| /* |
| * Copyright (C) 2011 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. |
| */ |
| |
| #include "../../Dalvik.h" |
| #include "../../CompilerInternals.h" |
| #include "ArmLIR.h" |
| #include "Codegen.h" |
| |
| namespace art { |
| |
| #define DEBUG_OPT(X) |
| |
| /* Check RAW, WAR, and WAR dependency on the register operands */ |
| #define CHECK_REG_DEP(use, def, check) ((def & check->useMask) || \ |
| ((use | def) & check->defMask)) |
| |
| /* Scheduler heuristics */ |
| #define MAX_HOIST_DISTANCE 20 |
| #define LDLD_DISTANCE 4 |
| #define LD_LATENCY 2 |
| |
| STATIC inline bool isDalvikRegisterClobbered(ArmLIR* lir1, ArmLIR* lir2) |
| { |
| int reg1Lo = DECODE_ALIAS_INFO_REG(lir1->aliasInfo); |
| int reg1Hi = reg1Lo + DECODE_ALIAS_INFO_WIDE(lir1->aliasInfo); |
| int reg2Lo = DECODE_ALIAS_INFO_REG(lir2->aliasInfo); |
| int reg2Hi = reg2Lo + DECODE_ALIAS_INFO_WIDE(lir2->aliasInfo); |
| |
| return (reg1Lo == reg2Lo) || (reg1Lo == reg2Hi) || (reg1Hi == reg2Lo); |
| } |
| |
| /* Convert a more expensive instruction (ie load) into a move */ |
| STATIC void convertMemOpIntoMove(CompilationUnit* cUnit, ArmLIR* origLIR, |
| int dest, int src) |
| { |
| /* Insert a move to replace the load */ |
| ArmLIR* moveLIR; |
| moveLIR = oatRegCopyNoInsert( cUnit, dest, src); |
| /* |
| * Insert the converted instruction after the original since the |
| * optimization is scannng in the top-down order and the new instruction |
| * will need to be re-checked (eg the new dest clobbers the src used in |
| * thisLIR). |
| */ |
| oatInsertLIRAfter((LIR*) origLIR, (LIR*) moveLIR); |
| } |
| |
| /* |
| * Perform a pass of top-down walk, from the second-last instruction in the |
| * superblock, to eliminate redundant loads and stores. |
| * |
| * An earlier load can eliminate a later load iff |
| * 1) They are must-aliases |
| * 2) The native register is not clobbered in between |
| * 3) The memory location is not written to in between |
| * |
| * An earlier store can eliminate a later load iff |
| * 1) They are must-aliases |
| * 2) The native register is not clobbered in between |
| * 3) The memory location is not written to in between |
| * |
| * A later store can be eliminated by an earlier store iff |
| * 1) They are must-aliases |
| * 2) The memory location is not written to in between |
| */ |
| STATIC void applyLoadStoreElimination(CompilationUnit* cUnit, |
| ArmLIR* headLIR, |
| ArmLIR* tailLIR) |
| { |
| ArmLIR* thisLIR; |
| |
| if (headLIR == tailLIR) return; |
| |
| for (thisLIR = PREV_LIR(tailLIR); |
| thisLIR != headLIR; |
| thisLIR = PREV_LIR(thisLIR)) { |
| int sinkDistance = 0; |
| |
| /* Skip non-interesting instructions */ |
| if ((thisLIR->flags.isNop == true) || |
| isPseudoOpcode(thisLIR->opcode) || |
| !(EncodingMap[thisLIR->opcode].flags & (IS_LOAD | IS_STORE))) { |
| continue; |
| } |
| |
| int nativeRegId = thisLIR->operands[0]; |
| bool isThisLIRLoad = EncodingMap[thisLIR->opcode].flags & IS_LOAD; |
| ArmLIR* checkLIR; |
| /* Use the mem mask to determine the rough memory location */ |
| u8 thisMemMask = (thisLIR->useMask | thisLIR->defMask) & ENCODE_MEM; |
| |
| /* |
| * Currently only eliminate redundant ld/st for constant and Dalvik |
| * register accesses. |
| */ |
| if (!(thisMemMask & (ENCODE_LITERAL | ENCODE_DALVIK_REG))) continue; |
| |
| /* |
