src/compiler/codegen/mips/Mips32/Gen.cc

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * This file contains codegen for the Mips ISA and is intended to be
 * includes by:
 *
 *        Codegen-$(TARGET_ARCH_VARIANT).c
 *
 */

#include "oat/runtime/oat_support_entrypoints.h"

namespace art {

void genSpecialCase(CompilationUnit* cUnit, BasicBlock* bb, MIR* mir,
                    SpecialCaseHandler specialCase)
{
    // TODO
}

/*
 * The lack of pc-relative loads on Mips presents somewhat of a challenge
 * for our PIC switch table strategy.  To materialize the current location
 * we'll do a dummy JAL and reference our tables using r_RA as the
 * base register.  Note that r_RA will be used both as the base to
 * locate the switch table data and as the reference base for the switch
 * target offsets stored in the table.  We'll use a special pseudo-instruction
 * to represent the jal and trigger the construction of the
 * switch table offsets (which will happen after final assembly and all
 * labels are fixed).
 *
 * The test loop will look something like:
 *
 *   ori   rEnd, r_ZERO, #tableSize  ; size in bytes
 *   jal   BaseLabel         ; stores "return address" (BaseLabel) in r_RA
 *   nop                     ; opportunistically fill
 * BaseLabel:
 *   addiu rBase, r_RA, <table> - <BaseLabel>  ; table relative to BaseLabel
     addu  rEnd, rEnd, rBase                   ; end of table
 *   lw    rVal, [rSP, vRegOff]                ; Test Value
 * loop:
 *   beq   rBase, rEnd, done
 *   lw    rKey, 0(rBase)
 *   addu  rBase, 8
 *   bne   rVal, rKey, loop
 *   lw    rDisp, -4(rBase)
 *   addu  r_RA, rDisp
 *   jr    r_RA
 * done:
 *
 */
void genSparseSwitch(CompilationUnit* cUnit, uint32_t tableOffset,
                     RegLocation rlSrc, LIR* labelList)
{
  const u2* table = cUnit->insns + cUnit->currentDalvikOffset + tableOffset;
  if (cUnit->printMe) {
    dumpSparseSwitchTable(table);
  }
  // Add the table to the list - we'll process it later
  SwitchTable *tabRec = (SwitchTable *)oatNew(cUnit, sizeof(SwitchTable),
                                              true, kAllocData);
  tabRec->table = table;
  tabRec->vaddr = cUnit->currentDalvikOffset;
  int elements = table[1];
  tabRec->targets = (LIR* *)oatNew(cUnit, elements * sizeof(LIR*), true,
                                   kAllocLIR);
  oatInsertGrowableList(cUnit, &cUnit->switchTables, (intptr_t)tabRec);

  // The table is composed of 8-byte key/disp pairs
  int byteSize = elements * 8;

  int sizeHi = byteSize >> 16;
  int sizeLo = byteSize & 0xffff;

  int rEnd = oatAllocTemp(cUnit);
  if (sizeHi) {
    newLIR2(cUnit, kMipsLui, rEnd, sizeHi);
  }
  // Must prevent code motion for the curr pc pair
  genBarrier(cUnit);  // Scheduling barrier
  newLIR0(cUnit, kMipsCurrPC);  // Really a jal to .+8
  // Now, fill the branch delay slot
  if (sizeHi) {
    newLIR3(cUnit, kMipsOri, rEnd, rEnd, sizeLo);
  } else {
    newLIR3(cUnit, kMipsOri, rEnd, r_ZERO, sizeLo);
  }
  genBarrier(cUnit);  // Scheduling barrier

  // Construct BaseLabel and set up table base register
  LIR* baseLabel = newLIR0(cUnit, kPseudoTargetLabel);
  // Remember base label so offsets can be computed later
  tabRec->anchor = baseLabel;
  int rBase = oatAllocTemp(cUnit);
  newLIR4(cUnit, kMipsDelta, rBase, 0, (intptr_t)baseLabel, (intptr_t)tabRec);
  opRegRegReg(cUnit, kOpAdd, rEnd, rEnd, rBase);

  // Grab switch test value
  rlSrc = loadValue(cUnit, rlSrc, kCoreReg);

