compiler/dex/quick/arm/call_arm.cc - platform/art - Gitiles

 /*
  * 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.
  */

 /* This file contains codegen for the Thumb2 ISA. */

 #include "arm_lir.h"
 #include "codegen_arm.h"
 #include "dex/quick/mir_to_lir-inl.h"
 #include "entrypoints/quick/quick_entrypoints.h"

 namespace art {

 /*
  * The sparse table in the literal pool is an array of <key,displacement>
  * pairs.  For each set, we'll load them as a pair using ldmia.
  * This means that the register number of the temp we use for the key
  * must be lower than the reg for the displacement.
  *
  * The test loop will look something like:
  *
  *   adr   r_base, <table>
  *   ldr   r_val, [rARM_SP, v_reg_off]
  *   mov   r_idx, #table_size
  * lp:
  *   ldmia r_base!, {r_key, r_disp}
  *   sub   r_idx, #1
  *   cmp   r_val, r_key
  *   ifeq
  *   add   rARM_PC, r_disp   ; This is the branch from which we compute displacement
  *   cbnz  r_idx, lp
  */
 void ArmMir2Lir::GenSparseSwitch(MIR* mir, uint32_t table_offset,
                                  RegLocation rl_src) {
   const uint16_t* table = cu_->insns + current_dalvik_offset_ + table_offset;
   if (cu_->verbose) {
     DumpSparseSwitchTable(table);
   }
   // Add the table to the list - we'll process it later
   SwitchTable *tab_rec =
       static_cast<SwitchTable*>(arena_->Alloc(sizeof(SwitchTable), kArenaAllocData));
   tab_rec->table = table;
   tab_rec->vaddr = current_dalvik_offset_;
   uint32_t size = table[1];
   tab_rec->targets = static_cast<LIR**>(arena_->Alloc(size * sizeof(LIR*), kArenaAllocLIR));
   switch_tables_.Insert(tab_rec);

   // Get the switch value
   rl_src = LoadValue(rl_src, kCoreReg);
   RegStorage r_base = AllocTemp();
   /* Allocate key and disp temps */
   RegStorage r_key = AllocTemp();
   RegStorage r_disp = AllocTemp();
   // Make sure r_key's register number is less than r_disp's number for ldmia
   if (r_key.GetReg() > r_disp.GetReg()) {
     RegStorage tmp = r_disp;
     r_disp = r_key;
     r_key = tmp;
   }
   // Materialize a pointer to the switch table
   NewLIR3(kThumb2Adr, r_base.GetReg(), 0, WrapPointer(tab_rec));
   // Set up r_idx
   RegStorage r_idx = AllocTemp();
   LoadConstant(r_idx, size);
   // Establish loop branch target
   LIR* target = NewLIR0(kPseudoTargetLabel);
   // Load next key/disp
   NewLIR2(kThumb2LdmiaWB, r_base.GetReg(), (1 << r_key.GetRegNum()) | (1 << r_disp.GetRegNum()));
   OpRegReg(kOpCmp, r_key, rl_src.reg);
   // Go if match. NOTE: No instruction set switch here - must stay Thumb2
   LIR* it = OpIT(kCondEq, "");
   LIR* switch_branch = NewLIR1(kThumb2AddPCR, r_disp.GetReg());
   OpEndIT(it);
   tab_rec->anchor = switch_branch;
   // Needs to use setflags encoding here
   OpRegRegImm(kOpSub, r_idx, r_idx, 1);  // For value == 1, this should set flags.
   DCHECK(last_lir_insn_->u.m.def_mask & ENCODE_CCODE);
   OpCondBranch(kCondNe, target);
 }


 void ArmMir2Lir::GenPackedSwitch(MIR* mir, uint32_t table_offset,
                                  RegLocation rl_src) {
   const uint16_t* table = cu_->insns + current_dalvik_offset_ + table_offset;
   if (cu_->verbose) {
     DumpPackedSwitchTable(table);
   }
   // Add the table to the list - we'll process it later
   SwitchTable *tab_rec =
       static_cast<SwitchTable*>(arena_->Alloc(sizeof(SwitchTable),  kArenaAllocData));
   tab_rec->table = table;
   tab_rec->vaddr = current_dalvik_offset_;
   uint32_t size = table[1];
   tab_rec->targets =
       static_cast<LIR**>(arena_->Alloc(size * sizeof(LIR*), kArenaAllocLIR));
   switch_tables_.Insert(tab_rec);

   // Get the switch value
   rl_src = LoadValue(rl_src, kCoreReg);
   RegStorage table_base = AllocTemp();
   // Materialize a pointer to the switch table
   NewLIR3(kThumb2Adr, table_base.GetReg(), 0, WrapPointer(tab_rec));
   int low_key = s4FromSwitchData(&table[2]);
   RegStorage keyReg;
   // Remove the bias, if necessary
   if (low_key == 0) {
     keyReg = rl_src.reg;
   } else {
     keyReg = AllocTemp();
     OpRegRegImm(kOpSub, keyReg, rl_src.reg, low_key);
   }
   // Bounds check - if < 0 or >= size continue following switch
   OpRegImm(kOpCmp, keyReg, size-1);
   LIR* branch_over = OpCondBranch(kCondHi, NULL);

   // Load the displacement from the switch table
   RegStorage disp_reg = AllocTemp();
   LoadBaseIndexed(table_base, keyReg, disp_reg, 2, k32);

   // ..and go! NOTE: No instruction set switch here - must stay Thumb2
   LIR* switch_branch = NewLIR1(kThumb2AddPCR, disp_reg.GetReg());
   tab_rec->anchor = switch_branch;

