Make x87 stack tracking more robust and avoid spilling

Make x87 stack tracking more robust and avoid spilling

BUG=

[Toon Verwaest, 2013-08-22 13:33:40]

This approach seems pretty complex. As discussed, I'm not sure it's the right
way to go.

https://codereview.chromium.org/22903028/diff/5001/src/ia32/lithium-codegen-i...
File src/ia32/lithium-codegen-ia32.cc (right):

https://codereview.chromium.org/22903028/diff/5001/src/ia32/lithium-codegen-i...
src/ia32/lithium-codegen-ia32.cc:744: continue;
As discussed, this seems broken. If we swap input variables downwards, we'll
visit them again and they'll seem like input variables again; and we won't pop
non-input-variables we just swapped. Additionally, in larger stacks, we'll never
manage to get input variables that are being swapped upwards in the right
position.

I also don't like this kind of code at all; it's very hard to understand.

[oliv, 2013-08-23 09:27:16]

On 2013/08/22 13:33:40, Toon Verwaest wrote:
> This approach seems pretty complex. As discussed, I'm not sure it's the right
> way to go.
> 
>
https://codereview.chromium.org/22903028/diff/5001/src/ia32/lithium-codegen-i...
> File src/ia32/lithium-codegen-ia32.cc (right):
> 
>
https://codereview.chromium.org/22903028/diff/5001/src/ia32/lithium-codegen-i...
> src/ia32/lithium-codegen-ia32.cc:744: continue;
> As discussed, this seems broken. If we swap input variables downwards, we'll
> visit them again and they'll seem like input variables again; and we won't pop
> non-input-variables we just swapped. Additionally, in larger stacks, we'll
never
> manage to get input variables that are being swapped upwards in the right
> position.
> 
> I also don't like this kind of code at all; it's very hard to understand.

ok, lets put this on hold as it doesn't really pay off. i'll just try to fix the
immediate problems then...