Merge "Fix suspend check optimization" into dalvik-dev

4 files changed, 20 insertions, 12 deletions

diff --git a/compiler/dex/mir_graph.cc b/compiler/dex/mir_graph.cc
index 86f6ee5..5732dce 100644
--- a/compiler/dex/mir_graph.cc
+++ b/compiler/dex/mir_graph.cc
@@ -306,6 +306,9 @@ BasicBlock* MIRGraph::ProcessCanBranch(BasicBlock* cur_block, MIR* insn, int cur
     default:
       LOG(FATAL) << "Unexpected opcode(" << insn->dalvikInsn.opcode << ") with kBranch set";
   }
+  if (target <= cur_offset) {
+    insn->backwards_branch = true;
+  }
   BasicBlock *taken_block = FindBlock(target, /* split */ true, /* create */ true,
                                       /* immed_pred_block_p */ &cur_block);
   cur_block->taken = taken_block;
diff --git a/compiler/dex/mir_graph.h b/compiler/dex/mir_graph.h
index 84ab259..45e425b 100644
--- a/compiler/dex/mir_graph.h
+++ b/compiler/dex/mir_graph.h
@@ -232,7 +232,8 @@ struct SSARepresentation {
  */
 struct MIR {
   DecodedInstruction dalvikInsn;
-  unsigned int width;
+  uint16_t width;
+  bool backwards_branch;          // TODO: may be useful to make this an attribute flag word.
   unsigned int offset;
   int m_unit_index;               // From which method was this MIR included
   MIR* prev;
diff --git a/compiler/dex/mir_optimization.cc b/compiler/dex/mir_optimization.cc
index a6314f4..82ba6e3 100644
--- a/compiler/dex/mir_optimization.cc
+++ b/compiler/dex/mir_optimization.cc
@@ -153,7 +153,14 @@ static BasicBlock* NextDominatedBlock(BasicBlock* bb) {
   }
   DCHECK((bb->block_type == kEntryBlock) || (bb->block_type == kDalvikByteCode)
       || (bb->block_type == kExitBlock));
-  bb = bb->fall_through;
+  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;
   }
@@ -303,7 +310,8 @@ bool MIRGraph::BasicBlockOpt(BasicBlock* bb) {
         case Instruction::IF_GEZ:
         case Instruction::IF_GTZ:
         case Instruction::IF_LEZ:
-          if (bb->taken->dominates_return) {
+          // If we've got a backwards branch to return, no need to suspend check.
+          if ((bb->taken->dominates_return) && (mir->backwards_branch)) {
             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;
diff --git a/compiler/dex/quick/mir_to_lir.cc b/compiler/dex/quick/mir_to_lir.cc
index 74eaa66..8f42999 100644
--- a/compiler/dex/quick/mir_to_lir.cc
+++ b/compiler/dex/quick/mir_to_lir.cc
@@ -239,7 +239,7 @@ void Mir2Lir::CompileDalvikInstruction(MIR* mir, BasicBlock* bb, LIR* label_list
     case Instruction::GOTO:
     case Instruction::GOTO_16:
     case Instruction::GOTO_32:
-      if (bb->taken->start_offset <= mir->offset) {
+      if (mir->backwards_branch) {
         GenSuspendTestAndBranch(opt_flags, &label_list[bb->taken->id]);
       } else {
         OpUnconditionalBranch(&label_list[bb->taken->id]);
@@ -273,19 +273,17 @@ void Mir2Lir::CompileDalvikInstruction(MIR* mir, BasicBlock* bb, LIR* label_list
     case Instruction::IF_LE: {
       LIR* taken = &label_list[bb->taken->id];
       LIR* fall_through = &label_list[bb->fall_through->id];
-      bool backward_branch;
-      backward_branch = (bb->taken->start_offset <= mir->offset);
       // Result known at compile time?
       if (rl_src[0].is_const && rl_src[1].is_const) {
         bool is_taken = EvaluateBranch(opcode, mir_graph_->ConstantValue(rl_src[0].orig_sreg),
                                        mir_graph_->ConstantValue(rl_src[1].orig_sreg));
-        if (is_taken && backward_branch) {
+        if (is_taken && mir->backwards_branch) {
           GenSuspendTest(opt_flags);
         }
         int id = is_taken ? bb->taken->id : bb->fall_through->id;
         OpUnconditionalBranch(&label_list[id]);
       } else {
-        if (backward_branch) {
+        if (mir->backwards_branch) {
           GenSuspendTest(opt_flags);
         }
         GenCompareAndBranch(opcode, rl_src[0], rl_src[1], taken,
@@ -302,18 +300,16 @@ void Mir2Lir::CompileDalvikInstruction(MIR* mir, BasicBlock* bb, LIR* label_list
     case Instruction::IF_LEZ: {
       LIR* taken = &label_list[bb->taken->id];
       LIR* fall_through = &label_list[bb->fall_through->id];
-      bool backward_branch;
-      backward_branch = (bb->taken->start_offset <= mir->offset);
       // Result known at compile time?
       if (rl_src[0].is_const) {
         bool is_taken = EvaluateBranch(opcode, mir_graph_->ConstantValue(rl_src[0].orig_sreg), 0);
-        if (is_taken && backward_branch) {
+        if (is_taken && mir->backwards_branch) {
           GenSuspendTest(opt_flags);
         }
         int id = is_taken ? bb->taken->id : bb->fall_through->id;
         OpUnconditionalBranch(&label_list[id]);
       } else {
-        if (backward_branch) {
+        if (mir->backwards_branch) {
           GenSuspendTest(opt_flags);
         }
         GenCompareZeroAndBranch(opcode, rl_src[0], taken, fall_through);