   /* branch_over target here */
   LIR* target = NewLIR0(kPseudoTargetLabel);
   branch_over->target = 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 ArmMir2Lir::GenFillArrayData(uint32_t table_offset, RegLocation rl_src) {
   const uint16_t* table = cu_->insns + current_dalvik_offset_ + table_offset;
   // Add the table to the list - we'll process it later
   FillArrayData *tab_rec =
       static_cast<FillArrayData*>(arena_->Alloc(sizeof(FillArrayData), kArenaAllocData));
   tab_rec->table = table;
   tab_rec->vaddr = current_dalvik_offset_;
   uint16_t width = tab_rec->table[1];
   uint32_t size = tab_rec->table[2] | ((static_cast<uint32_t>(tab_rec->table[3])) << 16);
   tab_rec->size = (size * width) + 8;

   fill_array_data_.Insert(tab_rec);

   // Making a call - use explicit registers
   FlushAllRegs();   /* Everything to home location */
   LoadValueDirectFixed(rl_src, rs_r0);
   LoadWordDisp(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pHandleFillArrayData).Int32Value(),
                rs_rARM_LR);
   // Materialize a pointer to the fill data image
   NewLIR3(kThumb2Adr, rs_r1.GetReg(), 0, WrapPointer(tab_rec));
   ClobberCallerSave();
   LIR* call_inst = OpReg(kOpBlx, rs_rARM_LR);
   MarkSafepointPC(call_inst);
 }

 /*
  * Handle unlocked -> thin locked transition inline or else call out to quick entrypoint. For more
  * details see monitor.cc.
  */
 void ArmMir2Lir::GenMonitorEnter(int opt_flags, RegLocation rl_src) {
   FlushAllRegs();
   // FIXME: need separate LoadValues for object references.
   LoadValueDirectFixed(rl_src, rs_r0);  // Get obj
   LockCallTemps();  // Prepare for explicit register usage
   constexpr bool kArchVariantHasGoodBranchPredictor = false;  // TODO: true if cortex-A15.
   if (kArchVariantHasGoodBranchPredictor) {
     LIR* null_check_branch = nullptr;
     if ((opt_flags & MIR_IGNORE_NULL_CHECK) && !(cu_->disable_opt & (1 << kNullCheckElimination))) {
       null_check_branch = nullptr;  // No null check.
     } else {
       // If the null-check fails its handled by the slow-path to reduce exception related meta-data.
       if (Runtime::Current()->ExplicitNullChecks()) {
         null_check_branch = OpCmpImmBranch(kCondEq, rs_r0, 0, NULL);
       }
     }
     Load32Disp(rs_rARM_SELF, Thread::ThinLockIdOffset<4>().Int32Value(), rs_r2);
     NewLIR3(kThumb2Ldrex, rs_r1.GetReg(), rs_r0.GetReg(),
         mirror::Object::MonitorOffset().Int32Value() >> 2);
     MarkPossibleNullPointerException(opt_flags);
     LIR* not_unlocked_branch = OpCmpImmBranch(kCondNe, rs_r1, 0, NULL);
     NewLIR4(kThumb2Strex, rs_r1.GetReg(), rs_r2.GetReg(), rs_r0.GetReg(),
         mirror::Object::MonitorOffset().Int32Value() >> 2);
     LIR* lock_success_branch = OpCmpImmBranch(kCondEq, rs_r1, 0, NULL);


     LIR* slow_path_target = NewLIR0(kPseudoTargetLabel);
     not_unlocked_branch->target = slow_path_target;
     if (null_check_branch != nullptr) {
       null_check_branch->target = slow_path_target;
     }
     // TODO: move to a slow path.
     // Go expensive route - artLockObjectFromCode(obj);
     LoadWordDisp(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pLockObject).Int32Value(), rs_rARM_LR);
     ClobberCallerSave();
     LIR* call_inst = OpReg(kOpBlx, rs_rARM_LR);
     MarkSafepointPC(call_inst);

     LIR* success_target = NewLIR0(kPseudoTargetLabel);
     lock_success_branch->target = success_target;
     GenMemBarrier(kLoadLoad);
   } else {
     // Explicit null-check as slow-path is entered using an IT.
     GenNullCheck(rs_r0, opt_flags);
     Load32Disp(rs_rARM_SELF, Thread::ThinLockIdOffset<4>().Int32Value(), rs_r2);
     NewLIR3(kThumb2Ldrex, rs_r1.GetReg(), rs_r0.GetReg(),
         mirror::Object::MonitorOffset().Int32Value() >> 2);
     MarkPossibleNullPointerException(opt_flags);
     OpRegImm(kOpCmp, rs_r1, 0);
     LIR* it = OpIT(kCondEq, "");
     NewLIR4(kThumb2Strex/*eq*/, rs_r1.GetReg(), rs_r2.GetReg(), rs_r0.GetReg(),
         mirror::Object::MonitorOffset().Int32Value() >> 2);
     OpEndIT(it);
     OpRegImm(kOpCmp, rs_r1, 0);
     it = OpIT(kCondNe, "T");
     // Go expensive route - artLockObjectFromCode(self, obj);
     LoadWordDisp/*ne*/(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pLockObject).Int32Value(),
                        rs_rARM_LR);
     ClobberCallerSave();
     LIR* call_inst = OpReg(kOpBlx/*ne*/, rs_rARM_LR);
     OpEndIT(it);
     MarkSafepointPC(call_inst);
     GenMemBarrier(kLoadLoad);
   }
 }

