPTXLowerAlloca.cpp - Make alloca to use local memory =====--===//
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 //
9 // For all alloca instructions, and add a pair of cast to local address for
10 // each of them. For example,
11 //
12 // %A = alloca i32
13 // store i32 0, i32* %A ; emits st.u32
14 //
15 // will be transformed to
16 //
17 // %A = alloca i32
18 // %Local = addrspacecast i32* %A to i32 addrspace(5)*
19 // %Generic = addrspacecast i32 addrspace(5)* %A to i32*
20 // store i32 0, i32 addrspace(5)* %Generic ; emits st.local.u32
21 //
22 // And we will rely on NVPTXInferAddressSpaces to combine the last two
23 // instructions.
24 //
25 //===----------------------------------------------------------------------===//
26 
27 #include "NVPTX.h"
28 #include "NVPTXUtilities.h"
30 #include "llvm/IR/Function.h"
31 #include "llvm/IR/Instructions.h"
32 #include "llvm/IR/IntrinsicInst.h"
33 #include "llvm/IR/Module.h"
34 #include "llvm/IR/Type.h"
35 #include "llvm/Pass.h"
36 
37 using namespace llvm;
38 
39 namespace llvm {
41 }
42 
43 namespace {
44 class NVPTXLowerAlloca : public FunctionPass {
45  bool runOnFunction(Function &F) override;
46 
47 public:
48  static char ID; // Pass identification, replacement for typeid
49  NVPTXLowerAlloca() : FunctionPass(ID) {}
50  StringRef getPassName() const override {
51  return "convert address space of alloca'ed memory to local";
52  }
53 };
54 } // namespace
55 
56 char NVPTXLowerAlloca::ID = 1;
57 
58 INITIALIZE_PASS(NVPTXLowerAlloca, "nvptx-lower-alloca",
59  "Lower Alloca", false, false)
60 
61 // =============================================================================
62 // Main function for this pass.
63 // =============================================================================
64 bool NVPTXLowerAlloca::runOnFunction(Function &F) {
65  if (skipFunction(F))
66  return false;
67 
68  bool Changed = false;
69  for (auto &BB : F)
70  for (auto &I : BB) {
71  if (auto allocaInst = dyn_cast<AllocaInst>(&I)) {
72  Changed = true;
73  auto PTy = dyn_cast<PointerType>(allocaInst->getType());
74  auto ETy = PTy->getElementType();
75  auto LocalAddrTy = PointerType::get(ETy, ADDRESS_SPACE_LOCAL);
76  auto NewASCToLocal = new AddrSpaceCastInst(allocaInst, LocalAddrTy, "");
77  auto GenericAddrTy = PointerType::get(ETy, ADDRESS_SPACE_GENERIC);
78  auto NewASCToGeneric =
79  new AddrSpaceCastInst(NewASCToLocal, GenericAddrTy, "");
80  NewASCToLocal->insertAfter(allocaInst);
81  NewASCToGeneric->insertAfter(NewASCToLocal);
82  for (Value::use_iterator UI = allocaInst->use_begin(),
83  UE = allocaInst->use_end();
84  UI != UE;) {
85  // Check Load, Store, GEP, and BitCast Uses on alloca and make them
86  // use the converted generic address, in order to expose non-generic
87  // addrspacecast to NVPTXInferAddressSpaces. For other types
88  // of instructions this is unnecessary and may introduce redundant
89  // address cast.
90  const auto &AllocaUse = *UI++;
91  auto LI = dyn_cast<LoadInst>(AllocaUse.getUser());
92  if (LI && LI->getPointerOperand() == allocaInst &&
93  !LI->isVolatile()) {
94  LI->setOperand(LI->getPointerOperandIndex(), NewASCToGeneric);
95  continue;
96  }
97  auto SI = dyn_cast<StoreInst>(AllocaUse.getUser());
98  if (SI && SI->getPointerOperand() == allocaInst &&
99  !SI->isVolatile()) {
100  SI->setOperand(SI->getPointerOperandIndex(), NewASCToGeneric);
101  continue;
102  }
103  auto GI = dyn_cast<GetElementPtrInst>(AllocaUse.getUser());
104  if (GI && GI->getPointerOperand() == allocaInst) {
105  GI->setOperand(GI->getPointerOperandIndex(), NewASCToGeneric);
106  continue;
107  }
108  auto BI = dyn_cast<BitCastInst>(AllocaUse.getUser());
109  if (BI && BI->getOperand(0) == allocaInst) {
110  BI->setOperand(0, NewASCToGeneric);
111  continue;
112  }
113  }
114  }
115  }
116  return Changed;
117 }
118 
120  return new NVPTXLowerAlloca();
121 }
This class represents lattice values for constants.
Definition: AllocatorList.h:23
static PointerType * get(Type *ElementType, unsigned AddressSpace)
This constructs a pointer to an object of the specified type in a numbered address space...
Definition: Type.cpp:637
F(f)
An instruction for reading from memory.
Definition: Instructions.h:169
FunctionPass * createNVPTXLowerAllocaPass()
This class represents a conversion between pointers from one address space to another.
INITIALIZE_PASS(NVPTXLowerAlloca, "nvptx-lower-alloca", "Lower Alloca", false, false) bool NVPTXLowerAlloca
This class represents a no-op cast from one type to another.
An instruction for storing to memory.
Definition: Instructions.h:325
Class to represent pointers.
Definition: DerivedTypes.h:579
use_iterator_impl< Use > use_iterator
Definition: Value.h:352
an instruction for type-safe pointer arithmetic to access elements of arrays and structs ...
Definition: Instructions.h:881
static bool runOnFunction(Function &F, bool PostInlining)
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:284
void initializeNVPTXLowerAllocaPass(PassRegistry &)
Module.h This file contains the declarations for the Module class.
void setOperand(unsigned i, Value *Val)
Definition: User.h:174
#define I(x, y, z)
Definition: MD5.cpp:58
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:332
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
PassRegistry - This class manages the registration and intitialization of the pass subsystem as appli...
Definition: PassRegistry.h:38
Type * getElementType() const
Definition: DerivedTypes.h:598