| * Add r15 (pc) to the resource mask to prevent this instruction |
| * from sinking past branch instructions. Also take out the memory |
| * region bits since stopMask is used to check data/control |
| * dependencies. |
| */ |
| u8 stopUseRegMask = (ENCODE_REG_PC | thisLIR->useMask) & |
| ~ENCODE_MEM; |
| u8 stopDefRegMask = thisLIR->defMask & ~ENCODE_MEM; |
| |
| for (checkLIR = NEXT_LIR(thisLIR); |
| checkLIR != tailLIR; |
| checkLIR = NEXT_LIR(checkLIR)) { |
| |
| /* |
| * Skip already dead instructions (whose dataflow information is |
| * outdated and misleading). |
| */ |
| if (checkLIR->flags.isNop) continue; |
| |
| u8 checkMemMask = (checkLIR->useMask | checkLIR->defMask) & |
| ENCODE_MEM; |
| u8 aliasCondition = thisMemMask & checkMemMask; |
| bool stopHere = false; |
| |
| /* |
| * Potential aliases seen - check the alias relations |
| */ |
| if (checkMemMask != ENCODE_MEM && aliasCondition != 0) { |
| bool isCheckLIRLoad = EncodingMap[checkLIR->opcode].flags & |
| IS_LOAD; |
| if (aliasCondition == ENCODE_LITERAL) { |
| /* |
| * Should only see literal loads in the instruction |
| * stream. |
| */ |
| DCHECK(!(EncodingMap[checkLIR->opcode].flags & |
| IS_STORE)); |
| /* Same value && same register type */ |
| if (checkLIR->aliasInfo == thisLIR->aliasInfo && |
| REGTYPE(checkLIR->operands[0]) == REGTYPE(nativeRegId)){ |
| /* |
| * Different destination register - insert |
| * a move |
| */ |
| if (checkLIR->operands[0] != nativeRegId) { |
| convertMemOpIntoMove(cUnit, checkLIR, |
| checkLIR->operands[0], |
| nativeRegId); |
| } |
| checkLIR->flags.isNop = true; |
| } |
| } else if (aliasCondition == ENCODE_DALVIK_REG) { |
| /* Must alias */ |
| if (checkLIR->aliasInfo == thisLIR->aliasInfo) { |
| /* Only optimize compatible registers */ |
| bool regCompatible = |
| REGTYPE(checkLIR->operands[0]) == |
| REGTYPE(nativeRegId); |
| if ((isThisLIRLoad && isCheckLIRLoad) || |
| (!isThisLIRLoad && isCheckLIRLoad)) { |
| /* RAR or RAW */ |
| if (regCompatible) { |
| /* |
| * Different destination register - |
| * insert a move |
| */ |
| if (checkLIR->operands[0] != |
| nativeRegId) { |
| convertMemOpIntoMove(cUnit, |
| checkLIR, |
| checkLIR->operands[0], |
| nativeRegId); |
| } |
| checkLIR->flags.isNop = true; |
| } else { |
| /* |
| * Destinaions are of different types - |
| * something complicated going on so |
| * stop looking now. |
| */ |
| stopHere = true; |
| } |
| } else if (isThisLIRLoad && !isCheckLIRLoad) { |
| /* WAR - register value is killed */ |
| stopHere = true; |
| } else if (!isThisLIRLoad && !isCheckLIRLoad) { |
| /* WAW - nuke the earlier store */ |
| thisLIR->flags.isNop = true; |
| stopHere = true; |
| } |
| /* Partial overlap */ |
| } else if (isDalvikRegisterClobbered(thisLIR, checkLIR)) { |
| /* |
| * It is actually ok to continue if checkLIR |
| * is a read. But it is hard to make a test |
| * case for this so we just stop here to be |
| * conservative. |
| */ |
| stopHere = true; |
| } |
| } |
| /* Memory content may be updated. Stop looking now. */ |
| if (stopHere) { |
| break; |
| /* The checkLIR has been transformed - check the next one */ |
| } else if (checkLIR->flags.isNop) { |
| continue; |
| } |
| } |
| |
| |
| /* |
| * this and check LIRs have no memory dependency. Now check if |
| * their register operands have any RAW, WAR, and WAW |
