/*
* 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 "compiler_internals.h"
#include "local_value_numbering.h"
#include "dataflow_iterator-inl.h"
namespace art {
static unsigned int Predecessors(BasicBlock* bb) {
return bb->predecessors->Size();
}
/* Setup a constant value for opcodes thare have the DF_SETS_CONST attribute */
void MIRGraph::SetConstant(int32_t ssa_reg, int value) {
is_constant_v_->SetBit(ssa_reg);
constant_values_[ssa_reg] = value;
}
void MIRGraph::SetConstantWide(int ssa_reg, int64_t value) {
is_constant_v_->SetBit(ssa_reg);
constant_values_[ssa_reg] = Low32Bits(value);
constant_values_[ssa_reg + 1] = High32Bits(value);
}
void MIRGraph::DoConstantPropogation(BasicBlock* bb) {
MIR* mir;
for (mir = bb->first_mir_insn; mir != NULL; mir = mir->next) {
int df_attributes = oat_data_flow_attributes_[mir->dalvikInsn.opcode];
DecodedInstruction *d_insn = &mir->dalvikInsn;
if (!(df_attributes & DF_HAS_DEFS)) continue;
/* Handle instructions that set up constants directly */
if (df_attributes & DF_SETS_CONST) {
if (df_attributes & DF_DA) {
int32_t vB = static_cast<int32_t>(d_insn->vB);
switch (d_insn->opcode) {
case Instruction::CONST_4:
case Instruction::CONST_16:
case Instruction::CONST:
SetConstant(mir->ssa_rep->defs[0], vB);
break;
case Instruction::CONST_HIGH16:
SetConstant(mir->ssa_rep->defs[0], vB << 16);
break;
case Instruction::CONST_WIDE_16:
case Instruction::CONST_WIDE_32:
SetConstantWide(mir->ssa_rep->defs[0], static_cast<int64_t>(vB));
break;
case Instruction::CONST_WIDE:
SetConstantWide(mir->ssa_rep->defs[0], d_insn->vB_wide);
break;
case Instruction::CONST_WIDE_HIGH16:
SetConstantWide(mir->ssa_rep->defs[0], static_cast<int64_t>(vB) << 48);
break;
default:
break;
}
}
/* Handle instructions that set up constants directly */
} else if (df_attributes & DF_IS_MOVE) {
int i;
for (i = 0; i < mir->ssa_rep->num_uses; i++) {
if (!is_constant_v_->IsBitSet(mir->ssa_rep->uses[i])) break;
}
/* Move a register holding a constant to another register */
if (i == mir->ssa_rep->num_uses) {
SetConstant(mir->ssa_rep->defs[0], constant_values_[mir->ssa_rep->uses[0]]);
if (df_attributes & DF_A_WIDE) {
SetConstant(mir->ssa_rep->defs[1], constant_values_[mir->ssa_rep->uses[1]]);
}
}
}
}
/* TODO: implement code to handle arithmetic operations */
}
void MIRGraph::PropagateConstants() {
is_constant_v_ = new (arena_) ArenaBitVector(arena_, GetNumSSARegs(), false);
constant_values_ = static_cast<int*>(arena_->Alloc(sizeof(int) * GetNumSSARegs(),
ArenaAllocator::kAllocDFInfo));
AllNodesIterator iter(this, false /* not iterative */);
for (BasicBlock* bb = iter.Next(); bb != NULL; bb = iter.Next()) {
DoConstantPropogation(bb);
}
}
/* Advance to next strictly dominated MIR node in an extended basic block */
static MIR* AdvanceMIR(BasicBlock** p_bb, MIR* mir) {
BasicBlock* bb = *p_bb;
if (mir != NULL) {
mir = mir->next;
if (mir == NULL) {
bb = bb->fall_through;
if ((bb == NULL) || Predecessors(bb) != 1) {
mir = NULL;
} else {
*p_bb = bb;
mir = bb->first_mir_insn;
}
}
}
return mir;
}
/*
* To be used at an invoke mir. If the logically next mir node represents
* a move-result, return it. Else, return NULL. If a move-result exists,
* it is required to immediately follow the invoke with no intervening
* opcodes or incoming arcs. However, if the result of the invoke is not
* used, a move-result may not be present.
