ARM: sligthly reduce deopt tables size

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 14c34cab2c02e5bc384f2414f3977fd67dda6044..4da7c94cb0c4bf4585f43a2f7666037c84b33be2 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -324,48 +324,79 @@ bool LCodeGen::GenerateDeoptJumpTable() {
   }
 
   if (deopt_jump_table_.length() > 0) {
+    Label needs_frame, call_deopt_entry;
+
     Comment(";;; -------------------- Jump table --------------------");
-  }
-  Label table_start;
-  __ bind(&table_start);
-  Label needs_frame;
-  for (int i = 0; i < deopt_jump_table_.length(); i++) {
-    __ bind(&deopt_jump_table_[i].label);
-    Address entry = deopt_jump_table_[i].address;
-    Deoptimizer::BailoutType type = deopt_jump_table_[i].bailout_type;
-    int id = Deoptimizer::GetDeoptimizationId(isolate(), entry, type);
-    if (id == Deoptimizer::kNotDeoptimizationEntry) {
-      Comment(";;; jump table entry %d.", i);
-    } else {
+    Address base = deopt_jump_table_[0].address;
+
+    Register entry_offset = scratch0();
+
+    int length = deopt_jump_table_.length();
+    for (int i = 0; i < length; i++) {
+      __ bind(&deopt_jump_table_[i].label);
+
+      Deoptimizer::BailoutType type = deopt_jump_table_[i].bailout_type;
+      ASSERT(type == deopt_jump_table_[0].bailout_type);
+      Address entry = deopt_jump_table_[i].address;
+      int id = Deoptimizer::GetDeoptimizationId(isolate(), entry, type);
+      ASSERT(id != Deoptimizer::kNotDeoptimizationEntry);
       Comment(";;; jump table entry %d: deoptimization bailout %d.", i, id);
-    }
-    if (deopt_jump_table_[i].needs_frame) {
-      ASSERT(!info()->saves_caller_doubles());
-      __ mov(ip, Operand(ExternalReference::ForDeoptEntry(entry)));
-      if (needs_frame.is_bound()) {
-        __ b(&needs_frame);
+
+      // Second-level deopt table entries are contiguous and small, so instead
+      // of loading the full, absolute address of each one, load an immediate
+      // offset which will be added to the base address later.
+      __ mov(entry_offset, Operand(entry - base));
+
+      if (deopt_jump_table_[i].needs_frame) {
+        ASSERT(!info()->saves_caller_doubles());
+        if (needs_frame.is_bound()) {
+          __ b(&needs_frame);
+        } else {
+          __ bind(&needs_frame);
+          Comment(";;; call deopt with frame");
+          __ PushFixedFrame();
+          // This variant of deopt can only be used with stubs. Since we don't
+          // have a function pointer to install in the stack frame that we're
+          // building, install a special marker there instead.
+          ASSERT(info()->IsStub());
+          __ mov(ip, Operand(Smi::FromInt(StackFrame::STUB)));
+          __ push(ip);
+          __ add(fp, sp,
+                 Operand(StandardFrameConstants::kFixedFrameSizeFromFp));
+          __ bind(&call_deopt_entry);
+          // Add the base address to the offset previously loaded in
+          // entry_offset.
+          __ add(entry_offset, entry_offset,
+                 Operand(ExternalReference::ForDeoptEntry(base)));
+          __ blx(entry_offset);
+        }
+
+        masm()->CheckConstPool(false, false);
       } else {
-        __ bind(&needs_frame);
-        __ PushFixedFrame();
-        // This variant of deopt can only be used with stubs. Since we don't
-        // have a function pointer to install in the stack frame that we're
-        // building, install a special marker there instead.
-        ASSERT(info()->IsStub());
-        __ mov(scratch0(), Operand(Smi::FromInt(StackFrame::STUB)));
-        __ push(scratch0());
-        __ add(fp, sp, Operand(StandardFrameConstants::kFixedFrameSizeFromFp));
-        __ mov(lr, Operand(pc), LeaveCC, al);
-        __ mov(pc, ip);
+        // The last entry can fall through into `call_deopt_entry`, avoiding a
+        // branch.
+        bool need_branch = ((i + 1) != length) || call_deopt_entry.is_bound();
+
+        if (need_branch) __ b(&call_deopt_entry);
+
+        masm()->CheckConstPool(false, !need_branch);
       }
-    } else {
+    }
+
+    if (!call_deopt_entry.is_bound()) {
+      Comment(";;; call deopt");
+      __ bind(&call_deopt_entry);
+
       if (info()->saves_caller_doubles()) {
         ASSERT(info()->IsStub());
         RestoreCallerDoubles();
       }
-      __ mov(lr, Operand(pc), LeaveCC, al);
-      __ mov(pc, Operand(ExternalReference::ForDeoptEntry(entry)));
+
+      // Add the base address to the offset previously loaded in entry_offset.
+      __ add(entry_offset, entry_offset,
+             Operand(ExternalReference::ForDeoptEntry(base)));
+      __ blx(entry_offset);
     }
-    masm()->CheckConstPool(false, false);
   }
 
   // Force constant pool emission at the end of the deopt jump table to make