lib/Target/X86/X86ShuffleDecode.h

//===-- X86ShuffleDecode.h - X86 shuffle decode logic ---------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Define several functions to decode x86 specific shuffle semantics into a
// generic vector mask.
//
//===----------------------------------------------------------------------===//

#ifndef X86_SHUFFLE_DECODE_H
#define X86_SHUFFLE_DECODE_H

#include "llvm/ADT/SmallVector.h"
using namespace llvm;

//===----------------------------------------------------------------------===//
//  Vector Mask Decoding
//===----------------------------------------------------------------------===//

enum {
  SM_SentinelZero = ~0U
};

static void DecodeINSERTPSMask(unsigned Imm,
                               SmallVectorImpl<unsigned> &ShuffleMask) {
  // Defaults the copying the dest value.
  ShuffleMask.push_back(0);
  ShuffleMask.push_back(1);
  ShuffleMask.push_back(2);
  ShuffleMask.push_back(3);

  // Decode the immediate.
  unsigned ZMask = Imm & 15;
  unsigned CountD = (Imm >> 4) & 3;
  unsigned CountS = (Imm >> 6) & 3;

  // CountS selects which input element to use.
  unsigned InVal = 4+CountS;
  // CountD specifies which element of destination to update.
  ShuffleMask[CountD] = InVal;
  // ZMask zaps values, potentially overriding the CountD elt.
  if (ZMask & 1) ShuffleMask[0] = SM_SentinelZero;
  if (ZMask & 2) ShuffleMask[1] = SM_SentinelZero;
  if (ZMask & 4) ShuffleMask[2] = SM_SentinelZero;
  if (ZMask & 8) ShuffleMask[3] = SM_SentinelZero;
}

static void DecodeMOVHLPSMask(SmallVectorImpl<unsigned> &ShuffleMask) {
  ShuffleMask.push_back(3);
  ShuffleMask.push_back(1);
}

static void DecodeMOVLHPSMask(SmallVectorImpl<unsigned> &ShuffleMask) {
  ShuffleMask.push_back(0);
  ShuffleMask.push_back(2);
}

static void DecodePSHUFMask(unsigned NElts, unsigned Imm,
                            SmallVectorImpl<unsigned> &ShuffleMask) {
  for (unsigned i = 0; i != NElts; ++i) {
    ShuffleMask.push_back(Imm % NElts);
    Imm /= NElts;
  }
}

static void DecodePSHUFHWMask(unsigned Imm,
                              SmallVectorImpl<unsigned> &ShuffleMask) {
  ShuffleMask.push_back(0);
  ShuffleMask.push_back(1);
  ShuffleMask.push_back(2);
  ShuffleMask.push_back(3);
  for (unsigned i = 0; i != 4; ++i) {
    ShuffleMask.push_back(4+(Imm & 3));
    Imm >>= 2;
  }
}

static void DecodePSHUFLWMask(unsigned Imm,
                              SmallVectorImpl<unsigned> &ShuffleMask) {
  for (unsigned i = 0; i != 4; ++i) {
    ShuffleMask.push_back((Imm & 3));
    Imm >>= 2;
  }
  ShuffleMask.push_back(4);
  ShuffleMask.push_back(5);
  ShuffleMask.push_back(6);
  ShuffleMask.push_back(7);
}

static void DecodePUNPCKLMask(unsigned NElts,
                              SmallVectorImpl<unsigned> &ShuffleMask) {
  for (unsigned i = 0; i != NElts/2; ++i) {
    ShuffleMask.push_back(i);
    ShuffleMask.push_back(i+NElts);
  }
}

static void DecodePUNPCKHMask(unsigned NElts,
                              SmallVectorImpl<unsigned> &ShuffleMask) {
  for (unsigned i = 0; i != NElts/2; ++i) {
    ShuffleMask.push_back(i+NElts/2);
    ShuffleMask.push_back(i+NElts+NElts/2);
  }
}

static void DecodeSHUFPSMask(unsigned NElts, unsigned Imm,
                             SmallVectorImpl<unsigned> &ShuffleMask) {
  // Part that reads from dest.
  for (unsigned i = 0; i != NElts/2; ++i) {
    ShuffleMask.push_back(Imm % NElts);
    Imm /= NElts;
  }
  // Part that reads from src.
  for (unsigned i = 0; i != NElts/2; ++i) {
    ShuffleMask.push_back(Imm % NElts + NElts);
    Imm /= NElts;
  }
}

static void DecodeUNPCKHPMask(unsigned NElts,
                              SmallVectorImpl<unsigned> &ShuffleMask) {
  for (unsigned i = 0; i != NElts/2; ++i) {
    ShuffleMask.push_back(i+NElts/2);        // Reads from dest
    ShuffleMask.push_back(i+NElts+NElts/2);  // Reads from src
  }
}


/// DecodeUNPCKLPMask - This decodes the shuffle masks for unpcklps/unpcklpd
/// etc.  NElts indicates the number of elements in the vector allowing it to
/// handle different datatypes and vector widths.
static void DecodeUNPCKLPMask(unsigned NElts,
                              SmallVectorImpl<unsigned> &ShuffleMask) {
  for (unsigned i = 0; i != NElts/2; ++i) {
    ShuffleMask.push_back(i);        // Reads from dest
    ShuffleMask.push_back(i+NElts);  // Reads from src
  }
}

#endif