1 //===-- PPCLowerMASSVEntries.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 //
9 // This file implements lowering of MASSV (SIMD) entries for specific PowerPC
10 // subtargets.
11 // Following is an example of a conversion specific to Power9 subtarget:
12 // __sind2_massv ---> __sind2_P9
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "PPC.h"
17 #include "PPCSubtarget.h"
18 #include "PPCTargetMachine.h"
19 #include "llvm/Analysis/TargetTransformInfo.h"
20 #include "llvm/CodeGen/TargetPassConfig.h"
21 #include "llvm/IR/Instructions.h"
22 #include "llvm/IR/Module.h"
23 
24 #define DEBUG_TYPE "ppc-lower-massv-entries"
25 
26 using namespace llvm;
27 
28 namespace {
29 
30 // Length of the suffix "massv", which is specific to IBM MASSV library entries.
31 const unsigned MASSVSuffixLength = 5;
32 
33 static StringRef MASSVFuncs[] = {
34 #define TLI_DEFINE_MASSV_VECFUNCS_NAMES
35 #include "llvm/Analysis/VecFuncs.def"
36 };
37 
38 class PPCLowerMASSVEntries : public ModulePass {
39 public:
40   static char ID;
41 
42   PPCLowerMASSVEntries() : ModulePass(ID) {}
43 
44   bool runOnModule(Module &M) override;
45 
46   StringRef getPassName() const override { return "PPC Lower MASS Entries"; }
47 
48   void getAnalysisUsage(AnalysisUsage &AU) const override {
49     AU.addRequired<TargetTransformInfoWrapperPass>();
50   }
51 
52 private:
53   static bool isMASSVFunc(StringRef Name);
54   static StringRef getCPUSuffix(const PPCSubtarget *Subtarget);
55   static std::string createMASSVFuncName(Function &Func,
56                                          const PPCSubtarget *Subtarget);
57   bool lowerMASSVCall(CallInst *CI, Function &Func, Module &M,
58                       const PPCSubtarget *Subtarget);
59 };
60 
61 } // namespace
62 
63 /// Checks if the specified function name represents an entry in the MASSV
64 /// library.
65 bool PPCLowerMASSVEntries::isMASSVFunc(StringRef Name) {
66   auto Iter = std::find(std::begin(MASSVFuncs), std::end(MASSVFuncs), Name);
67   return Iter != std::end(MASSVFuncs);
68 }
69 
70 // FIXME:
71 /// Returns a string corresponding to the specified PowerPC subtarget. e.g.:
72 /// "P8" for Power8, "P9" for Power9. The string is used as a suffix while
73 /// generating subtarget-specific MASSV library functions. Current support
74 /// includes  Power8 and Power9 subtargets.
75 StringRef PPCLowerMASSVEntries::getCPUSuffix(const PPCSubtarget *Subtarget) {
76   // Assume Power8 when Subtarget is unavailable.
77   if (!Subtarget)
78     return "P8";
79   if (Subtarget->hasP9Vector())
80     return "P9";
81   if (Subtarget->hasP8Vector())
82     return "P8";
83 
84   report_fatal_error("Unsupported Subtarget: MASSV is supported only on "
85                      "Power8 and Power9 subtargets.");
86 }
87 
88 /// Creates PowerPC subtarget-specific name corresponding to the specified
89 /// generic MASSV function, and the PowerPC subtarget.
90 std::string
91 PPCLowerMASSVEntries::createMASSVFuncName(Function &Func,
92                                           const PPCSubtarget *Subtarget) {
93   StringRef Suffix = getCPUSuffix(Subtarget);
94   auto GenericName = Func.getName().drop_back(MASSVSuffixLength).str();
95   std::string MASSVEntryName = GenericName + Suffix.str();
96   return MASSVEntryName;
97 }
98 
99 /// Lowers generic MASSV entries to PowerPC subtarget-specific MASSV entries.
100 /// e.g.: __sind2_massv --> __sind2_P9 for a Power9 subtarget.
101 /// Both function prototypes and their callsites are updated during lowering.
102 bool PPCLowerMASSVEntries::lowerMASSVCall(CallInst *CI, Function &Func,
103                                           Module &M,
104                                           const PPCSubtarget *Subtarget) {
105   if (CI->use_empty())
106     return false;
107 
108   std::string MASSVEntryName = createMASSVFuncName(Func, Subtarget);
109   FunctionCallee FCache = M.getOrInsertFunction(
110       MASSVEntryName, Func.getFunctionType(), Func.getAttributes());
111 
112   CallSite CS(CI);
113   CI->setCalledFunction(FCache);
114 
115   return true;
116 }
117 
118 bool PPCLowerMASSVEntries::runOnModule(Module &M) {
119   bool Changed = false;
120 
121   auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
122   if (!TPC)
123     return Changed;
124 
125   auto &TM = TPC->getTM<PPCTargetMachine>();
126   const PPCSubtarget *Subtarget;
127 
128   for (Function &Func : M) {
129     if (!Func.isDeclaration())
130       continue;
131 
132     if (!isMASSVFunc(Func.getName()))
133       continue;
134 
135     // Call to lowerMASSVCall() invalidates the iterator over users upon
136     // replacing the users. Precomputing the current list of users allows us to
137     // replace all the call sites.
138     SmallVector<User *, 4> MASSVUsers;
139     for (auto *User: Func.users())
140       MASSVUsers.push_back(User);
141 
142     for (auto *User : MASSVUsers) {
143       auto *CI = dyn_cast<CallInst>(User);
144       if (!CI)
145         continue;
146 
147       Subtarget = &TM.getSubtarget<PPCSubtarget>(*CI->getParent()->getParent());
148       Changed |= lowerMASSVCall(CI, Func, M, Subtarget);
149     }
150   }
151 
152   return Changed;
153 }
154 
155 char PPCLowerMASSVEntries::ID = 0;
156 
157 char &llvm::PPCLowerMASSVEntriesID = PPCLowerMASSVEntries::ID;
158 
159 INITIALIZE_PASS(PPCLowerMASSVEntries, DEBUG_TYPE, "Lower MASSV entries", false,
160                 false)
161 
162 ModulePass *llvm::createPPCLowerMASSVEntriesPass() {
163   return new PPCLowerMASSVEntries();
164 }
165