Re: [9fans] 8a/8l bug

[Latchesar Ionkov <lucho@ionkov.net>]

On Wed, Dec 17, 2003 at 06:38:22PM -0500, Russ Cox said:
> > 1. Adds a new option whether to do instruction optimizations.
> > 2. Modifies y* arrays to have a flag whether the instruction code should be
> > used if the optimizations are on.
>
> I don't want a flag to fix broken behavior.
> I want the linker to do the right thing.
>
> I'd rather change the linker just to drop the
> INCL/DECL as possible ADDL/SUBL encodings
> and then change the compiler if the hit is actually
> significant (seems like it could be).
>
> How many other instructions are affected?
>
> > 3. Optionally the flag also holds information whether the specific
> > instruction has 0x0f/0x66 headers overriding the default specified in the
> > optab array.
>
> If you need this to handle certain instructions, then this seems
> reasonable, although I'm not sure I understand why it can't
> be handled with just a separate line in the y* array.

The flag if there should be 0x0f or 0x66 header is defined per opcode (Pm,
Pe) in optab instead of being defined per line in y*.

I already changed the machine description in gcc to avoid the problem, so I
don't need it badly, but gcc generates suboptimal code now.

BTW currently gcc compiles and executes correctly about 95% of the testcases
for C that come with it. Currently I am using gcc hosted in Linux. It uses
8a and 8l to generate the executables. When I get 98% of the testcases
correctly, I'll try C++.