| * dependencies. If so, stop looking. |
| */ |
| if (stopHere == false) { |
| stopHere = CHECK_REG_DEP(stopUseRegMask, stopDefRegMask, |
| checkLIR); |
| } |
| |
| if (stopHere == true) { |
| DEBUG_OPT(dumpDependentInsnPair(thisLIR, checkLIR, |
| "REG CLOBBERED")); |
| /* Only sink store instructions */ |
| if (sinkDistance && !isThisLIRLoad) { |
| ArmLIR* newStoreLIR = |
| (ArmLIR* ) oatNew(sizeof(ArmLIR), true, kAllocLIR); |
| *newStoreLIR = *thisLIR; |
| /* |
| * Stop point found - insert *before* the checkLIR |
| * since the instruction list is scanned in the |
| * top-down order. |
| */ |
| oatInsertLIRBefore((LIR*) checkLIR, |
| (LIR*) newStoreLIR); |
| thisLIR->flags.isNop = true; |
| } |
| break; |
| } else if (!checkLIR->flags.isNop) { |
| sinkDistance++; |
| } |
| } |
| } |
| } |
| |
| /* |
| * Perform a pass of bottom-up walk, from the second instruction in the |
| * superblock, to try to hoist loads to earlier slots. |
| */ |
| STATIC void applyLoadHoisting(CompilationUnit* cUnit, |
| ArmLIR* headLIR, |
| ArmLIR* tailLIR) |
| { |
| ArmLIR* thisLIR, *checkLIR; |
| /* |
| * Store the list of independent instructions that can be hoisted past. |
| * Will decide the best place to insert later. |
| */ |
| ArmLIR* prevInstList[MAX_HOIST_DISTANCE]; |
| |
| /* Empty block */ |
| if (headLIR == tailLIR) return; |
| |
| /* Start from the second instruction */ |
| for (thisLIR = NEXT_LIR(headLIR); |
| thisLIR != tailLIR; |
| thisLIR = NEXT_LIR(thisLIR)) { |
| |
| /* Skip non-interesting instructions */ |
| if ((thisLIR->flags.isNop == true) || |
| isPseudoOpcode(thisLIR->opcode) || |
| !(EncodingMap[thisLIR->opcode].flags & IS_LOAD)) { |
| continue; |
| } |
| |
| u8 stopUseAllMask = thisLIR->useMask; |
| |
| /* |
| * Branches for null/range checks are marked with the true resource |
| * bits, and loads to Dalvik registers, constant pools, and non-alias |
| * locations are safe to be hoisted. So only mark the heap references |
| * conservatively here. |
| */ |
| if (stopUseAllMask & ENCODE_HEAP_REF) { |
| stopUseAllMask |= ENCODE_REG_PC; |
| } |
| |
| /* Similar as above, but just check for pure register dependency */ |
| u8 stopUseRegMask = stopUseAllMask & ~ENCODE_MEM; |
| u8 stopDefRegMask = thisLIR->defMask & ~ENCODE_MEM; |
| |
| int nextSlot = 0; |
| bool stopHere = false; |
| |
| /* Try to hoist the load to a good spot */ |
| for (checkLIR = PREV_LIR(thisLIR); |
| checkLIR != headLIR; |
| checkLIR = PREV_LIR(checkLIR)) { |
| |
| /* |
| * Skip already dead instructions (whose dataflow information is |
| * outdated and misleading). |
| */ |
| if (checkLIR->flags.isNop) continue; |
| |
| u8 checkMemMask = checkLIR->defMask & ENCODE_MEM; |
| u8 aliasCondition = stopUseAllMask & checkMemMask; |
| stopHere = false; |
| |
| /* Potential WAR alias seen - check the exact relation */ |
| if (checkMemMask != ENCODE_MEM && aliasCondition != 0) { |
| /* We can fully disambiguate Dalvik references */ |
| if (aliasCondition == ENCODE_DALVIK_REG) { |
| /* Must alias or partually overlap */ |
| if ((checkLIR->aliasInfo == thisLIR->aliasInfo) || |
| isDalvikRegisterClobbered(thisLIR, checkLIR)) { |
| stopHere = true; |
| } |
| /* Conservatively treat all heap refs as may-alias */ |
| } else { |
| DCHECK_EQ(aliasCondition, ENCODE_HEAP_REF); |
| stopHere = true; |
| } |