 /*
  * Handle thin locked -> unlocked transition inline or else call out to quick entrypoint. For more
  * details see monitor.cc. Note the code below doesn't use ldrex/strex as the code holds the lock
  * and can only give away ownership if its suspended.
  */
 void ArmMir2Lir::GenMonitorExit(int opt_flags, RegLocation rl_src) {
   FlushAllRegs();
   LoadValueDirectFixed(rl_src, rs_r0);  // Get obj
   LockCallTemps();  // Prepare for explicit register usage
   LIR* null_check_branch = nullptr;
   Load32Disp(rs_rARM_SELF, Thread::ThinLockIdOffset<4>().Int32Value(), rs_r2);
   constexpr bool kArchVariantHasGoodBranchPredictor = false;  // TODO: true if cortex-A15.
   if (kArchVariantHasGoodBranchPredictor) {
     if ((opt_flags & MIR_IGNORE_NULL_CHECK) && !(cu_->disable_opt & (1 << kNullCheckElimination))) {
       null_check_branch = nullptr;  // No null check.
     } else {
       // If the null-check fails its handled by the slow-path to reduce exception related meta-data.
       if (Runtime::Current()->ExplicitNullChecks()) {
         null_check_branch = OpCmpImmBranch(kCondEq, rs_r0, 0, NULL);
       }
     }
     Load32Disp(rs_r0, mirror::Object::MonitorOffset().Int32Value(), rs_r1);
     MarkPossibleNullPointerException(opt_flags);
     LoadConstantNoClobber(rs_r3, 0);
     LIR* slow_unlock_branch = OpCmpBranch(kCondNe, rs_r1, rs_r2, NULL);
     Store32Disp(rs_r0, mirror::Object::MonitorOffset().Int32Value(), rs_r3);
     LIR* unlock_success_branch = OpUnconditionalBranch(NULL);

     LIR* slow_path_target = NewLIR0(kPseudoTargetLabel);
     slow_unlock_branch->target = slow_path_target;
     if (null_check_branch != nullptr) {
       null_check_branch->target = slow_path_target;
     }
     // TODO: move to a slow path.
     // Go expensive route - artUnlockObjectFromCode(obj);
     LoadWordDisp(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pUnlockObject).Int32Value(), rs_rARM_LR);
     ClobberCallerSave();
     LIR* call_inst = OpReg(kOpBlx, rs_rARM_LR);
     MarkSafepointPC(call_inst);

     LIR* success_target = NewLIR0(kPseudoTargetLabel);
     unlock_success_branch->target = success_target;
     GenMemBarrier(kStoreLoad);
   } else {
     // Explicit null-check as slow-path is entered using an IT.
     GenNullCheck(rs_r0, opt_flags);
     Load32Disp(rs_r0, mirror::Object::MonitorOffset().Int32Value(), rs_r1);  // Get lock
     MarkPossibleNullPointerException(opt_flags);
     Load32Disp(rs_rARM_SELF, Thread::ThinLockIdOffset<4>().Int32Value(), rs_r2);
     LoadConstantNoClobber(rs_r3, 0);
     // Is lock unheld on lock or held by us (==thread_id) on unlock?
     OpRegReg(kOpCmp, rs_r1, rs_r2);
     LIR* it = OpIT(kCondEq, "EE");
     Store32Disp/*eq*/(rs_r0, mirror::Object::MonitorOffset().Int32Value(), rs_r3);
     // Go expensive route - UnlockObjectFromCode(obj);
     LoadWordDisp/*ne*/(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pUnlockObject).Int32Value(),
                        rs_rARM_LR);
     ClobberCallerSave();
     LIR* call_inst = OpReg(kOpBlx/*ne*/, rs_rARM_LR);
     OpEndIT(it);
     MarkSafepointPC(call_inst);
     GenMemBarrier(kStoreLoad);
   }
 }

 void ArmMir2Lir::GenMoveException(RegLocation rl_dest) {
   int ex_offset = Thread::ExceptionOffset<4>().Int32Value();
   RegLocation rl_result = EvalLoc(rl_dest, kCoreReg, true);
   RegStorage reset_reg = AllocTemp();
   Load32Disp(rs_rARM_SELF, ex_offset, rl_result.reg);
   LoadConstant(reset_reg, 0);
   Store32Disp(rs_rARM_SELF, ex_offset, reset_reg);
   FreeTemp(reset_reg);
   StoreValue(rl_dest, rl_result);
 }

 /*
  * Mark garbage collection card. Skip if the value we're storing is null.
  */
 void ArmMir2Lir::MarkGCCard(RegStorage val_reg, RegStorage tgt_addr_reg) {
   RegStorage reg_card_base = AllocTemp();
   RegStorage reg_card_no = AllocTemp();
   LIR* branch_over = OpCmpImmBranch(kCondEq, val_reg, 0, NULL);
   LoadWordDisp(rs_rARM_SELF, Thread::CardTableOffset<4>().Int32Value(), reg_card_base);
   OpRegRegImm(kOpLsr, reg_card_no, tgt_addr_reg, gc::accounting::CardTable::kCardShift);
   StoreBaseIndexed(reg_card_base, reg_card_no, reg_card_base, 0, kUnsignedByte);
   LIR* target = NewLIR0(kPseudoTargetLabel);
   branch_over->target = target;
   FreeTemp(reg_card_base);
   FreeTemp(reg_card_no);
 }

 void ArmMir2Lir::GenEntrySequence(RegLocation* ArgLocs, RegLocation rl_method) {
   int spill_count = num_core_spills_ + num_fp_spills_;
   /*
    * On entry, r0, r1, r2 & r3 are live.  Let the register allocation
    * mechanism know so it doesn't try to use any of them when
    * expanding the frame or flushing.  This leaves the utility
    * code with a single temp: r12.  This should be enough.
    */
   LockTemp(rs_r0);
   LockTemp(rs_r1);
   LockTemp(rs_r2);
   LockTemp(rs_r3);

