llvm/lib/Target/PowerPC/PPCLowerMASSVEntries.cpp

   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/ADT/STLExtras.h"
  20 #include "llvm/Analysis/TargetTransformInfo.h"
  21 #include "llvm/CodeGen/TargetPassConfig.h"
  22 #include "llvm/IR/Instructions.h"
  23 #include "llvm/IR/Module.h"
  24
  25 #define DEBUG_TYPE "ppc-lower-massv-entries"
  26
  27 using namespace llvm;
  28
  29 namespace {
  30
  31 static StringRef MASSVFuncs[] = {
  32 #define TLI_DEFINE_MASSV_VECFUNCS_NAMES
  33 #include "llvm/Analysis/VecFuncs.def"
  34 };
  35
  36 class PPCLowerMASSVEntries : public ModulePass {
  37 public:
  38   static char ID;
  39
  40   PPCLowerMASSVEntries() : ModulePass(ID) {}
  41
  42   bool runOnModule(Module &M) override;
  43
  44   StringRef getPassName() const override { return "PPC Lower MASS Entries"; }
  45
  46   void getAnalysisUsage(AnalysisUsage &AU) const override {
  47     AU.addRequired<TargetTransformInfoWrapperPass>();
  48   }
  49
  50 private:
  51   static bool isMASSVFunc(StringRef Name);
  52   static StringRef getCPUSuffix(const PPCSubtarget *Subtarget);
  53   static std::string createMASSVFuncName(Function &Func,
  54                                          const PPCSubtarget *Subtarget);
  55   bool handlePowSpecialCases(CallInst *CI, Function &Func, Module &M);
  56   bool lowerMASSVCall(CallInst *CI, Function &Func, Module &M,
  57                       const PPCSubtarget *Subtarget);
  58 };
  59
  60 } // namespace
  61
  62 /// Checks if the specified function name represents an entry in the MASSV
  63 /// library.
  64 bool PPCLowerMASSVEntries::isMASSVFunc(StringRef Name) {
  65   return llvm::is_contained(MASSVFuncs, Name);
  66 }
  67
  68 // FIXME:
  69 /// Returns a string corresponding to the specified PowerPC subtarget. e.g.:
  70 /// "_P8" for Power8, "_P9" for Power9. The string is used as a suffix while
  71 /// generating subtarget-specific MASSV library functions. Current support
  72 /// includes minimum subtarget Power8 for Linux and Power7 for AIX.
  73 StringRef PPCLowerMASSVEntries::getCPUSuffix(const PPCSubtarget *Subtarget) {
  74   // Assume generic when Subtarget is unavailable.
  75   if (!Subtarget)
  76     return "";
  77   // TODO: add _P10 enties to Linux MASS lib and remove the check for AIX
  78   if (Subtarget->isAIXABI() && Subtarget->hasP10Vector())
  79     return "_P10";
  80   if (Subtarget->hasP9Vector())
  81     return "_P9";
  82   if (Subtarget->hasP8Vector())
  83     return "_P8";
  84   if (Subtarget->isAIXABI())
  85     return "_P7";
  86
  87   report_fatal_error(
  88       "Mininum subtarget for -vector-library=MASSV option is Power8 on Linux "
  89       "and Power7 on AIX when vectorization is not disabled.");
  90 }
  91
  92 /// Creates PowerPC subtarget-specific name corresponding to the specified
  93 /// generic MASSV function, and the PowerPC subtarget.
  94 std::string
  95 PPCLowerMASSVEntries::createMASSVFuncName(Function &Func,
  96                                           const PPCSubtarget *Subtarget) {
  97   StringRef Suffix = getCPUSuffix(Subtarget);
  98   auto GenericName = Func.getName().str();
  99   std::string MASSVEntryName = GenericName + Suffix.str();
 100   return MASSVEntryName;
 101 }
 102
 103 /// If there are proper fast-math flags, this function creates llvm.pow
 104 /// intrinsics when the exponent is 0.25 or 0.75.