*/
MIR* MIRGraph::FindMoveResult(BasicBlock* bb, MIR* mir) {
BasicBlock* tbb = bb;
mir = AdvanceMIR(&tbb, mir);
while (mir != NULL) {
int opcode = mir->dalvikInsn.opcode;
if ((mir->dalvikInsn.opcode == Instruction::MOVE_RESULT) ||
(mir->dalvikInsn.opcode == Instruction::MOVE_RESULT_OBJECT) ||
(mir->dalvikInsn.opcode == Instruction::MOVE_RESULT_WIDE)) {
break;
}
// Keep going if pseudo op, otherwise terminate
if (opcode < kNumPackedOpcodes) {
mir = NULL;
} else {
mir = AdvanceMIR(&tbb, mir);
}
}
return mir;
}
static BasicBlock* NextDominatedBlock(BasicBlock* bb) {
if (bb->block_type == kDead) {
return NULL;
}
DCHECK((bb->block_type == kEntryBlock) || (bb->block_type == kDalvikByteCode)
|| (bb->block_type == kExitBlock));
if (((bb->taken != NULL) && (bb->fall_through == NULL)) &&
((bb->taken->block_type == kDalvikByteCode) || (bb->taken->block_type == kExitBlock))) {
// Follow simple unconditional branches.
bb = bb->taken;
} else {
// Follow simple fallthrough
bb = (bb->taken != NULL) ? NULL : bb->fall_through;
}
if (bb == NULL || (Predecessors(bb) != 1)) {
return NULL;
}
DCHECK((bb->block_type == kDalvikByteCode) || (bb->block_type == kExitBlock));
return bb;
}
static MIR* FindPhi(BasicBlock* bb, int ssa_name) {
for (MIR* mir = bb->first_mir_insn; mir != NULL; mir = mir->next) {
if (static_cast<int>(mir->dalvikInsn.opcode) == kMirOpPhi) {
for (int i = 0; i < mir->ssa_rep->num_uses; i++) {
if (mir->ssa_rep->uses[i] == ssa_name) {
return mir;
}
}
}
}
return NULL;
}
static SelectInstructionKind SelectKind(MIR* mir) {
switch (mir->dalvikInsn.opcode) {
case Instruction::MOVE:
case Instruction::MOVE_OBJECT:
case Instruction::MOVE_16:
case Instruction::MOVE_OBJECT_16:
case Instruction::MOVE_FROM16:
case Instruction::MOVE_OBJECT_FROM16:
return kSelectMove;
case Instruction::CONST:
case Instruction::CONST_4:
case Instruction::CONST_16:
return kSelectConst;
case Instruction::GOTO:
case Instruction::GOTO_16:
case Instruction::GOTO_32:
return kSelectGoto;
default:
return kSelectNone;
}
}
int MIRGraph::GetSSAUseCount(int s_reg) {
return raw_use_counts_.Get(s_reg);
}
/* Do some MIR-level extended basic block optimizations */
bool MIRGraph::BasicBlockOpt(BasicBlock* bb) {
if (bb->block_type == kDead) {
return true;
}
int num_temps = 0;
LocalValueNumbering local_valnum(cu_);
while (bb != NULL) {
for (MIR* mir = bb->first_mir_insn; mir != NULL; mir = mir->next) {
// TUNING: use the returned value number for CSE.
local_valnum.GetValueNumber(mir);
// Look for interesting opcodes, skip otherwise
Instruction::Code opcode = mir->dalvikInsn.opcode;
switch (opcode) {
case Instruction::CMPL_FLOAT:
case Instruction::CMPL_DOUBLE:
case Instruction::CMPG_FLOAT:
case Instruction::CMPG_DOUBLE:
case Instruction::CMP_LONG:
if ((cu_->disable_opt & (1 << kBranchFusing)) != 0) {
// Bitcode doesn't allow this optimization.
