Reland parts of 'Use weak cells in map checks in polymorphic ICs'

src/mips64/macro-assembler-mips64.h

Index: src/mips64/macro-assembler-mips64.h
diff --git a/src/mips64/macro-assembler-mips64.h b/src/mips64/macro-assembler-mips64.h
index 95d6c785f0e05978f97c2ee2af89a2cb3294bdba..f0f009f3e56c53435030948c2cde5334b4a36e94 100644
--- a/src/mips64/macro-assembler-mips64.h
+++ b/src/mips64/macro-assembler-mips64.h
@@ -1121,6 +1121,13 @@ class MacroAssembler: public Assembler {
                    Handle<Code> success,
                    SmiCheckType smi_check_type);
 
+  // Compare the given value and the value of the weak cell. Write the result
+  // to the match register.
+  void CmpWeakValue(Register match, Register value, Handle<WeakCell> cell);
+
+  // Load the value of the weak cell in the value register. Branch to the
+  // given miss label is the weak cell was cleared.
+  void LoadWeakValue(Register value, Handle<WeakCell> cell, Label* miss);
 
   // Load and check the instance type of an object for being a string.
   // Loads the type into the second argument register.