   /*
    * We can safely skip the stack overflow check if we're
    * a leaf *and* our frame size < fudge factor.
    */
   bool skip_overflow_check = (mir_graph_->MethodIsLeaf() &&
                             (static_cast<size_t>(frame_size_) <
                             Thread::kStackOverflowReservedBytes));
   NewLIR0(kPseudoMethodEntry);
   if (!skip_overflow_check) {
     if (Runtime::Current()->ExplicitStackOverflowChecks()) {
       /* Load stack limit */
       Load32Disp(rs_rARM_SELF, Thread::StackEndOffset<4>().Int32Value(), rs_r12);
     }
   }
   /* Spill core callee saves */
   NewLIR1(kThumb2Push, core_spill_mask_);
   /* Need to spill any FP regs? */
   if (num_fp_spills_) {
     /*
      * NOTE: fp spills are a little different from core spills in that
      * they are pushed as a contiguous block.  When promoting from
      * the fp set, we must allocate all singles from s16..highest-promoted
      */
     NewLIR1(kThumb2VPushCS, num_fp_spills_);
   }

   const int spill_size = spill_count * 4;
   const int frame_size_without_spills = frame_size_ - spill_size;
   if (!skip_overflow_check) {
     if (Runtime::Current()->ExplicitStackOverflowChecks()) {
       class StackOverflowSlowPath : public LIRSlowPath {
        public:
         StackOverflowSlowPath(Mir2Lir* m2l, LIR* branch, bool restore_lr, size_t sp_displace)
             : LIRSlowPath(m2l, m2l->GetCurrentDexPc(), branch, nullptr), restore_lr_(restore_lr),
               sp_displace_(sp_displace) {
         }
         void Compile() OVERRIDE {
           m2l_->ResetRegPool();
           m2l_->ResetDefTracking();
           GenerateTargetLabel(kPseudoThrowTarget);
           if (restore_lr_) {
             m2l_->LoadWordDisp(rs_rARM_SP, sp_displace_ - 4, rs_rARM_LR);
           }
           m2l_->OpRegImm(kOpAdd, rs_rARM_SP, sp_displace_);
           m2l_->ClobberCallerSave();
           ThreadOffset<4> func_offset = QUICK_ENTRYPOINT_OFFSET(4, pThrowStackOverflow);
           // Load the entrypoint directly into the pc instead of doing a load + branch. Assumes
           // codegen and target are in thumb2 mode.
           // NOTE: native pointer.
           m2l_->LoadWordDisp(rs_rARM_SELF, func_offset.Int32Value(), rs_rARM_PC);
         }

        private:
         const bool restore_lr_;
         const size_t sp_displace_;
       };
       if (static_cast<size_t>(frame_size_) > Thread::kStackOverflowReservedUsableBytes) {
         OpRegRegImm(kOpSub, rs_rARM_LR, rs_rARM_SP, frame_size_without_spills);
         LIR* branch = OpCmpBranch(kCondUlt, rs_rARM_LR, rs_r12, nullptr);
         // Need to restore LR since we used it as a temp.
         AddSlowPath(new(arena_)StackOverflowSlowPath(this, branch, true, spill_size));
         OpRegCopy(rs_rARM_SP, rs_rARM_LR);     // Establish stack
       } else {
         // If the frame is small enough we are guaranteed to have enough space that remains to
         // handle signals on the user stack.
         OpRegRegImm(kOpSub, rs_rARM_SP, rs_rARM_SP, frame_size_without_spills);
         LIR* branch = OpCmpBranch(kCondUlt, rs_rARM_SP, rs_r12, nullptr);
         AddSlowPath(new(arena_)StackOverflowSlowPath(this, branch, false, frame_size_));
       }
     } else {
       // Implicit stack overflow check.
       // Generate a load from [sp, #-overflowsize].  If this is in the stack
       // redzone we will get a segmentation fault.
       //
       // Caveat coder: if someone changes the kStackOverflowReservedBytes value
       // we need to make sure that it's loadable in an immediate field of
       // a sub instruction.  Otherwise we will get a temp allocation and the
       // code size will increase.
       OpRegRegImm(kOpSub, rs_r12, rs_rARM_SP, Thread::kStackOverflowReservedBytes);
       Load32Disp(rs_r12, 0, rs_r12);
       MarkPossibleStackOverflowException();
       OpRegImm(kOpSub, rs_rARM_SP, frame_size_without_spills);
     }
   } else {
     OpRegImm(kOpSub, rs_rARM_SP, frame_size_without_spills);
   }

   FlushIns(ArgLocs, rl_method);

   FreeTemp(rs_r0);
   FreeTemp(rs_r1);
   FreeTemp(rs_r2);
   FreeTemp(rs_r3);
 }

 void ArmMir2Lir::GenExitSequence() {
   int spill_count = num_core_spills_ + num_fp_spills_;
   /*
    * In the exit path, r0/r1 are live - make sure they aren't
    * allocated by the register utilities as temps.
    */
   LockTemp(rs_r0);
   LockTemp(rs_r1);

   NewLIR0(kPseudoMethodExit);
   OpRegImm(kOpAdd, rs_rARM_SP, frame_size_ - (spill_count * 4));
   /* Need to restore any FP callee saves? */
   if (num_fp_spills_) {
     NewLIR1(kThumb2VPopCS, num_fp_spills_);
   }
   if (core_spill_mask_ & (1 << rs_rARM_LR.GetRegNum())) {
     /* Unspill rARM_LR to rARM_PC */
     core_spill_mask_ &= ~(1 << rs_rARM_LR.GetRegNum());
     core_spill_mask_ |= (1 << rs_rARM_PC.GetRegNum());
   }
   NewLIR1(kThumb2Pop, core_spill_mask_);
   if (!(core_spill_mask_ & (1 << rs_rARM_PC.GetRegNum()))) {
     /* We didn't pop to rARM_PC, so must do a bv rARM_LR */
     NewLIR1(kThumbBx, rs_rARM_LR.GetReg());
   }
 }

 void ArmMir2Lir::GenSpecialExitSequence() {
   NewLIR1(kThumbBx, rs_rARM_LR.GetReg());
 }