break;
}
if (mir->next != NULL) {
MIR* mir_next = mir->next;
Instruction::Code br_opcode = mir_next->dalvikInsn.opcode;
ConditionCode ccode = kCondNv;
switch (br_opcode) {
case Instruction::IF_EQZ:
ccode = kCondEq;
break;
case Instruction::IF_NEZ:
ccode = kCondNe;
break;
case Instruction::IF_LTZ:
ccode = kCondLt;
break;
case Instruction::IF_GEZ:
ccode = kCondGe;
break;
case Instruction::IF_GTZ:
ccode = kCondGt;
break;
case Instruction::IF_LEZ:
ccode = kCondLe;
break;
default:
break;
}
// Make sure result of cmp is used by next insn and nowhere else
if ((ccode != kCondNv) &&
(mir->ssa_rep->defs[0] == mir_next->ssa_rep->uses[0]) &&
(GetSSAUseCount(mir->ssa_rep->defs[0]) == 1)) {
mir_next->dalvikInsn.arg[0] = ccode;
switch (opcode) {
case Instruction::CMPL_FLOAT:
mir_next->dalvikInsn.opcode =
static_cast<Instruction::Code>(kMirOpFusedCmplFloat);
break;
case Instruction::CMPL_DOUBLE:
mir_next->dalvikInsn.opcode =
static_cast<Instruction::Code>(kMirOpFusedCmplDouble);
break;
case Instruction::CMPG_FLOAT:
mir_next->dalvikInsn.opcode =
static_cast<Instruction::Code>(kMirOpFusedCmpgFloat);
break;
case Instruction::CMPG_DOUBLE:
mir_next->dalvikInsn.opcode =
static_cast<Instruction::Code>(kMirOpFusedCmpgDouble);
break;
case Instruction::CMP_LONG:
mir_next->dalvikInsn.opcode =
static_cast<Instruction::Code>(kMirOpFusedCmpLong);
break;
default: LOG(ERROR) << "Unexpected opcode: " << opcode;
}
mir->dalvikInsn.opcode = static_cast<Instruction::Code>(kMirOpNop);
mir_next->ssa_rep->num_uses = mir->ssa_rep->num_uses;
mir_next->ssa_rep->uses = mir->ssa_rep->uses;
mir_next->ssa_rep->fp_use = mir->ssa_rep->fp_use;
mir_next->ssa_rep->num_defs = 0;
mir->ssa_rep->num_uses = 0;
mir->ssa_rep->num_defs = 0;
}
}
break;
case Instruction::GOTO:
case Instruction::GOTO_16:
case Instruction::GOTO_32:
case Instruction::IF_EQ:
case Instruction::IF_NE:
case Instruction::IF_LT:
case Instruction::IF_GE:
case Instruction::IF_GT:
case Instruction::IF_LE:
case Instruction::IF_EQZ:
case Instruction::IF_NEZ:
case Instruction::IF_LTZ:
case Instruction::IF_GEZ:
case Instruction::IF_GTZ:
case Instruction::IF_LEZ:
// If we've got a backwards branch to return, no need to suspend check.
if ((IsBackedge(bb, bb->taken) && bb->taken->dominates_return) ||
(IsBackedge(bb, bb->fall_through) && bb->fall_through->dominates_return)) {
mir->optimization_flags |= MIR_IGNORE_SUSPEND_CHECK;
if (cu_->verbose) {
LOG(INFO) << "Suppressed suspend check on branch to return at 0x" << std::hex << mir->offset;
}
}
break;
default:
break;
}
// Is this the select pattern?
// TODO: flesh out support for Mips and X86. NOTE: llvm's select op doesn't quite work here.
// TUNING: expand to support IF_xx compare & branches
if (!(cu_->compiler_backend == kPortable) && (cu_->instruction_set == kThumb2) &&
((mir->dalvikInsn.opcode == Instruction::IF_EQZ) ||
(mir->dalvikInsn.opcode == Instruction::IF_NEZ))) {
BasicBlock* ft = bb->fall_through;
DCHECK(ft != NULL);
BasicBlock* ft_ft = ft->fall_through;
BasicBlock* ft_tk = ft->taken;
BasicBlock* tk = bb->taken;
DCHECK(tk != NULL);
BasicBlock* tk_ft = tk->fall_through;
BasicBlock* tk_tk = tk->taken;
/*
* In the select pattern, the taken edge goes to a block that unconditionally
* transfers to the rejoin block and the fall_though edge goes to a block that
* unconditionally falls through to the rejoin block.
*/
if ((tk_ft == NULL) && (ft_tk == NULL) && (tk_tk == ft_ft) &&
(Predecessors(tk) == 1) && (Predecessors(ft) == 1)) {
/*
* Okay - we have the basic diamond shape. At the very least, we can eliminate the
* suspend check on the taken-taken branch back to the join point.
*/
if (SelectKind(tk->last_mir_insn) == kSelectGoto) {
tk->last_mir_insn->optimization_flags |= (MIR_IGNORE_SUSPEND_CHECK);
}
// Are the block bodies something we can handle?
if ((ft->first_mir_insn == ft->last_mir_insn) &&
(tk->first_mir_insn != tk->last_mir_insn) &&
(tk->first_mir_insn->next == tk->last_mir_insn) &&
((SelectKind(ft->first_mir_insn) == kSelectMove) ||
(SelectKind(ft->first_mir_insn) == kSelectConst)) &&
(SelectKind(ft->first_mir_insn) == SelectKind(tk->first_mir_insn)) &&
(SelectKind(tk->last_mir_insn) == kSelectGoto)) {
// Almost there. Are the instructions targeting the same vreg?