  // Test loop
  int rKey = oatAllocTemp(cUnit);
  LIR* loopLabel = newLIR0(cUnit, kPseudoTargetLabel);
  LIR* exitBranch = opCmpBranch(cUnit , kCondEq, rBase, rEnd, NULL);
  loadWordDisp(cUnit, rBase, 0, rKey);
  opRegImm(cUnit, kOpAdd, rBase, 8);
  opCmpBranch(cUnit, kCondNe, rlSrc.lowReg, rKey, loopLabel);
  int rDisp = oatAllocTemp(cUnit);
  loadWordDisp(cUnit, rBase, -4, rDisp);
  opRegRegReg(cUnit, kOpAdd, r_RA, r_RA, rDisp);
  opReg(cUnit, kOpBx, r_RA);

  // Loop exit
  LIR* exitLabel = newLIR0(cUnit, kPseudoTargetLabel);
  exitBranch->target = exitLabel;
}

/*
 * Code pattern will look something like:
 *
 *   lw    rVal
 *   jal   BaseLabel         ; stores "return address" (BaseLabel) in r_RA
 *   nop                     ; opportunistically fill
 *   [subiu rVal, bias]      ; Remove bias if lowVal != 0
 *   bound check -> done
 *   lw    rDisp, [r_RA, rVal]
 *   addu  r_RA, rDisp
 *   jr    r_RA
 * done:
 */
void genPackedSwitch(CompilationUnit* cUnit, uint32_t tableOffset,
                     RegLocation rlSrc)
{
  const u2* table = cUnit->insns + cUnit->currentDalvikOffset + tableOffset;
  if (cUnit->printMe) {
    dumpPackedSwitchTable(table);
  }
  // Add the table to the list - we'll process it later
  SwitchTable *tabRec = (SwitchTable *)oatNew(cUnit, sizeof(SwitchTable),
                        true, kAllocData);
  tabRec->table = table;
  tabRec->vaddr = cUnit->currentDalvikOffset;
  int size = table[1];
  tabRec->targets = (LIR* *)oatNew(cUnit, size * sizeof(LIR*), true,
                    kAllocLIR);
  oatInsertGrowableList(cUnit, &cUnit->switchTables, (intptr_t)tabRec);

  // Get the switch value
  rlSrc = loadValue(cUnit, rlSrc, kCoreReg);

  // Prepare the bias.  If too big, handle 1st stage here
  int lowKey = s4FromSwitchData(&table[2]);
  bool largeBias = false;
  int rKey;
  if (lowKey == 0) {
    rKey = rlSrc.lowReg;
  } else if ((lowKey & 0xffff) != lowKey) {
    rKey = oatAllocTemp(cUnit);
    loadConstant(cUnit, rKey, lowKey);
    largeBias = true;
  } else {
    rKey = oatAllocTemp(cUnit);
  }

  // Must prevent code motion for the curr pc pair
  genBarrier(cUnit);
  newLIR0(cUnit, kMipsCurrPC);  // Really a jal to .+8
  // Now, fill the branch delay slot with bias strip
  if (lowKey == 0) {
    newLIR0(cUnit, kMipsNop);
  } else {
    if (largeBias) {
      opRegRegReg(cUnit, kOpSub, rKey, rlSrc.lowReg, rKey);
    } else {
      opRegRegImm(cUnit, kOpSub, rKey, rlSrc.lowReg, lowKey);
    }
  }
  genBarrier(cUnit);  // Scheduling barrier

  // Construct BaseLabel and set up table base register
  LIR* baseLabel = newLIR0(cUnit, kPseudoTargetLabel);
  // Remember base label so offsets can be computed later
  tabRec->anchor = baseLabel;

  // Bounds check - if < 0 or >= size continue following switch
  LIR* branchOver = opCmpImmBranch(cUnit, kCondHi, rKey, size-1, NULL);

  // Materialize the table base pointer
  int rBase = oatAllocTemp(cUnit);
  newLIR4(cUnit, kMipsDelta, rBase, 0, (intptr_t)baseLabel, (intptr_t)tabRec);

  // Load the displacement from the switch table
  int rDisp = oatAllocTemp(cUnit);
  loadBaseIndexed(cUnit, rBase, rKey, rDisp, 2, kWord);

  // Add to r_AP and go
  opRegRegReg(cUnit, kOpAdd, r_RA, r_RA, rDisp);
  opReg(cUnit, kOpBx, r_RA);