 }  // namespace art
	/*
	* 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.
	*/

	/* This file contains codegen for the Thumb2 ISA. */

	#include "arm_lir.h"
	#include "codegen_arm.h"
	#include "dex/quick/mir_to_lir-inl.h"
	#include "entrypoints/quick/quick_entrypoints.h"

	namespace art {

	/*
	* The sparse table in the literal pool is an array of <key,displacement>
	* pairs. For each set, we'll load them as a pair using ldmia.
	* This means that the register number of the temp we use for the key
	* must be lower than the reg for the displacement.
	*
	* The test loop will look something like:
	*
	* adr r_base, <table>
	* ldr r_val, [rARM_SP, v_reg_off]
	* mov r_idx, #table_size
	* lp:
	* ldmia r_base!, {r_key, r_disp}
	* sub r_idx, #1
	* cmp r_val, r_key
	* ifeq
	* add rARM_PC, r_disp ; This is the branch from which we compute displacement
	* cbnz r_idx, lp
	*/
	void ArmMir2Lir::GenSparseSwitch(MIR* mir, uint32_t table_offset,
	RegLocation rl_src) {
	const uint16_t* table = cu_->insns + current_dalvik_offset_ + table_offset;
	if (cu_->verbose) {
	DumpSparseSwitchTable(table);
	}
	// Add the table to the list - we'll process it later
	SwitchTable *tab_rec =
	static_cast<SwitchTable*>(arena_->Alloc(sizeof(SwitchTable), kArenaAllocData));
	tab_rec->table = table;
	tab_rec->vaddr = current_dalvik_offset_;
	uint32_t size = table[1];
	tab_rec->targets = static_cast<LIR*>(arena_->Alloc(size sizeof(LIR*), kArenaAllocLIR));
	switch_tables_.Insert(tab_rec);

	// Get the switch value
	rl_src = LoadValue(rl_src, kCoreReg);
	RegStorage r_base = AllocTemp();
	/* Allocate key and disp temps */
	RegStorage r_key = AllocTemp();
	RegStorage r_disp = AllocTemp();
	// Make sure r_key's register number is less than r_disp's number for ldmia
	if (r_key.GetReg() > r_disp.GetReg()) {
	RegStorage tmp = r_disp;
	r_disp = r_key;
	r_key = tmp;
	}
	// Materialize a pointer to the switch table
	NewLIR3(kThumb2Adr, r_base.GetReg(), 0, WrapPointer(tab_rec));
	// Set up r_idx
	RegStorage r_idx = AllocTemp();
	LoadConstant(r_idx, size);
	// Establish loop branch target
	LIR* target = NewLIR0(kPseudoTargetLabel);
	// Load next key/disp
	NewLIR2(kThumb2LdmiaWB, r_base.GetReg(), (1 << r_key.GetRegNum()) \| (1 << r_disp.GetRegNum()));
	OpRegReg(kOpCmp, r_key, rl_src.reg);
	// Go if match. NOTE: No instruction set switch here - must stay Thumb2
	LIR* it = OpIT(kCondEq, "");
	LIR* switch_branch = NewLIR1(kThumb2AddPCR, r_disp.GetReg());
	OpEndIT(it);
	tab_rec->anchor = switch_branch;
	// Needs to use setflags encoding here
	OpRegRegImm(kOpSub, r_idx, r_idx, 1); // For value == 1, this should set flags.
	DCHECK(last_lir_insn_->u.m.def_mask & ENCODE_CCODE);
	OpCondBranch(kCondNe, target);
	}


	void ArmMir2Lir::GenPackedSwitch(MIR* mir, uint32_t table_offset,
	RegLocation rl_src) {
	const uint16_t* table = cu_->insns + current_dalvik_offset_ + table_offset;
	if (cu_->verbose) {
	DumpPackedSwitchTable(table);
	}
	// Add the table to the list - we'll process it later
	SwitchTable *tab_rec =
	static_cast<SwitchTable*>(arena_->Alloc(sizeof(SwitchTable), kArenaAllocData));
	tab_rec->table = table;
	tab_rec->vaddr = current_dalvik_offset_;
	uint32_t size = table[1];
	tab_rec->targets =
	static_cast<LIR*>(arena_->Alloc(size sizeof(LIR*), kArenaAllocLIR));
	switch_tables_.Insert(tab_rec);

	// Get the switch value
	rl_src = LoadValue(rl_src, kCoreReg);
	RegStorage table_base = AllocTemp();
	// Materialize a pointer to the switch table
	NewLIR3(kThumb2Adr, table_base.GetReg(), 0, WrapPointer(tab_rec));
	int low_key = s4FromSwitchData(&table[2]);
	RegStorage keyReg;
	// Remove the bias, if necessary
	if (low_key == 0) {
	keyReg = rl_src.reg;
	} else {
	keyReg = AllocTemp();
	OpRegRegImm(kOpSub, keyReg, rl_src.reg, low_key);
	}
	// Bounds check - if < 0 or >= size continue following switch
	OpRegImm(kOpCmp, keyReg, size-1);
	LIR* branch_over = OpCondBranch(kCondHi, NULL);

	// Load the displacement from the switch table
	RegStorage disp_reg = AllocTemp();
	LoadBaseIndexed(table_base, keyReg, disp_reg, 2, k32);

	// ..and go! NOTE: No instruction set switch here - must stay Thumb2
	LIR* switch_branch = NewLIR1(kThumb2AddPCR, disp_reg.GetReg());
	tab_rec->anchor = switch_branch;

