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
  33 #define TLI_DEFINE_VECFUNC(SCAL, VEC, VF, VABI_PREFIX) VEC,
  34 #include "llvm/Analysis/VecFuncs.def"
  35 #undef TLI_DEFINE_MASSV_VECFUNCS
  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 handlePowSpecialCases(CallInst *CI, Function &Func, Module &M);
  58   bool lowerMASSVCall(CallInst *CI, Function &Func, Module &M,
  59                       const PPCSubtarget *Subtarget);
  60 };
  61
  62 } // namespace
  63
  64 /// Checks if the specified function name represents an entry in the MASSV
  65 /// library.
  66 bool PPCLowerMASSVEntries::isMASSVFunc(StringRef Name) {
  67   return llvm::is_contained(MASSVFuncs, Name);
  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 minimum subtarget Power8 for Linux and Power7 for AIX.
  75 StringRef PPCLowerMASSVEntries::getCPUSuffix(const PPCSubtarget *Subtarget) {
  76   // Assume generic when Subtarget is unavailable.
  77   if (!Subtarget)
  78     return "";
  79   // TODO: add _P10 enties to Linux MASS lib and remove the check for AIX
  80   if (Subtarget->isAIXABI() && Subtarget->hasP10Vector())
  81     return "_P10";
  82   if (Subtarget->hasP9Vector())
  83     return "_P9";
  84   if (Subtarget->hasP8Vector())
  85     return "_P8";
  86   if (Subtarget->isAIXABI())
  87     return "_P7";
  88
  89   report_fatal_error(
  90       "Mininum subtarget for -vector-library=MASSV option is Power8 on Linux "
  91       "and Power7 on AIX when vectorization is not disabled.");
  92 }
  93
  94 /// Creates PowerPC subtarget-specific name corresponding to the specified
  95 /// generic MASSV function, and the PowerPC subtarget.
  96 std::string
  97 PPCLowerMASSVEntries::createMASSVFuncName(Function &Func,
  98                                           const PPCSubtarget *Subtarget) {
  99   StringRef Suffix = getCPUSuffix(Subtarget);
 100   auto GenericName = Func.getName().str();
 101   std::string MASSVEntryName = GenericName + Suffix.str();
 102   return MASSVEntryName;
 103 }
 104
 105 /// If there are proper fast-math flags, this function creates llvm.pow
 106 /// intrinsics when the exponent is 0.25 or 0.75.
 107 bool PPCLowerMASSVEntries::handlePowSpecialCases(CallInst *CI, Function &Func,
 108                                                  Module &M) {
 109   if (Func.getName() != "__powf4" && Func.getName() != "__powd2")
 110     return false;
 111
 112   if (Constant *Exp = dyn_cast<Constant>(CI->getArgOperand(1)))
 113     if (ConstantFP *CFP = dyn_cast_or_null<ConstantFP>(Exp->getSplatValue())) {
 114       // If the argument is 0.75 or 0.25 it is cheaper to turn it into pow
 115       // intrinsic so that it could be optimzed as sequence of sqrt's.
 116       if (!CI->hasNoInfs() || !CI->hasApproxFunc())
 117         return false;
 118
 119       if (!CFP->isExactlyValue(0.75) && !CFP->isExactlyValue(0.25))
 120         return false;
 121
 122       if (CFP->isExactlyValue(0.25) && !CI->hasNoSignedZeros())
 123         return false;
 124
 125       CI->setCalledFunction(
 126           Intrinsic::getOrInsertDeclaration(&M, Intrinsic::pow, CI->getType()));
 127       return true;
 128     }
 129
 130   return false;
 131 }
 132
 133 /// Lowers generic MASSV entries to PowerPC subtarget-specific MASSV entries.
 134 /// e.g.: __sind2_massv --> __sind2_P9 for a Power9 subtarget.
 135 /// Both function prototypes and their callsites are updated during lowering.
 136 bool PPCLowerMASSVEntries::lowerMASSVCall(CallInst *CI, Function &Func,
 137                                           Module &M,
 138                                           const PPCSubtarget *Subtarget) {
 139   if (CI->use_empty())
 140     return false;
 141
 142   // Handling pow(x, 0.25), pow(x, 0.75), powf(x, 0.25), powf(x, 0.75)
 143   if (handlePowSpecialCases(CI, Func, M))
 144     return true;
 145
 146   std::string MASSVEntryName = createMASSVFuncName(Func, Subtarget);
 147   FunctionCallee FCache = M.getOrInsertFunction(
 148       MASSVEntryName, Func.getFunctionType(), Func.getAttributes());
 149
 150   CI->setCalledFunction(FCache);
 151
 152   return true;
 153 }
 154
 155 bool PPCLowerMASSVEntries::runOnModule(Module &M) {
 156   bool Changed = false;
 157
 158   auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
 159   if (!TPC)
 160     return Changed;
 161
 162   auto &TM = TPC->getTM<PPCTargetMachine>();
 163   const PPCSubtarget *Subtarget;
 164
 165   for (Function &Func : M) {
 166     if (!Func.isDeclaration())
 167       continue;
 168
 169     if (!isMASSVFunc(Func.getName()))
 170       continue;
 171
 172     // Call to lowerMASSVCall() invalidates the iterator over users upon
 173     // replacing the users. Precomputing the current list of users allows us to
 174     // replace all the call sites.
 175     SmallVector<User *, 4> MASSVUsers(Func.users());
 176
 177     for (auto *User : MASSVUsers) {
 178       auto *CI = dyn_cast<CallInst>(User);
 179       if (!CI)
 180         continue;
 181
 182       Subtarget = &TM.getSubtarget<PPCSubtarget>(*CI->getParent()->getParent());
 183       Changed |= lowerMASSVCall(CI, Func, M, Subtarget);
 184     }
 185   }
 186
 187   return Changed;
 188 }
 189
 190 char PPCLowerMASSVEntries::ID = 0;
 191
 192 char &llvm::PPCLowerMASSVEntriesID = PPCLowerMASSVEntries::ID;
 193
 194 INITIALIZE_PASS(PPCLowerMASSVEntries, DEBUG_TYPE, "Lower MASSV entries", false,
 195                 false)
 196
 197 ModulePass *llvm::createPPCLowerMASSVEntriesPass() {
 198   return new PPCLowerMASSVEntries();
 199 }