Simple type tracking in the fast code generator.

src/fast-codegen.h

Index: src/fast-codegen.h
diff --git a/src/fast-codegen.h b/src/fast-codegen.h
index 5bc03374e09224d2264bbd68b2ae97429068431a..a784381a90522de68182bc188c0f7d148546c847 100644
--- a/src/fast-codegen.h
+++ b/src/fast-codegen.h
@@ -97,6 +97,12 @@ class FastCodeGenerator: public AstVisitor {
     return (reg.is(accumulator0())) ? accumulator1() : accumulator0();
   }
 
+  // Flags are true if the respective register is statically known to hold a
+  // smi.  We do not track every register, only the accumulator registers.
+  bool is_smi(Register reg) { return (smi_bits_ & reg.bit()) != 0; }

[fschneider, 2010/02/10 15:14:33]

What happens if reg == no_reg? Maybe we should 
ASSERT(reg != noreg) here, since reg.bit() of no_reg is -1.

[Kevin Millikin (Chromium), 2010/02/11 08:30:09]

Done.

+  void set_as_smi(Register reg) { smi_bits_ = smi_bits_ | reg.bit(); }
+  void clear_as_smi(Register reg) { smi_bits_ = smi_bits_ & ~reg.bit(); }
+
   // AST node visit functions.
 #define DECLARE_VISIT(type) virtual void Visit##type(type* node);
   AST_NODE_LIST(DECLARE_VISIT)
@@ -129,6 +135,7 @@ class FastCodeGenerator: public AstVisitor {
   CompilationInfo* info_;
   Label bailout_;
   Register destination_;
+  uint32_t smi_bits_;

[fschneider, 2010/02/10 15:14:33]

smi_bits_ should be initialized to 0?

[Kevin Millikin (Chromium), 2010/02/11 08:30:09]

Done.

 
   DISALLOW_COPY_AND_ASSIGN(FastCodeGenerator);
 };