  /* branchOver target here */
  LIR* target = newLIR0(cUnit, kPseudoTargetLabel);
  branchOver->target = (LIR*)target;
}

/*
 * Array data table format:
 *  ushort ident = 0x0300   magic value
 *  ushort width            width of each element in the table
 *  uint   size             number of elements in the table
 *  ubyte  data[size*width] table of data values (may contain a single-byte
 *                          padding at the end)
 *
 * Total size is 4+(width * size + 1)/2 16-bit code units.
 */
void genFillArrayData(CompilationUnit* cUnit, uint32_t tableOffset,
                      RegLocation rlSrc)
{
  const u2* table = cUnit->insns + cUnit->currentDalvikOffset + tableOffset;
  // Add the table to the list - we'll process it later
  FillArrayData *tabRec = (FillArrayData *)
     oatNew(cUnit, sizeof(FillArrayData), true, kAllocData);
  tabRec->table = table;
  tabRec->vaddr = cUnit->currentDalvikOffset;
  u2 width = tabRec->table[1];
  u4 size = tabRec->table[2] | (((u4)tabRec->table[3]) << 16);
  tabRec->size = (size * width) + 8;

  oatInsertGrowableList(cUnit, &cUnit->fillArrayData, (intptr_t)tabRec);

  // Making a call - use explicit registers
  oatFlushAllRegs(cUnit);   /* Everything to home location */
  oatLockCallTemps(cUnit);
  loadValueDirectFixed(cUnit, rlSrc, rARG0);

  // Must prevent code motion for the curr pc pair
  genBarrier(cUnit);
  newLIR0(cUnit, kMipsCurrPC);  // Really a jal to .+8
  // Now, fill the branch delay slot with the helper load
  int rTgt = loadHelper(cUnit, ENTRYPOINT_OFFSET(pHandleFillArrayDataFromCode));
  genBarrier(cUnit);  // Scheduling barrier

  // Construct BaseLabel and set up table base register
  LIR* baseLabel = newLIR0(cUnit, kPseudoTargetLabel);

  // Materialize a pointer to the fill data image
  newLIR4(cUnit, kMipsDelta, rARG1, 0, (intptr_t)baseLabel, (intptr_t)tabRec);

  // And go...
  oatClobberCalleeSave(cUnit);
  opReg(cUnit, kOpBlx, rTgt); // ( array*, fill_data* )
}

void genNegFloat(CompilationUnit *cUnit, RegLocation rlDest, RegLocation rlSrc)
{
  RegLocation rlResult;
  rlSrc = loadValue(cUnit, rlSrc, kCoreReg);
  rlResult = oatEvalLoc(cUnit, rlDest, kCoreReg, true);
  opRegRegImm(cUnit, kOpAdd, rlResult.lowReg, rlSrc.lowReg, 0x80000000);
  storeValue(cUnit, rlDest, rlResult);
}

void genNegDouble(CompilationUnit *cUnit, RegLocation rlDest, RegLocation rlSrc)
{
  RegLocation rlResult;
  rlSrc = loadValueWide(cUnit, rlSrc, kCoreReg);
  rlResult = oatEvalLoc(cUnit, rlDest, kCoreReg, true);
  opRegRegImm(cUnit, kOpAdd, rlResult.highReg, rlSrc.highReg, 0x80000000);
  opRegCopy(cUnit, rlResult.lowReg, rlSrc.lowReg);
  storeValueWide(cUnit, rlDest, rlResult);
}

/*
 * TODO: implement fast path to short-circuit thin-lock case
 */
void genMonitorEnter(CompilationUnit* cUnit, int optFlags, RegLocation rlSrc)
{
  oatFlushAllRegs(cUnit);
  loadValueDirectFixed(cUnit, rlSrc, rARG0);  // Get obj
  oatLockCallTemps(cUnit);  // Prepare for explicit register usage
  genNullCheck(cUnit, rlSrc.sRegLow, rARG0, optFlags);
  // Go expensive route - artLockObjectFromCode(self, obj);
  int rTgt = loadHelper(cUnit, ENTRYPOINT_OFFSET(pLockObjectFromCode));
  oatClobberCalleeSave(cUnit);
  opReg(cUnit, kOpBlx, rTgt);
}