	/* branch_over target here */
	LIR* target = NewLIR0(kPseudoTargetLabel);
	branch_over->target = 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 ArmMir2Lir::GenFillArrayData(uint32_t table_offset, RegLocation rl_src) {
	const uint16_t* table = cu_->insns + current_dalvik_offset_ + table_offset;
	// Add the table to the list - we'll process it later
	FillArrayData *tab_rec =
	static_cast<FillArrayData*>(arena_->Alloc(sizeof(FillArrayData), kArenaAllocData));
	tab_rec->table = table;
	tab_rec->vaddr = current_dalvik_offset_;
	uint16_t width = tab_rec->table[1];
	uint32_t size = tab_rec->table[2] \| ((static_cast<uint32_t>(tab_rec->table[3])) << 16);
	tab_rec->size = (size * width) + 8;

	fill_array_data_.Insert(tab_rec);

	// Making a call - use explicit registers
	FlushAllRegs(); /* Everything to home location */
	LoadValueDirectFixed(rl_src, rs_r0);
	LoadWordDisp(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pHandleFillArrayData).Int32Value(),
	rs_rARM_LR);
	// Materialize a pointer to the fill data image
	NewLIR3(kThumb2Adr, rs_r1.GetReg(), 0, WrapPointer(tab_rec));
	ClobberCallerSave();
	LIR* call_inst = OpReg(kOpBlx, rs_rARM_LR);
	MarkSafepointPC(call_inst);
	}

	/*
	* Handle unlocked -> thin locked transition inline or else call out to quick entrypoint. For more
	* details see monitor.cc.
	*/
	void ArmMir2Lir::GenMonitorEnter(int opt_flags, RegLocation rl_src) {
	FlushAllRegs();
	// FIXME: need separate LoadValues for object references.
	LoadValueDirectFixed(rl_src, rs_r0); // Get obj
	LockCallTemps(); // Prepare for explicit register usage
	constexpr bool kArchVariantHasGoodBranchPredictor = false; // TODO: true if cortex-A15.
	if (kArchVariantHasGoodBranchPredictor) {
	LIR* null_check_branch = nullptr;
	if ((opt_flags & MIR_IGNORE_NULL_CHECK) && !(cu_->disable_opt & (1 << kNullCheckElimination))) {
	null_check_branch = nullptr; // No null check.
	} else {
	// If the null-check fails its handled by the slow-path to reduce exception related meta-data.
	if (Runtime::Current()->ExplicitNullChecks()) {
	null_check_branch = OpCmpImmBranch(kCondEq, rs_r0, 0, NULL);
	}
	}
	Load32Disp(rs_rARM_SELF, Thread::ThinLockIdOffset<4>().Int32Value(), rs_r2);
	NewLIR3(kThumb2Ldrex, rs_r1.GetReg(), rs_r0.GetReg(),
	mirror::Object::MonitorOffset().Int32Value() >> 2);
	MarkPossibleNullPointerException(opt_flags);
	LIR* not_unlocked_branch = OpCmpImmBranch(kCondNe, rs_r1, 0, NULL);
	NewLIR4(kThumb2Strex, rs_r1.GetReg(), rs_r2.GetReg(), rs_r0.GetReg(),
	mirror::Object::MonitorOffset().Int32Value() >> 2);
	LIR* lock_success_branch = OpCmpImmBranch(kCondEq, rs_r1, 0, NULL);


	LIR* slow_path_target = NewLIR0(kPseudoTargetLabel);
	not_unlocked_branch->target = slow_path_target;
	if (null_check_branch != nullptr) {
	null_check_branch->target = slow_path_target;
	}
	// TODO: move to a slow path.
	// Go expensive route - artLockObjectFromCode(obj);
	LoadWordDisp(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pLockObject).Int32Value(), rs_rARM_LR);
	ClobberCallerSave();
	LIR* call_inst = OpReg(kOpBlx, rs_rARM_LR);
	MarkSafepointPC(call_inst);

	LIR* success_target = NewLIR0(kPseudoTargetLabel);
	lock_success_branch->target = success_target;
	GenMemBarrier(kLoadLoad);
	} else {
	// Explicit null-check as slow-path is entered using an IT.
	GenNullCheck(rs_r0, opt_flags);
	Load32Disp(rs_rARM_SELF, Thread::ThinLockIdOffset<4>().Int32Value(), rs_r2);
	NewLIR3(kThumb2Ldrex, rs_r1.GetReg(), rs_r0.GetReg(),
	mirror::Object::MonitorOffset().Int32Value() >> 2);
	MarkPossibleNullPointerException(opt_flags);
	OpRegImm(kOpCmp, rs_r1, 0);
	LIR* it = OpIT(kCondEq, "");
	NewLIR4(kThumb2Strex/eq/, rs_r1.GetReg(), rs_r2.GetReg(), rs_r0.GetReg(),
	mirror::Object::MonitorOffset().Int32Value() >> 2);
	OpEndIT(it);
	OpRegImm(kOpCmp, rs_r1, 0);
	it = OpIT(kCondNe, "T");
	// Go expensive route - artLockObjectFromCode(self, obj);
	LoadWordDisp/ne/(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pLockObject).Int32Value(),
	rs_rARM_LR);
	ClobberCallerSave();
	LIR* call_inst = OpReg(kOpBlx/ne/, rs_rARM_LR);
	OpEndIT(it);
	MarkSafepointPC(call_inst);
	GenMemBarrier(kLoadLoad);
	}
	}