| /* Memory content may be updated. Stop looking now. */ |
| if (stopHere) { |
| prevInstList[nextSlot++] = checkLIR; |
| break; |
| } |
| } |
| |
| if (stopHere == false) { |
| stopHere = CHECK_REG_DEP(stopUseRegMask, stopDefRegMask, |
| checkLIR); |
| } |
| |
| /* |
| * Store the dependent or non-pseudo/indepedent instruction to the |
| * list. |
| */ |
| if (stopHere || !isPseudoOpcode(checkLIR->opcode)) { |
| prevInstList[nextSlot++] = checkLIR; |
| if (nextSlot == MAX_HOIST_DISTANCE) break; |
| } |
| |
| /* Found a new place to put the load - move it here */ |
| if (stopHere == true) { |
| DEBUG_OPT(dumpDependentInsnPair(checkLIR, thisLIR |
| "HOIST STOP")); |
| break; |
| } |
| } |
| |
| /* |
| * Reached the top - use headLIR as the dependent marker as all labels |
| * are barriers. |
| */ |
| if (stopHere == false && nextSlot < MAX_HOIST_DISTANCE) { |
| prevInstList[nextSlot++] = headLIR; |
| } |
| |
| /* |
| * At least one independent instruction is found. Scan in the reversed |
| * direction to find a beneficial slot. |
| */ |
| if (nextSlot >= 2) { |
| int firstSlot = nextSlot - 2; |
| int slot; |
| ArmLIR* depLIR = prevInstList[nextSlot-1]; |
| /* If there is ld-ld dependency, wait LDLD_DISTANCE cycles */ |
| if (!isPseudoOpcode(depLIR->opcode) && |
| (EncodingMap[depLIR->opcode].flags & IS_LOAD)) { |
| firstSlot -= LDLD_DISTANCE; |
| } |
| /* |
| * Make sure we check slot >= 0 since firstSlot may be negative |
| * when the loop is first entered. |
| */ |
| for (slot = firstSlot; slot >= 0; slot--) { |
| ArmLIR* curLIR = prevInstList[slot]; |
| ArmLIR* prevLIR = prevInstList[slot+1]; |
| |
| /* Check the highest instruction */ |
| if (prevLIR->defMask == ENCODE_ALL) { |
| /* |
| * If the first instruction is a load, don't hoist anything |
| * above it since it is unlikely to be beneficial. |
| */ |
| if (EncodingMap[curLIR->opcode].flags & IS_LOAD) continue; |
| /* |
| * If the remaining number of slots is less than LD_LATENCY, |
| * insert the hoisted load here. |
| */ |
| if (slot < LD_LATENCY) break; |
| } |
| |
| /* |
| * NOTE: now prevLIR is guaranteed to be a non-pseudo |
| * instruction (ie accessing EncodingMap[prevLIR->opcode] is |
| * safe). |
| * |
| * Try to find two instructions with load/use dependency until |
| * the remaining instructions are less than LD_LATENCY. |
| */ |
| if (((curLIR->useMask & prevLIR->defMask) && |
| (EncodingMap[prevLIR->opcode].flags & IS_LOAD)) || |
| (slot < LD_LATENCY)) { |
| break; |
| } |
| } |
| |
| /* Found a slot to hoist to */ |
| if (slot >= 0) { |
| ArmLIR* curLIR = prevInstList[slot]; |
| ArmLIR* newLoadLIR = (ArmLIR* ) oatNew(sizeof(ArmLIR), |
| true, kAllocLIR); |
| *newLoadLIR = *thisLIR; |
| /* |
| * Insertion is guaranteed to succeed since checkLIR |
| * is never the first LIR on the list |
| */ |
| oatInsertLIRBefore((LIR*) curLIR, (LIR*) newLoadLIR); |
| thisLIR->flags.isNop = true; |
| } |
| } |
| } |
| } |
| |
| void oatApplyLocalOptimizations(CompilationUnit* cUnit, LIR* headLIR, |
| LIR* tailLIR) |
| { |
| if (!(cUnit->disableOpt & (1 << kLoadStoreElimination))) { |
| applyLoadStoreElimination(cUnit, (ArmLIR* ) headLIR, |
| (ArmLIR* ) tailLIR); |
| } |
| if (!(cUnit->disableOpt & (1 << kLoadHoisting))) { |
| applyLoadHoisting(cUnit, (ArmLIR* ) headLIR, (ArmLIR* ) tailLIR); |
| } |
| } |
| |
| } // namespace art |