MIR* if_true = tk->first_mir_insn;
MIR* if_false = ft->first_mir_insn;
// It's possible that the target of the select isn't used - skip those (rare) cases.
MIR* phi = FindPhi(tk_tk, if_true->ssa_rep->defs[0]);
if ((phi != NULL) && (if_true->dalvikInsn.vA == if_false->dalvikInsn.vA)) {
/*
* We'll convert the IF_EQZ/IF_NEZ to a SELECT. We need to find the
* Phi node in the merge block and delete it (while using the SSA name
* of the merge as the target of the SELECT. Delete both taken and
* fallthrough blocks, and set fallthrough to merge block.
* NOTE: not updating other dataflow info (no longer used at this point).
* If this changes, need to update i_dom, etc. here (and in CombineBlocks).
*/
if (opcode == Instruction::IF_NEZ) {
// Normalize.
MIR* tmp_mir = if_true;
if_true = if_false;
if_false = tmp_mir;
}
mir->dalvikInsn.opcode = static_cast<Instruction::Code>(kMirOpSelect);
bool const_form = (SelectKind(if_true) == kSelectConst);
if ((SelectKind(if_true) == kSelectMove)) {
if (IsConst(if_true->ssa_rep->uses[0]) &&
IsConst(if_false->ssa_rep->uses[0])) {
const_form = true;
if_true->dalvikInsn.vB = ConstantValue(if_true->ssa_rep->uses[0]);
if_false->dalvikInsn.vB = ConstantValue(if_false->ssa_rep->uses[0]);
}
}
if (const_form) {
// "true" set val in vB
mir->dalvikInsn.vB = if_true->dalvikInsn.vB;
// "false" set val in vC
mir->dalvikInsn.vC = if_false->dalvikInsn.vB;
} else {
DCHECK_EQ(SelectKind(if_true), kSelectMove);
DCHECK_EQ(SelectKind(if_false), kSelectMove);
int* src_ssa =
static_cast<int*>(arena_->Alloc(sizeof(int) * 3, ArenaAllocator::kAllocDFInfo));
src_ssa[0] = mir->ssa_rep->uses[0];
src_ssa[1] = if_true->ssa_rep->uses[0];
src_ssa[2] = if_false->ssa_rep->uses[0];
mir->ssa_rep->uses = src_ssa;
mir->ssa_rep->num_uses = 3;
}
mir->ssa_rep->num_defs = 1;
mir->ssa_rep->defs =
static_cast<int*>(arena_->Alloc(sizeof(int) * 1, ArenaAllocator::kAllocDFInfo));
mir->ssa_rep->fp_def =
static_cast<bool*>(arena_->Alloc(sizeof(bool) * 1, ArenaAllocator::kAllocDFInfo));
mir->ssa_rep->fp_def[0] = if_true->ssa_rep->fp_def[0];
// Match type of uses to def.
mir->ssa_rep->fp_use =
static_cast<bool*>(arena_->Alloc(sizeof(bool) * mir->ssa_rep->num_uses,
ArenaAllocator::kAllocDFInfo));
for (int i = 0; i < mir->ssa_rep->num_uses; i++) {
mir->ssa_rep->fp_use[i] = mir->ssa_rep->fp_def[0];
}
/*
* There is usually a Phi node in the join block for our two cases. If the
* Phi node only contains our two cases as input, we will use the result
* SSA name of the Phi node as our select result and delete the Phi. If
* the Phi node has more than two operands, we will arbitrarily use the SSA
* name of the "true" path, delete the SSA name of the "false" path from the
* Phi node (and fix up the incoming arc list).
