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-rw-r--r--src/compiler/codegen/LocalOptimizations.cc448
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diff --git a/src/compiler/codegen/LocalOptimizations.cc b/src/compiler/codegen/LocalOptimizations.cc
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+/*
+ * 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.
+ */
+
+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(TGT_LIR* lir1, TGT_LIR* 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, TGT_LIR* origLIR,
+ int dest, int src)
+{
+ /* Insert a move to replace the load */
+ TGT_LIR* 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,
+ TGT_LIR* headLIR,
+ TGT_LIR* tailLIR)
+{
+ TGT_LIR* 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;
+ TGT_LIR* 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) {
+ TGT_LIR* newStoreLIR =
+ (TGT_LIR* ) oatNew(cUnit, sizeof(TGT_LIR), 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,
+ TGT_LIR* headLIR,
+ TGT_LIR* tailLIR)
+{
+ TGT_LIR* thisLIR, *checkLIR;
+ /*
+ * Store the list of independent instructions that can be hoisted past.
+ * Will decide the best place to insert later.
+ */
+ TGT_LIR* 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;
+ TGT_LIR* 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--) {
+ TGT_LIR* curLIR = prevInstList[slot];
+ TGT_LIR* 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) {
+ TGT_LIR* curLIR = prevInstList[slot];
+ TGT_LIR* newLoadLIR = (TGT_LIR* ) oatNew(cUnit, sizeof(TGT_LIR),
+ 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, (TGT_LIR* ) headLIR,
+ (TGT_LIR* ) tailLIR);
+ }
+ if (!(cUnit->disableOpt & (1 << kLoadHoisting))) {
+ applyLoadHoisting(cUnit, (TGT_LIR* ) headLIR, (TGT_LIR* ) tailLIR);
+ }
+}
+
+} // namespace art
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