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 36aec4544625783653567becf52f1483eb42d1d5..88e38338bdbcaf05139987dc6902a2b93702bdc1 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -325,47 +325,59 @@ bool LCodeGen::GenerateDeoptJumpTable() {
 
   if (deopt_jump_table_.length() > 0) {
     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 {
+    Label table_start;
+    __ bind(&table_start);
+    Label needs_frame, call_l2;
+    Address base = deopt_jump_table_[0].address;
+    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;
+      ASSERT(type == deopt_jump_table_[0].bailout_type);
+      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(scratch0(), 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);
+          __ 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));
+          // Add the base address to the offset previously loaded in scratch0.
+          __ add(scratch0(), scratch0(),

[ulan, 2014/06/23 11:41:40]

Any reason you didn't move this out of the loop like it is done in r21608?

[vincent.belliard, 2014/06/23 11:52:29]

Both versions generate the same number of instructions. I left in the loop
because that what was done before for ARM (and I think it's a little bit easier
to read).
Do you want me to put it out of the loop?

[vincent.belliard, 2014/06/24 14:28:17]

Done.

+                 Operand(ExternalReference::ForDeoptEntry(base)));
+          __ blx(scratch0());
+        }
       } 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);
-      }
-    } else {
-      if (info()->saves_caller_doubles()) {
-        ASSERT(info()->IsStub());
-        RestoreCallerDoubles();
+        if (call_l2.is_bound()) {
+          __ b(&call_l2);
+        } else {
+          __ bind(&call_l2);
+          if (info()->saves_caller_doubles()) {
+            ASSERT(info()->IsStub());
+            RestoreCallerDoubles();
+          }
+          // Add the base address to the offset previously loaded in scratch0.
+          __ add(scratch0(), scratch0(),
+                 Operand(ExternalReference::ForDeoptEntry(base)));
+          __ blx(scratch0());
+        }
       }
-      __ mov(lr, Operand(pc), LeaveCC, al);
-      __ mov(pc, Operand(ExternalReference::ForDeoptEntry(entry)));
+      masm()->CheckConstPool(false, false);
     }
-    masm()->CheckConstPool(false, false);
   }
 
   // Force constant pool emission at the end of the deopt jump table to make