	/*
	* Handle thin locked -> unlocked transition inline or else call out to quick entrypoint. For more
	* details see monitor.cc. Note the code below doesn't use ldrex/strex as the code holds the lock
	* and can only give away ownership if its suspended.
	*/
	void ArmMir2Lir::GenMonitorExit(int opt_flags, RegLocation rl_src) {
	FlushAllRegs();
	LoadValueDirectFixed(rl_src, rs_r0); // Get obj
	LockCallTemps(); // Prepare for explicit register usage
	LIR* null_check_branch = nullptr;
	Load32Disp(rs_rARM_SELF, Thread::ThinLockIdOffset<4>().Int32Value(), rs_r2);
	constexpr bool kArchVariantHasGoodBranchPredictor = false; // TODO: true if cortex-A15.
	if (kArchVariantHasGoodBranchPredictor) {
	if ((opt_flags & MIR_IGNORE_NULL_CHECK) && !(cu_->disable_opt & (1 << kNullCheckElimination))) {
	null_check_branch = nullptr; // No null check.
	} else {
	// If the null-check fails its handled by the slow-path to reduce exception related meta-data.
	if (Runtime::Current()->ExplicitNullChecks()) {
	null_check_branch = OpCmpImmBranch(kCondEq, rs_r0, 0, NULL);
	}
	}
	Load32Disp(rs_r0, mirror::Object::MonitorOffset().Int32Value(), rs_r1);
	MarkPossibleNullPointerException(opt_flags);
	LoadConstantNoClobber(rs_r3, 0);
	LIR* slow_unlock_branch = OpCmpBranch(kCondNe, rs_r1, rs_r2, NULL);
	Store32Disp(rs_r0, mirror::Object::MonitorOffset().Int32Value(), rs_r3);
	LIR* unlock_success_branch = OpUnconditionalBranch(NULL);

	LIR* slow_path_target = NewLIR0(kPseudoTargetLabel);
	slow_unlock_branch->target = slow_path_target;
	if (null_check_branch != nullptr) {
	null_check_branch->target = slow_path_target;
	}
	// TODO: move to a slow path.
	// Go expensive route - artUnlockObjectFromCode(obj);
	LoadWordDisp(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pUnlockObject).Int32Value(), rs_rARM_LR);
	ClobberCallerSave();
	LIR* call_inst = OpReg(kOpBlx, rs_rARM_LR);
	MarkSafepointPC(call_inst);

	LIR* success_target = NewLIR0(kPseudoTargetLabel);
	unlock_success_branch->target = success_target;
	GenMemBarrier(kStoreLoad);
	} else {
	// Explicit null-check as slow-path is entered using an IT.
	GenNullCheck(rs_r0, opt_flags);
	Load32Disp(rs_r0, mirror::Object::MonitorOffset().Int32Value(), rs_r1); // Get lock
	MarkPossibleNullPointerException(opt_flags);
	Load32Disp(rs_rARM_SELF, Thread::ThinLockIdOffset<4>().Int32Value(), rs_r2);
	LoadConstantNoClobber(rs_r3, 0);
	// Is lock unheld on lock or held by us (==thread_id) on unlock?
	OpRegReg(kOpCmp, rs_r1, rs_r2);
	LIR* it = OpIT(kCondEq, "EE");
	Store32Disp/eq/(rs_r0, mirror::Object::MonitorOffset().Int32Value(), rs_r3);
	// Go expensive route - UnlockObjectFromCode(obj);
	LoadWordDisp/ne/(rs_rARM_SELF, QUICK_ENTRYPOINT_OFFSET(4, pUnlockObject).Int32Value(),
	rs_rARM_LR);
	ClobberCallerSave();
	LIR* call_inst = OpReg(kOpBlx/ne/, rs_rARM_LR);
	OpEndIT(it);
	MarkSafepointPC(call_inst);
	GenMemBarrier(kStoreLoad);
	}
	}

	void ArmMir2Lir::GenMoveException(RegLocation rl_dest) {
	int ex_offset = Thread::ExceptionOffset<4>().Int32Value();
	RegLocation rl_result = EvalLoc(rl_dest, kCoreReg, true);
	RegStorage reset_reg = AllocTemp();
	Load32Disp(rs_rARM_SELF, ex_offset, rl_result.reg);
	LoadConstant(reset_reg, 0);
	Store32Disp(rs_rARM_SELF, ex_offset, reset_reg);
	FreeTemp(reset_reg);
	StoreValue(rl_dest, rl_result);
	}

	/*
	* Mark garbage collection card. Skip if the value we're storing is null.
	*/
	void ArmMir2Lir::MarkGCCard(RegStorage val_reg, RegStorage tgt_addr_reg) {
	RegStorage reg_card_base = AllocTemp();
	RegStorage reg_card_no = AllocTemp();
	LIR* branch_over = OpCmpImmBranch(kCondEq, val_reg, 0, NULL);
	LoadWordDisp(rs_rARM_SELF, Thread::CardTableOffset<4>().Int32Value(), reg_card_base);
	OpRegRegImm(kOpLsr, reg_card_no, tgt_addr_reg, gc::accounting::CardTable::kCardShift);
	StoreBaseIndexed(reg_card_base, reg_card_no, reg_card_base, 0, kUnsignedByte);
	LIR* target = NewLIR0(kPseudoTargetLabel);
	branch_over->target = target;
	FreeTemp(reg_card_base);
	FreeTemp(reg_card_no);
	}

	void ArmMir2Lir::GenEntrySequence(RegLocation* ArgLocs, RegLocation rl_method) {
	int spill_count = num_core_spills_ + num_fp_spills_;
	/*
	* On entry, r0, r1, r2 & r3 are live. Let the register allocation
	* mechanism know so it doesn't try to use any of them when
	* expanding the frame or flushing. This leaves the utility
	* code with a single temp: r12. This should be enough.
	*/
	LockTemp(rs_r0);
	LockTemp(rs_r1);
	LockTemp(rs_r2);
	LockTemp(rs_r3);