/*
 * TODO: implement fast path to short-circuit thin-lock case
 */
void genMonitorExit(CompilationUnit* cUnit, int optFlags, RegLocation rlSrc)
{
  oatFlushAllRegs(cUnit);
  loadValueDirectFixed(cUnit, rlSrc, rARG0);  // Get obj
  oatLockCallTemps(cUnit);  // Prepare for explicit register usage
  genNullCheck(cUnit, rlSrc.sRegLow, rARG0, optFlags);
  // Go expensive route - UnlockObjectFromCode(obj);
  int rTgt = loadHelper(cUnit, ENTRYPOINT_OFFSET(pUnlockObjectFromCode));
  oatClobberCalleeSave(cUnit);
  opReg(cUnit, kOpBlx, rTgt);
}

/*
 * Compare two 64-bit values
 *    x = y     return  0
 *    x < y     return -1
 *    x > y     return  1
 *
 *    slt   t0,  x.hi, y.hi;        # (x.hi < y.hi) ? 1:0
 *    sgt   t1,  x.hi, y.hi;        # (y.hi > x.hi) ? 1:0
 *    subu  res, t0, t1             # res = -1:1:0 for [ < > = ]
 *    bnez  res, finish
 *    sltu  t0, x.lo, y.lo
 *    sgtu  r1, x.lo, y.lo
 *    subu  res, t0, t1
 * finish:
 *
 */
void genCmpLong(CompilationUnit* cUnit, RegLocation rlDest,
        RegLocation rlSrc1, RegLocation rlSrc2)
{
  rlSrc1 = loadValueWide(cUnit, rlSrc1, kCoreReg);
  rlSrc2 = loadValueWide(cUnit, rlSrc2, kCoreReg);
  int t0 = oatAllocTemp(cUnit);
  int t1 = oatAllocTemp(cUnit);
  RegLocation rlResult = oatEvalLoc(cUnit, rlDest, kCoreReg, true);
  newLIR3(cUnit, kMipsSlt, t0, rlSrc1.highReg, rlSrc2.highReg);
  newLIR3(cUnit, kMipsSlt, t1, rlSrc2.highReg, rlSrc1.highReg);
  newLIR3(cUnit, kMipsSubu, rlResult.lowReg, t1, t0);
  LIR* branch = opCmpImmBranch(cUnit, kCondNe, rlResult.lowReg, 0, NULL);
  newLIR3(cUnit, kMipsSltu, t0, rlSrc1.lowReg, rlSrc2.lowReg);
  newLIR3(cUnit, kMipsSltu, t1, rlSrc2.lowReg, rlSrc1.lowReg);
  newLIR3(cUnit, kMipsSubu, rlResult.lowReg, t1, t0);
  oatFreeTemp(cUnit, t0);
  oatFreeTemp(cUnit, t1);
  LIR* target = newLIR0(cUnit, kPseudoTargetLabel);
  branch->target = (LIR*)target;
  storeValue(cUnit, rlDest, rlResult);
}

LIR* opCmpBranch(CompilationUnit* cUnit, ConditionCode cond, int src1,
         int src2, LIR* target)
{
  LIR* branch;
  MipsOpCode sltOp;
  MipsOpCode brOp;
  bool cmpZero = false;
  bool swapped = false;
  switch (cond) {
    case kCondEq:
      brOp = kMipsBeq;
      cmpZero = true;
      break;
    case kCondNe:
      brOp = kMipsBne;
      cmpZero = true;
      break;
    case kCondCc:
      sltOp = kMipsSltu;
      brOp = kMipsBnez;
      break;
    case kCondCs:
      sltOp = kMipsSltu;
      brOp = kMipsBeqz;
      break;
    case kCondGe:
      sltOp = kMipsSlt;
      brOp = kMipsBeqz;
      break;
    case kCondGt:
      sltOp = kMipsSlt;
      brOp = kMipsBnez;
      swapped = true;
      break;
    case kCondLe:
      sltOp = kMipsSlt;
      brOp = kMipsBeqz;
      swapped = true;
      break;
    case kCondLt:
      sltOp = kMipsSlt;
      brOp = kMipsBnez;
      break;
    case kCondHi:  // Gtu
      sltOp = kMipsSltu;
      brOp = kMipsBnez;
      swapped = true;
      break;
    default:
      LOG(FATAL) << "No support for ConditionCode: " << (int) cond;
      return NULL;
  }
  if (cmpZero) {
    branch = newLIR2(cUnit, brOp, src1, src2);
  } else {
    int tReg = oatAllocTemp(cUnit);
    if (swapped) {
      newLIR3(cUnit, sltOp, tReg, src2, src1);
    } else {
      newLIR3(cUnit, sltOp, tReg, src1, src2);
    }
    branch = newLIR1(cUnit, brOp, tReg);
    oatFreeTemp(cUnit, tReg);
  }
  branch->target = target;
  return branch;
}

