[v8-dev] ARM: safepoints frame optimization

src/frames.cc

Index: src/frames.cc
diff --git a/src/frames.cc b/src/frames.cc
index 3b55c276cf3b4cfa6d4cb972f87370cd6bd7e5ee..e9df843e87102d2532712626b5e493f29b40ecba 100644
--- a/src/frames.cc
+++ b/src/frames.cc
@@ -652,6 +652,32 @@ void StandardFrame::IterateCompiledFrame(ObjectVisitor* v) const {
     parameters_base += safepoint_entry.argument_count();
   }
 
+#if V8_TARGET_ARCH_ARM
+  // The frame must have been generated within LCodegen::GeneratedCode where
+  // registers_mask and double_registers_mask are set.
+  ASSERT(code->registers_mask() != kRegListEmpty);
+  // Skip saved double registers.
+  if (safepoint_entry.has_doubles()) {
+    parameters_base +=
+        CompilerIntrinsics::CountSetBits(code->double_registers_mask()) *
+        kDoubleSize / kPointerSize;
+  }
+
+  // Visit the registers that contain pointers if any.
+  if (safepoint_entry.HasRegisters()) {
+    RegList registers_mask = code->registers_mask();
+    for (int i = 0; i < kNumSafepointRegisters; i++) {
+      if ((registers_mask & (1 << i)) != 0) {
+        if (safepoint_entry.HasRegisterAt(i)) {
+          v->VisitPointer(parameters_base);
+        }
+        parameters_base++;
+      } else {
+        ASSERT(!safepoint_entry.HasRegisterAt(i));
+      }
+    }
+  }
+#else
   // Skip saved double registers.
   if (safepoint_entry.has_doubles()) {
     // Number of doubles not known at snapshot time.
@@ -671,6 +697,7 @@ void StandardFrame::IterateCompiledFrame(ObjectVisitor* v) const {
     // Skip the words containing the register values.
     parameters_base += kNumSafepointRegisters;
   }
+#endif
 
   // We're done dealing with the register bits.
   uint8_t* safepoint_bits = safepoint_entry.bits();