*/
if (phi->ssa_rep->num_uses == 2) {
mir->ssa_rep->defs[0] = phi->ssa_rep->defs[0];
phi->dalvikInsn.opcode = static_cast<Instruction::Code>(kMirOpNop);
} else {
int dead_def = if_false->ssa_rep->defs[0];
int live_def = if_true->ssa_rep->defs[0];
mir->ssa_rep->defs[0] = live_def;
int* incoming = reinterpret_cast<int*>(phi->dalvikInsn.vB);
for (int i = 0; i < phi->ssa_rep->num_uses; i++) {
if (phi->ssa_rep->uses[i] == live_def) {
incoming[i] = bb->id;
}
}
for (int i = 0; i < phi->ssa_rep->num_uses; i++) {
if (phi->ssa_rep->uses[i] == dead_def) {
int last_slot = phi->ssa_rep->num_uses - 1;
phi->ssa_rep->uses[i] = phi->ssa_rep->uses[last_slot];
incoming[i] = incoming[last_slot];
}
}
}
phi->ssa_rep->num_uses--;
bb->taken = NULL;
tk->block_type = kDead;
for (MIR* tmir = ft->first_mir_insn; tmir != NULL; tmir = tmir->next) {
tmir->dalvikInsn.opcode = static_cast<Instruction::Code>(kMirOpNop);
}
}
}
}
}
}
bb = NextDominatedBlock(bb);
}
if (num_temps > cu_->num_compiler_temps) {
cu_->num_compiler_temps = num_temps;
}
return true;
}
void MIRGraph::NullCheckEliminationInit(struct BasicBlock* bb) {
if (bb->data_flow_info != NULL) {
bb->data_flow_info->ending_null_check_v =
new (arena_) ArenaBitVector(arena_, GetNumSSARegs(), false, kBitMapNullCheck);
}
}
/* Collect stats on number of checks removed */
void MIRGraph::CountChecks(struct BasicBlock* bb) {
if (bb->data_flow_info != NULL) {
for (MIR* mir = bb->first_mir_insn; mir != NULL; mir = mir->next) {
if (mir->ssa_rep == NULL) {
continue;
}
int df_attributes = oat_data_flow_attributes_[mir->dalvikInsn.opcode];
if (df_attributes & DF_HAS_NULL_CHKS) {
checkstats_->null_checks++;
if (mir->optimization_flags & MIR_IGNORE_NULL_CHECK) {
checkstats_->null_checks_eliminated++;
}
}
if (df_attributes & DF_HAS_RANGE_CHKS) {
checkstats_->range_checks++;
if (mir->optimization_flags & MIR_IGNORE_RANGE_CHECK) {
checkstats_->range_checks_eliminated++;
}
}
}
}
}
/* Try to make common case the fallthrough path */
static bool LayoutBlocks(struct BasicBlock* bb) {
// TODO: For now, just looking for direct throws. Consider generalizing for profile feedback
if (!bb->explicit_throw) {
return false;
}
BasicBlock* walker = bb;
while (true) {
// Check termination conditions
if ((walker->block_type == kEntryBlock) || (Predecessors(walker) != 1)) {
break;
}
BasicBlock* prev = walker->predecessors->Get(0);
if (prev->conditional_branch) {
if (prev->fall_through == walker) {
// Already done - return
break;
}
DCHECK_EQ(walker, prev->taken);
// Got one. Flip it and exit
Instruction::Code opcode = prev->last_mir_insn->dalvikInsn.opcode;
switch (opcode) {
case Instruction::IF_EQ: opcode = Instruction::IF_NE; break;
case Instruction::IF_NE: opcode = Instruction::IF_EQ; break;
case Instruction::IF_LT: opcode = Instruction::IF_GE; break;
case Instruction::IF_GE: opcode = Instruction::IF_LT; break;
case Instruction::IF_GT: opcode = Instruction::IF_LE; break;
case Instruction::IF_LE: opcode = Instruction::IF_GT; break;
case Instruction::IF_EQZ: opcode = Instruction::IF_NEZ; break;
case Instruction::IF_NEZ: opcode = Instruction::IF_EQZ; break;
case Instruction::IF_LTZ: opcode = Instruction::IF_GEZ; break;
case Instruction::IF_GEZ: opcode = Instruction::IF_LTZ; break;
case Instruction::IF_GTZ: opcode = Instruction::IF_LEZ; break;
case Instruction::IF_LEZ: opcode = Instruction::IF_GTZ; break;
default: LOG(FATAL) << "Unexpected opcode " << opcode;
}
prev->last_mir_insn->dalvikInsn.opcode = opcode;
BasicBlock* t_bb = prev->taken;
prev->taken = prev->fall_through;
prev->fall_through = t_bb;
break;
}
walker = prev;
}
return false;
}
/* Combine any basic blocks terminated by instructions that we now know can't throw */