	/*
	* We can safely skip the stack overflow check if we're
	* a leaf and our frame size < fudge factor.
	*/
	bool skip_overflow_check = (mir_graph_->MethodIsLeaf() &&
	(static_cast<size_t>(frame_size_) <
	Thread::kStackOverflowReservedBytes));
	NewLIR0(kPseudoMethodEntry);
	if (!skip_overflow_check) {
	if (Runtime::Current()->ExplicitStackOverflowChecks()) {
	/* Load stack limit */
	Load32Disp(rs_rARM_SELF, Thread::StackEndOffset<4>().Int32Value(), rs_r12);
	}
	}
	/* Spill core callee saves */
	NewLIR1(kThumb2Push, core_spill_mask_);
	/* Need to spill any FP regs? */
	if (num_fp_spills_) {
	/*
	* NOTE: fp spills are a little different from core spills in that
	* they are pushed as a contiguous block. When promoting from
	* the fp set, we must allocate all singles from s16..highest-promoted
	*/
	NewLIR1(kThumb2VPushCS, num_fp_spills_);
	}

	const int spill_size = spill_count * 4;
	const int frame_size_without_spills = frame_size_ - spill_size;
	if (!skip_overflow_check) {
	if (Runtime::Current()->ExplicitStackOverflowChecks()) {
	class StackOverflowSlowPath : public LIRSlowPath {
	public:
	StackOverflowSlowPath(Mir2Lir* m2l, LIR* branch, bool restore_lr, size_t sp_displace)
	: LIRSlowPath(m2l, m2l->GetCurrentDexPc(), branch, nullptr), restore_lr_(restore_lr),
	sp_displace_(sp_displace) {
	}
	void Compile() OVERRIDE {
	m2l_->ResetRegPool();
	m2l_->ResetDefTracking();
	GenerateTargetLabel(kPseudoThrowTarget);
	if (restore_lr_) {
	m2l_->LoadWordDisp(rs_rARM_SP, sp_displace_ - 4, rs_rARM_LR);
	}
	m2l_->OpRegImm(kOpAdd, rs_rARM_SP, sp_displace_);
	m2l_->ClobberCallerSave();
	ThreadOffset<4> func_offset = QUICK_ENTRYPOINT_OFFSET(4, pThrowStackOverflow);
	// Load the entrypoint directly into the pc instead of doing a load + branch. Assumes
	// codegen and target are in thumb2 mode.
	// NOTE: native pointer.
	m2l_->LoadWordDisp(rs_rARM_SELF, func_offset.Int32Value(), rs_rARM_PC);
	}

	private:
	const bool restore_lr_;
	const size_t sp_displace_;
	};
	if (static_cast<size_t>(frame_size_) > Thread::kStackOverflowReservedUsableBytes) {
	OpRegRegImm(kOpSub, rs_rARM_LR, rs_rARM_SP, frame_size_without_spills);
	LIR* branch = OpCmpBranch(kCondUlt, rs_rARM_LR, rs_r12, nullptr);
	// Need to restore LR since we used it as a temp.
	AddSlowPath(new(arena_)StackOverflowSlowPath(this, branch, true, spill_size));
	OpRegCopy(rs_rARM_SP, rs_rARM_LR); // Establish stack
	} else {
	// If the frame is small enough we are guaranteed to have enough space that remains to
	// handle signals on the user stack.
	OpRegRegImm(kOpSub, rs_rARM_SP, rs_rARM_SP, frame_size_without_spills);
	LIR* branch = OpCmpBranch(kCondUlt, rs_rARM_SP, rs_r12, nullptr);
	AddSlowPath(new(arena_)StackOverflowSlowPath(this, branch, false, frame_size_));
	}
	} else {
	// Implicit stack overflow check.
	// Generate a load from [sp, #-overflowsize]. If this is in the stack
	// redzone we will get a segmentation fault.
	//
	// Caveat coder: if someone changes the kStackOverflowReservedBytes value
	// we need to make sure that it's loadable in an immediate field of
	// a sub instruction. Otherwise we will get a temp allocation and the
	// code size will increase.
	OpRegRegImm(kOpSub, rs_r12, rs_rARM_SP, Thread::kStackOverflowReservedBytes);
	Load32Disp(rs_r12, 0, rs_r12);
	MarkPossibleStackOverflowException();
	OpRegImm(kOpSub, rs_rARM_SP, frame_size_without_spills);
	}
	} else {
	OpRegImm(kOpSub, rs_rARM_SP, frame_size_without_spills);
	}

	FlushIns(ArgLocs, rl_method);

	FreeTemp(rs_r0);
	FreeTemp(rs_r1);
	FreeTemp(rs_r2);
	FreeTemp(rs_r3);
	}

	void ArmMir2Lir::GenExitSequence() {
	int spill_count = num_core_spills_ + num_fp_spills_;
	/*
	* In the exit path, r0/r1 are live - make sure they aren't
	* allocated by the register utilities as temps.
	*/
	LockTemp(rs_r0);
	LockTemp(rs_r1);

	NewLIR0(kPseudoMethodExit);
	OpRegImm(kOpAdd, rs_rARM_SP, frame_size_ - (spill_count * 4));
	/* Need to restore any FP callee saves? */
	if (num_fp_spills_) {
	NewLIR1(kThumb2VPopCS, num_fp_spills_);
	}
	if (core_spill_mask_ & (1 << rs_rARM_LR.GetRegNum())) {
	/* Unspill rARM_LR to rARM_PC */
	core_spill_mask_ &= ~(1 << rs_rARM_LR.GetRegNum());
	core_spill_mask_ \|= (1 << rs_rARM_PC.GetRegNum());
	}
	NewLIR1(kThumb2Pop, core_spill_mask_);
	if (!(core_spill_mask_ & (1 << rs_rARM_PC.GetRegNum()))) {
	/* We didn't pop to rARM_PC, so must do a bv rARM_LR */
	NewLIR1(kThumbBx, rs_rARM_LR.GetReg());
	}
	}

	void ArmMir2Lir::GenSpecialExitSequence() {
	NewLIR1(kThumbBx, rs_rARM_LR.GetReg());
	}

	} // namespace art