[Tinycc-devel] Re: Please comment this patch, if you have the time.

[Rob Landley]

On Tuesday 25 September 2007 3:54:23 pm Jakob Eriksson wrote:
> +int gen_0x850f(int ind)
> +{
> +    o(0x1A000000 | encbranch(ind, 0, 1));
> +
> +    return ind;
> +}

Getting back to "that's a horrible name for this proposed function"...

Let's see, according to http://sandpile.org/ia32 the opcode 0x85 is "TEST 
Eb,Gb" and 0x0f is the prefix to indicate a two byte opcode follows.  At a 
guess the function name indicates an x86 "test and jump".

Except that the function _contents_ start by sticking 0x1a at the start of it, 
which is "SBB Gb, Eb" and I have no _IDEA_ what that means, but google 
probably will...  http://en.wikipedia.org/wiki/X86_assembly_language
says "subtraction with borrow".  Ok...

Anybody else understand what this is doing?

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.