bool MIRGraph::CombineBlocks(struct BasicBlock* bb) {
// Loop here to allow combining a sequence of blocks
while (true) {
// Check termination conditions
if ((bb->first_mir_insn == NULL)
|| (bb->data_flow_info == NULL)
|| (bb->block_type == kExceptionHandling)
|| (bb->block_type == kExitBlock)
|| (bb->block_type == kDead)
|| ((bb->taken == NULL) || (bb->taken->block_type != kExceptionHandling))
|| (bb->successor_block_list.block_list_type != kNotUsed)
|| (static_cast<int>(bb->last_mir_insn->dalvikInsn.opcode) != kMirOpCheck)) {
break;
}
// Test the kMirOpCheck instruction
MIR* mir = bb->last_mir_insn;
// Grab the attributes from the paired opcode
MIR* throw_insn = mir->meta.throw_insn;
int df_attributes = oat_data_flow_attributes_[throw_insn->dalvikInsn.opcode];
bool can_combine = true;
if (df_attributes & DF_HAS_NULL_CHKS) {
can_combine &= ((throw_insn->optimization_flags & MIR_IGNORE_NULL_CHECK) != 0);
}
if (df_attributes & DF_HAS_RANGE_CHKS) {
can_combine &= ((throw_insn->optimization_flags & MIR_IGNORE_RANGE_CHECK) != 0);
}
if (!can_combine) {
break;
}
// OK - got one. Combine
BasicBlock* bb_next = bb->fall_through;
DCHECK(!bb_next->catch_entry);
DCHECK_EQ(Predecessors(bb_next), 1U);
MIR* t_mir = bb->last_mir_insn->prev;
// Overwrite the kOpCheck insn with the paired opcode
DCHECK_EQ(bb_next->first_mir_insn, throw_insn);
*bb->last_mir_insn = *throw_insn;
bb->last_mir_insn->prev = t_mir;
// Use the successor info from the next block
bb->successor_block_list = bb_next->successor_block_list;
// Use the ending block linkage from the next block
bb->fall_through = bb_next->fall_through;
bb->taken->block_type = kDead; // Kill the unused exception block
bb->taken = bb_next->taken;
// Include the rest of the instructions
bb->last_mir_insn = bb_next->last_mir_insn;
/*
* If lower-half of pair of blocks to combine contained a return, move the flag
* to the newly combined block.
*/
bb->terminated_by_return = bb_next->terminated_by_return;
/*
* NOTE: we aren't updating all dataflow info here. Should either make sure this pass
* happens after uses of i_dominated, dom_frontier or update the dataflow info here.
*/
// Kill bb_next and remap now-dead id to parent
bb_next->block_type = kDead;
block_id_map_.Overwrite(bb_next->id, bb->id);
// Now, loop back and see if we can keep going
}
return false;
}
/* Eliminate unnecessary null checks for a basic block. */
bool MIRGraph::EliminateNullChecks(struct BasicBlock* bb) {
if (bb->data_flow_info == NULL) return false;
/*
* Set initial state. Be conservative with catch
* blocks and start with no assumptions about null check
* status (except for "this").
*/
if ((bb->block_type == kEntryBlock) | bb->catch_entry) {
temp_ssa_register_v_->ClearAllBits();
if ((cu_->access_flags & kAccStatic) == 0) {
// If non-static method, mark "this" as non-null
int this_reg = cu_->num_dalvik_registers - cu_->num_ins;
temp_ssa_register_v_->SetBit(this_reg);
}
} else if (bb->predecessors->Size() == 1) {
BasicBlock* pred_bb = bb->predecessors->Get(0);
temp_ssa_register_v_->Copy(pred_bb->data_flow_info->ending_null_check_v);
if (pred_bb->block_type == kDalvikByteCode) {
// Check to see if predecessor had an explicit null-check.
MIR* last_insn = pred_bb->last_mir_insn;
Instruction::Code last_opcode = last_insn->dalvikInsn.opcode;
if (last_opcode == Instruction::IF_EQZ) {
if (pred_bb->fall_through == bb) {
// The fall-through of a block following a IF_EQZ, set the vA of the IF_EQZ to show that
// it can't be null.
temp_ssa_register_v_->SetBit(last_insn->ssa_rep->uses[0]);
}
} else if (last_opcode == Instruction::IF_NEZ) {
if (pred_bb->taken == bb) {
// The taken block following a IF_NEZ, set the vA of the IF_NEZ to show that it can't be
// null.
temp_ssa_register_v_->SetBit(last_insn->ssa_rep->uses[0]);
}
}
}
} else {
// Starting state is intersection of all incoming arcs
GrowableArray<BasicBlock*>::Iterator iter(bb->predecessors);
BasicBlock* pred_bb = iter.Next();
DCHECK(pred_bb != NULL);
temp_ssa_register_v_->Copy(pred_bb->data_flow_info->ending_null_check_v);
while (true) {
pred_bb = iter.Next();
if (!pred_bb) break;
if ((pred_bb->data_flow_info == NULL) ||
(pred_bb->data_flow_info->ending_null_check_v == NULL)) {
continue;
}
temp_ssa_register_v_->Intersect(pred_bb->data_flow_info->ending_null_check_v);
}
}
// Walk through the instruction in the block, updating as necessary
for (MIR* mir = bb->first_mir_insn; mir != NULL; mir = mir->next) {
if (mir->ssa_rep == NULL) {
continue;
}
int df_attributes = oat_data_flow_attributes_[mir->dalvikInsn.opcode];
// Mark target of NEW* as non-null
if (df_attributes & DF_NON_NULL_DST) {
temp_ssa_register_v_->SetBit(mir->ssa_rep->defs[0]);
}
// Mark non-null returns from invoke-style NEW*
if (df_attributes & DF_NON_NULL_RET) {
MIR* next_mir = mir->next;
// Next should be an MOVE_RESULT_OBJECT
if (next_mir &&
next_mir->dalvikInsn.opcode == Instruction::MOVE_RESULT_OBJECT) {
// Mark as null checked
temp_ssa_register_v_->SetBit(next_mir->ssa_rep->defs[0]);
} else {
if (next_mir) {
LOG(WARNING) << "Unexpected opcode following new: " << next_mir->dalvikInsn.opcode;
} else if (bb->fall_through) {
// Look in next basic block
struct BasicBlock* next_bb = bb->fall_through;
for (MIR* tmir = next_bb->first_mir_insn; tmir != NULL;
tmir =tmir->next) {
if (static_cast<int>(tmir->dalvikInsn.opcode) >= static_cast<int>(kMirOpFirst)) {
continue;
}
// First non-pseudo should be MOVE_RESULT_OBJECT
if (tmir->dalvikInsn.opcode == Instruction::MOVE_RESULT_OBJECT) {
// Mark as null checked
temp_ssa_register_v_->SetBit(tmir->ssa_rep->defs[0]);
} else {
LOG(WARNING) << "Unexpected op after new: " << tmir->dalvikInsn.opcode;
}
break;
}
}
}
}
/*
* Propagate nullcheck state on register copies (including
* Phi pseudo copies. For the latter, nullcheck state is
* the "and" of all the Phi's operands.
*/
if (df_attributes & (DF_NULL_TRANSFER_0 | DF_NULL_TRANSFER_N)) {
int tgt_sreg = mir->ssa_rep->defs[0];
int operands = (df_attributes & DF_NULL_TRANSFER_0) ? 1 :
mir->ssa_rep->num_uses;
bool null_checked = true;
for (int i = 0; i < operands; i++) {
null_checked &= temp_ssa_register_v_->IsBitSet(mir->ssa_rep->uses[i]);
}
if (null_checked) {
temp_ssa_register_v_->SetBit(tgt_sreg);
}
}
// Already nullchecked?
if ((df_attributes & DF_HAS_NULL_CHKS) && !(mir->optimization_flags & MIR_IGNORE_NULL_CHECK)) {
int src_idx;
if (df_attributes & DF_NULL_CHK_1) {
src_idx = 1;
} else if (df_attributes & DF_NULL_CHK_2) {
src_idx = 2;
} else {
src_idx = 0;
}
int src_sreg = mir->ssa_rep->uses[src_idx];
if (temp_ssa_register_v_->IsBitSet(src_sreg)) {
// Eliminate the null check
mir->optimization_flags |= MIR_IGNORE_NULL_CHECK;
} else {
// Mark s_reg as null-checked
temp_ssa_register_v_->SetBit(src_sreg);
}
}
}
// Did anything change?
bool changed = !temp_ssa_register_v_->Equal(bb->data_flow_info->ending_null_check_v);
if (changed) {
bb->data_flow_info->ending_null_check_v->Copy(temp_ssa_register_v_);
}
return changed;
}
void MIRGraph::NullCheckElimination() {
if (!(cu_->disable_opt & (1 << kNullCheckElimination))) {
DCHECK(temp_ssa_register_v_ != NULL);
AllNodesIterator iter(this, false /* not iterative */);
for (BasicBlock* bb = iter.Next(); bb != NULL; bb = iter.Next()) {
NullCheckEliminationInit(bb);
}
PreOrderDfsIterator iter2(this, true /* iterative */);
bool change = false;
for (BasicBlock* bb = iter2.Next(change); bb != NULL; bb = iter2.Next(change)) {
change = EliminateNullChecks(bb);
}
}
if (cu_->enable_debug & (1 << kDebugDumpCFG)) {
DumpCFG("/sdcard/4_post_nce_cfg/", false);
}
}
void MIRGraph::BasicBlockCombine() {
PreOrderDfsIterator iter(this, false /* not iterative */);
for (BasicBlock* bb = iter.Next(); bb != NULL; bb = iter.Next()) {
CombineBlocks(bb);
}
if (cu_->enable_debug & (1 << kDebugDumpCFG)) {
DumpCFG("/sdcard/5_post_bbcombine_cfg/", false);
}
}
void MIRGraph::CodeLayout() {
if (cu_->enable_debug & (1 << kDebugVerifyDataflow)) {
VerifyDataflow();
}
AllNodesIterator iter(this, false /* not iterative */);
for (BasicBlock* bb = iter.Next(); bb != NULL; bb = iter.Next()) {
LayoutBlocks(bb);
}
if (cu_->enable_debug & (1 << kDebugDumpCFG)) {
DumpCFG("/sdcard/2_post_layout_cfg/", true);
}
}
void MIRGraph::DumpCheckStats() {
Checkstats* stats =
static_cast<Checkstats*>(arena_->Alloc(sizeof(Checkstats), ArenaAllocator::kAllocDFInfo));
checkstats_ = stats;
AllNodesIterator iter(this, false /* not iterative */);
for (BasicBlock* bb = iter.Next(); bb != NULL; bb = iter.Next()) {
CountChecks(bb);
}
if (stats->null_checks > 0) {
float eliminated = static_cast<float>(stats->null_checks_eliminated);
float checks = static_cast<float>(stats->null_checks);
LOG(INFO) << "Null Checks: " << PrettyMethod(cu_->method_idx, *cu_->dex_file) << " "
<< stats->null_checks_eliminated << " of " << stats->null_checks << " -> "
<< (eliminated/checks) * 100.0 << "%";
}
if (stats->range_checks > 0) {
float eliminated = static_cast<float>(stats->range_checks_eliminated);
float checks = static_cast<float>(stats->range_checks);
LOG(INFO) << "Range Checks: " << PrettyMethod(cu_->method_idx, *cu_->dex_file) << " "
<< stats->range_checks_eliminated << " of " << stats->range_checks << " -> "
<< (eliminated/checks) * 100.0 << "%";
}
}
bool MIRGraph::BuildExtendedBBList(struct BasicBlock* bb) {
if (bb->visited) return false;
if (!((bb->block_type == kEntryBlock) || (bb->block_type == kDalvikByteCode)
|| (bb->block_type == kExitBlock))) {
// Ignore special blocks
bb->visited = true;
return false;
}
// Must be head of extended basic block.
BasicBlock* start_bb = bb;
extended_basic_blocks_.push_back(bb);
bool terminated_by_return = false;
// Visit blocks strictly dominated by this head.
while (bb != NULL) {
bb->visited = true;
terminated_by_return |= bb->terminated_by_return;
bb = NextDominatedBlock(bb);
}
if (terminated_by_return) {
// This extended basic block contains a return, so mark all members.
bb = start_bb;
while (bb != NULL) {
bb->dominates_return = true;
bb = NextDominatedBlock(bb);
}
}
return false; // Not iterative - return value will be ignored
}
void MIRGraph::BasicBlockOptimization() {
if (!(cu_->disable_opt & (1 << kBBOpt))) {
DCHECK_EQ(cu_->num_compiler_temps, 0);
ClearAllVisitedFlags();
PreOrderDfsIterator iter2(this, false /* not iterative */);
for (BasicBlock* bb = iter2.Next(); bb != NULL; bb = iter2.Next()) {
BuildExtendedBBList(bb);
}
// Perform extended basic block optimizations.
for (unsigned int i = 0; i < extended_basic_blocks_.size(); i++) {
BasicBlockOpt(extended_basic_blocks_[i]);
}
}
if (cu_->enable_debug & (1 << kDebugDumpCFG)) {
DumpCFG("/sdcard/6_post_bbo_cfg/", false);
}
}
} // namespace art