 105 bool PPCLowerMASSVEntries::handlePowSpecialCases(CallInst *CI, Function &Func,
 106                                                  Module &M) {
 107   if (Func.getName() != "__powf4" && Func.getName() != "__powd2")
 108     return false;
 109
 110   if (Constant *Exp = dyn_cast<Constant>(CI->getArgOperand(1)))
 111     if (ConstantFP *CFP = dyn_cast_or_null<ConstantFP>(Exp->getSplatValue())) {
 112       // If the argument is 0.75 or 0.25 it is cheaper to turn it into pow
 113       // intrinsic so that it could be optimzed as sequence of sqrt's.
 114       if (!CI->hasNoInfs() || !CI->hasApproxFunc())
 115         return false;
 116
 117       if (!CFP->isExactlyValue(0.75) && !CFP->isExactlyValue(0.25))
 118         return false;
 119
 120       if (CFP->isExactlyValue(0.25) && !CI->hasNoSignedZeros())
 121         return false;
 122
 123       CI->setCalledFunction(
 124           Intrinsic::getDeclaration(&M, Intrinsic::pow, CI->getType()));
 125       return true;
 126     }
 127
 128   return false;
 129 }
 130
 131 /// Lowers generic MASSV entries to PowerPC subtarget-specific MASSV entries.
 132 /// e.g.: __sind2_massv --> __sind2_P9 for a Power9 subtarget.
 133 /// Both function prototypes and their callsites are updated during lowering.
 134 bool PPCLowerMASSVEntries::lowerMASSVCall(CallInst *CI, Function &Func,
 135                                           Module &M,
 136                                           const PPCSubtarget *Subtarget) {
 137   if (CI->use_empty())
 138     return false;
 139
 140   // Handling pow(x, 0.25), pow(x, 0.75), powf(x, 0.25), powf(x, 0.75)
 141   if (handlePowSpecialCases(CI, Func, M))
 142     return true;
 143
 144   std::string MASSVEntryName = createMASSVFuncName(Func, Subtarget);
 145   FunctionCallee FCache = M.getOrInsertFunction(
 146       MASSVEntryName, Func.getFunctionType(), Func.getAttributes());
 147
 148   CI->setCalledFunction(FCache);
 149
 150   return true;
 151 }
 152
 153 bool PPCLowerMASSVEntries::runOnModule(Module &M) {
 154   bool Changed = false;
 155
 156   auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
 157   if (!TPC)
 158     return Changed;
 159
 160   auto &TM = TPC->getTM<PPCTargetMachine>();
 161   const PPCSubtarget *Subtarget;
 162
 163   for (Function &Func : M) {
 164     if (!Func.isDeclaration())
 165       continue;
 166
 167     if (!isMASSVFunc(Func.getName()))
 168       continue;
 169
 170     // Call to lowerMASSVCall() invalidates the iterator over users upon
 171     // replacing the users. Precomputing the current list of users allows us to
 172     // replace all the call sites.
 173     SmallVector<User *, 4> MASSVUsers(Func.users());
 174
 175     for (auto *User : MASSVUsers) {
 176       auto *CI = dyn_cast<CallInst>(User);
 177       if (!CI)
 178         continue;
 179
 180       Subtarget = &TM.getSubtarget<PPCSubtarget>(*CI->getParent()->getParent());
 181       Changed |= lowerMASSVCall(CI, Func, M, Subtarget);
 182     }
 183   }
 184
 185   return Changed;
 186 }
 187
 188 char PPCLowerMASSVEntries::ID = 0;
 189
 190 char &llvm::PPCLowerMASSVEntriesID = PPCLowerMASSVEntries::ID;
 191
 192 INITIALIZE_PASS(PPCLowerMASSVEntries, DEBUG_TYPE, "Lower MASSV entries", false,
 193                 false)
 194
 195 ModulePass *llvm::createPPCLowerMASSVEntriesPass() {
 196   return new PPCLowerMASSVEntries();
 197 }