Add signed/unsigned 8-bit and 16-bit Representations

src/hydrogen-instructions.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2838 matching lines @@
           : new(zone) Range();
       result->Shl(c->Integer32Value());
       return result;
     }
   }
   return HValue::InferRange(zone);
 }
 
 
 Range* HLoadNamedField::InferRange(Zone* zone) {
-  if (access().representation().IsByte()) {
+  if (access().representation().IsInteger8()) {
+    return new(zone) Range(-128, 127);
+  }
+  if (access().representation().IsUInteger8()) {
     return new(zone) Range(0, 255);
   }
+  if (access().representation().IsInteger16()) {
+    return new(zone) Range(-16384, 16383);

[Yang, 2013/11/07 09:32:43]

Afaik signed integer goes from -2^15 to 2^15-1, which is -32768 to 32767.

I suggest introducing kMaxInt8, kMinInt8, etc. to globals.h and define them
either as -(1<<7) and (1<<7)-1 or -0x80 and 0x7f. 

[danno, 2013/11/07 13:19:57]

Done.

+  }
+  if (access().representation().IsUInteger16()) {
+    return new(zone) Range(0, 65535);

[Yang, 2013/11/07 09:32:43]

Same here. Using a constant would be better.

[danno, 2013/11/07 13:19:57]

Done.

+  }
   if (access().IsStringLength()) {
     return new(zone) Range(0, String::kMaxLength);
   }
   return HValue::InferRange(zone);
 }
 
 
 Range* HLoadKeyed::InferRange(Zone* zone) {
   switch (elements_kind()) {
     case EXTERNAL_PIXEL_ELEMENTS:
       return new(zone) Range(0, 255);

[Yang, 2013/11/07 09:32:43]

While you are at it, this part can also be constantified.

[danno, 2013/11/07 13:19:57]

Done.

     case EXTERNAL_BYTE_ELEMENTS:
       return new(zone) Range(-128, 127);
     case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
       return new(zone) Range(0, 255);
     case EXTERNAL_SHORT_ELEMENTS:
       return new(zone) Range(-32768, 32767);
     case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
       return new(zone) Range(0, 65535);
     default:
       return HValue::InferRange(zone);
@@ skipping 1415 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal