1//===-- AMDGPUAlwaysInlinePass.cpp - Promote Allocas ----------------------===//
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/// \file
10/// This pass marks all internal functions as always_inline and creates
11/// duplicates of all other functions and marks the duplicates as always_inline.
12//
13//===----------------------------------------------------------------------===//
14
15#include "AMDGPU.h"
16#include "AMDGPUTargetMachine.h"
17#include "Utils/AMDGPUBaseInfo.h"
18#include "llvm/ADT/SmallPtrSet.h"
19#include "llvm/IR/Module.h"
20#include "llvm/Transforms/Utils/Cloning.h"
21
22using namespace llvm;
23
24namespace {
25
26static cl::opt<bool> StressCalls(
27  "amdgpu-stress-function-calls",
28  cl::Hidden,
29  cl::desc("Force all functions to be noinline"),
30  cl::init(false));
31
32class AMDGPUAlwaysInline : public ModulePass {
33  bool GlobalOpt;
34
35  void recursivelyVisitUsers(GlobalValue &GV,
36                             SmallPtrSetImpl<Function *> &FuncsToAlwaysInline);
37public:
38  static char ID;
39
40  AMDGPUAlwaysInline(bool GlobalOpt = false) :
41    ModulePass(ID), GlobalOpt(GlobalOpt) { }
42  bool runOnModule(Module &M) override;
43
44  void getAnalysisUsage(AnalysisUsage &AU) const override {
45    AU.setPreservesAll();
46 }
47};
48
49} // End anonymous namespace
50
51INITIALIZE_PASS(AMDGPUAlwaysInline, "amdgpu-always-inline",
52                "AMDGPU Inline All Functions", false, false)
53
54char AMDGPUAlwaysInline::ID = 0;
55
56void AMDGPUAlwaysInline::recursivelyVisitUsers(
57  GlobalValue &GV,
58  SmallPtrSetImpl<Function *> &FuncsToAlwaysInline) {
59  SmallVector<User *, 16> Stack;
60
61  SmallPtrSet<const Value *, 8> Visited;
62
63  for (User *U : GV.users())
64    Stack.push_back(U);
65
66  while (!Stack.empty()) {
67    User *U = Stack.pop_back_val();
68    if (!Visited.insert(U).second)
69      continue;
70
71    if (Instruction *I = dyn_cast<Instruction>(U)) {
72      Function *F = I->getParent()->getParent();
73      if (!AMDGPU::isEntryFunctionCC(F->getCallingConv())) {
74        FuncsToAlwaysInline.insert(F);
75        Stack.push_back(F);
76      }
77
78      // No need to look at further users, but we do need to inline any callers.
79      continue;
80    }
81
82    for (User *UU : U->users())
83      Stack.push_back(UU);
84  }
85}
86
87bool AMDGPUAlwaysInline::runOnModule(Module &M) {
88  std::vector<GlobalAlias*> AliasesToRemove;
89
90  SmallPtrSet<Function *, 8> FuncsToAlwaysInline;
91  SmallPtrSet<Function *, 8> FuncsToNoInline;
92
93  for (GlobalAlias &A : M.aliases()) {
94    if (Function* F = dyn_cast<Function>(A.getAliasee())) {
95      A.replaceAllUsesWith(F);
96      AliasesToRemove.push_back(&A);
97    }
98
99    // FIXME: If the aliasee isn't a function, it's some kind of constant expr
100    // cast that won't be inlined through.
101  }
102
103  if (GlobalOpt) {
104    for (GlobalAlias* A : AliasesToRemove) {
105      A->eraseFromParent();
106    }
107  }
108
109  // Always force inlining of any function that uses an LDS global address. This
110  // is something of a workaround because we don't have a way of supporting LDS
111  // objects defined in functions. LDS is always allocated by a kernel, and it
112  // is difficult to manage LDS usage if a function may be used by multiple
113  // kernels.
114  //
115  // OpenCL doesn't allow declaring LDS in non-kernels, so in practice this
116  // should only appear when IPO passes manages to move LDs defined in a kernel
117  // into a single user function.
118
119  for (GlobalVariable &GV : M.globals()) {
120    // TODO: Region address
121    unsigned AS = GV.getAddressSpace();
122    if (AS != AMDGPUAS::LOCAL_ADDRESS && AS != AMDGPUAS::REGION_ADDRESS)
123      continue;
124
125    recursivelyVisitUsers(GV, FuncsToAlwaysInline);
126  }
127
128  if (!AMDGPUTargetMachine::EnableFunctionCalls || StressCalls) {
129    auto IncompatAttr
130      = StressCalls ? Attribute::AlwaysInline : Attribute::NoInline;
131
132    for (Function &F : M) {
133      if (!F.isDeclaration() && !F.use_empty() &&
134          !F.hasFnAttribute(IncompatAttr)) {
135        if (StressCalls) {
136          if (!FuncsToAlwaysInline.count(&F))
137            FuncsToNoInline.insert(&F);
138        } else
139          FuncsToAlwaysInline.insert(&F);
140      }
141    }
142  }
143
144  for (Function *F : FuncsToAlwaysInline)
145    F->addFnAttr(Attribute::AlwaysInline);
146
147  for (Function *F : FuncsToNoInline)
148    F->addFnAttr(Attribute::NoInline);
149
150  return !FuncsToAlwaysInline.empty() || !FuncsToNoInline.empty();
151}
152
153ModulePass *llvm::createAMDGPUAlwaysInlinePass(bool GlobalOpt) {
154  return new AMDGPUAlwaysInline(GlobalOpt);
155}
156
157