LIR* opCmpImmBranch(CompilationUnit* cUnit, ConditionCode cond, int reg,
          int checkValue, LIR* target)
{
  LIR* branch;
  if (checkValue != 0) {
    // TUNING: handle s16 & kCondLt/Mi case using slti
    int tReg = oatAllocTemp(cUnit);
    loadConstant(cUnit, tReg, checkValue);
    branch = opCmpBranch(cUnit, cond, reg, tReg, target);
    oatFreeTemp(cUnit, tReg);
    return branch;
  }
  MipsOpCode opc;
  switch (cond) {
    case kCondEq: opc = kMipsBeqz; break;
    case kCondGe: opc = kMipsBgez; break;
    case kCondGt: opc = kMipsBgtz; break;
    case kCondLe: opc = kMipsBlez; break;
    //case KCondMi:
    case kCondLt: opc = kMipsBltz; break;
    case kCondNe: opc = kMipsBnez; break;
    default:
      // Tuning: use slti when applicable
      int tReg = oatAllocTemp(cUnit);
      loadConstant(cUnit, tReg, checkValue);
      branch = opCmpBranch(cUnit, cond, reg, tReg, target);
      oatFreeTemp(cUnit, tReg);
      return branch;
  }
  branch = newLIR1(cUnit, opc, reg);
  branch->target = target;
  return branch;
}

LIR* opRegCopyNoInsert(CompilationUnit *cUnit, int rDest, int rSrc)
{
#ifdef __mips_hard_float
  if (FPREG(rDest) || FPREG(rSrc))
    return fpRegCopy(cUnit, rDest, rSrc);
#endif
  LIR* res = rawLIR(cUnit, cUnit->currentDalvikOffset, kMipsMove,
            rDest, rSrc);
  if (!(cUnit->disableOpt & (1 << kSafeOptimizations)) && rDest == rSrc) {
    res->flags.isNop = true;
  }
  return res;
}

LIR* opRegCopy(CompilationUnit *cUnit, int rDest, int rSrc)
{
  LIR *res = opRegCopyNoInsert(cUnit, rDest, rSrc);
  oatAppendLIR(cUnit, (LIR*)res);
  return res;
}

void opRegCopyWide(CompilationUnit *cUnit, int destLo, int destHi,
          int srcLo, int srcHi)
{
#ifdef __mips_hard_float
  bool destFP = FPREG(destLo) && FPREG(destHi);
  bool srcFP = FPREG(srcLo) && FPREG(srcHi);
  assert(FPREG(srcLo) == FPREG(srcHi));
  assert(FPREG(destLo) == FPREG(destHi));
  if (destFP) {
    if (srcFP) {
      opRegCopy(cUnit, S2D(destLo, destHi), S2D(srcLo, srcHi));
    } else {
       /* note the operands are swapped for the mtc1 instr */
      newLIR2(cUnit, kMipsMtc1, srcLo, destLo);
      newLIR2(cUnit, kMipsMtc1, srcHi, destHi);
    }
  } else {
    if (srcFP) {
      newLIR2(cUnit, kMipsMfc1, destLo, srcLo);
      newLIR2(cUnit, kMipsMfc1, destHi, srcHi);
    } else {
      // Handle overlap
      if (srcHi == destLo) {
        opRegCopy(cUnit, destHi, srcHi);
        opRegCopy(cUnit, destLo, srcLo);
      } else {
        opRegCopy(cUnit, destLo, srcLo);
        opRegCopy(cUnit, destHi, srcHi);
      }
    }
  }
#else
  // Handle overlap
  if (srcHi == destLo) {
    opRegCopy(cUnit, destHi, srcHi);
    opRegCopy(cUnit, destLo, srcLo);
  } else {
    opRegCopy(cUnit, destLo, srcLo);
    opRegCopy(cUnit, destHi, srcHi);
  }
#endif
}

}  // namespace art