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//===-- PPCLowerMASSVEntries.cpp ------------------------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file implements lowering of MASSV (SIMD) entries for specific PowerPC
// subtargets.
// Following is an example of a conversion specific to Power9 subtarget:
// __sind2_massv ---> __sind2_P9
#include "PPC.h"
#include "PPCSubtarget.h"
#include "PPCTargetMachine.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#define DEBUG_TYPE "ppc-lower-massv-entries"
using namespace llvm;
namespace {
// Length of the suffix "massv", which is specific to IBM MASSV library entries.
const unsigned MASSVSuffixLength = 2;
static StringRef MASSVFuncs[] = {
#include "llvm/Analysis/VecFuncs.def"
class PPCLowerMASSVEntries : public ModulePass {
static char ID;
PPCLowerMASSVEntries() : ModulePass(ID) {}
bool runOnModule(Module &M) override;
StringRef getPassName() const override { return "PPC Lower MASS Entries"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
static bool isMASSVFunc(StringRef Name);
static StringRef getCPUSuffix(const PPCSubtarget *Subtarget);
static std::string createMASSVFuncName(Function &Func,
const PPCSubtarget *Subtarget);
bool handlePowSpecialCases(CallInst *CI, Function &Func, Module &M);
bool lowerMASSVCall(CallInst *CI, Function &Func, Module &M,
const PPCSubtarget *Subtarget);
} // namespace
/// Checks if the specified function name represents an entry in the MASSV
/// library.
bool PPCLowerMASSVEntries::isMASSVFunc(StringRef Name) {
return llvm::is_contained(MASSVFuncs, Name);
/// Returns a string corresponding to the specified PowerPC subtarget. e.g.:
/// "P8" for Power8, "P9" for Power9. The string is used as a suffix while
/// generating subtarget-specific MASSV library functions. Current support
/// includes Power8 and Power9 subtargets.
StringRef PPCLowerMASSVEntries::getCPUSuffix(const PPCSubtarget *Subtarget) {
// Assume Power8 when Subtarget is unavailable.
if (!Subtarget)
return "P8";
if (Subtarget->hasP9Vector())
return "P9";
if (Subtarget->hasP8Vector())
return "P8";
report_fatal_error("Unsupported Subtarget: MASSV is supported only on "
"Power8 and Power9 subtargets.");
/// Creates PowerPC subtarget-specific name corresponding to the specified
/// generic MASSV function, and the PowerPC subtarget.
PPCLowerMASSVEntries::createMASSVFuncName(Function &Func,
const PPCSubtarget *Subtarget) {
StringRef Suffix = getCPUSuffix(Subtarget);
auto GenericName = Func.getName().drop_back(MASSVSuffixLength).str();
std::string MASSVEntryName = GenericName + Suffix.str();
return MASSVEntryName;
/// If there are proper fast-math flags, this function creates llvm.pow
/// intrinsics when the exponent is 0.25 or 0.75.
bool PPCLowerMASSVEntries::handlePowSpecialCases(CallInst *CI, Function &Func,
Module &M) {
if (Func.getName() != "__powf4_P8" && Func.getName() != "__powd2_P8")
return false;
if (Constant *Exp = dyn_cast<Constant>(CI->getArgOperand(1)))
if (ConstantFP *CFP = dyn_cast_or_null<ConstantFP>(Exp->getSplatValue())) {
// If the argument is 0.75 or 0.25 it is cheaper to turn it into pow
// intrinsic so that it could be optimzed as sequence of sqrt's.
if (!CI->hasNoInfs() || !CI->hasApproxFunc())
return false;
if (!CFP->isExactlyValue(0.75) && !CFP->isExactlyValue(0.25))
return false;
if (CFP->isExactlyValue(0.25) && !CI->hasNoSignedZeros())
return false;
Intrinsic::getDeclaration(&M, Intrinsic::pow, CI->getType()));
return true;
return false;
/// Lowers generic MASSV entries to PowerPC subtarget-specific MASSV entries.
/// e.g.: __sind2_massv --> __sind2_P9 for a Power9 subtarget.
/// Both function prototypes and their callsites are updated during lowering.
bool PPCLowerMASSVEntries::lowerMASSVCall(CallInst *CI, Function &Func,
Module &M,
const PPCSubtarget *Subtarget) {
if (CI->use_empty())
return false;
// Handling pow(x, 0.25), pow(x, 0.75), powf(x, 0.25), powf(x, 0.75)
if (handlePowSpecialCases(CI, Func, M))
return true;
std::string MASSVEntryName = createMASSVFuncName(Func, Subtarget);
FunctionCallee FCache = M.getOrInsertFunction(
MASSVEntryName, Func.getFunctionType(), Func.getAttributes());
return true;
bool PPCLowerMASSVEntries::runOnModule(Module &M) {
bool Changed = false;
auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
if (!TPC)
return Changed;
auto &TM = TPC->getTM<PPCTargetMachine>();
const PPCSubtarget *Subtarget;
for (Function &Func : M) {
if (!Func.isDeclaration())
if (!isMASSVFunc(Func.getName()))
// Call to lowerMASSVCall() invalidates the iterator over users upon
// replacing the users. Precomputing the current list of users allows us to
// replace all the call sites.
SmallVector<User *, 4> MASSVUsers(Func.users());
for (auto *User : MASSVUsers) {
auto *CI = dyn_cast<CallInst>(User);
if (!CI)
Subtarget = &TM.getSubtarget<PPCSubtarget>(*CI->getParent()->getParent());
Changed |= lowerMASSVCall(CI, Func, M, Subtarget);
return Changed;
char PPCLowerMASSVEntries::ID = 0;
char &llvm::PPCLowerMASSVEntriesID = PPCLowerMASSVEntries::ID;
INITIALIZE_PASS(PPCLowerMASSVEntries, DEBUG_TYPE, "Lower MASSV entries", false,
ModulePass *llvm::createPPCLowerMASSVEntriesPass() {
return new PPCLowerMASSVEntries();