[fpc-devel] crash with -gt -O2 (regvar) in trunk

[Jonas Maebe]

On 07 Jun 2010, at 18:40, Martin wrote:

> In this case the result should be the same, and since both cases are using both registers, the 2 registers should in both cases be avail for usage.
> 
> I wonder if in other cases, eax may drop in for edx (or vice versa) where it may cause a proble (data replaced?)
> 
> The question is, should -gt have caused this change?

The register allocator uses a graph colouring algorithm. It can easily produce slightly different but equivalent register allocations when the graphs change (i.e., when more virtual registers are used, e.g. because of extra initialisation code). So yes, it is entirely expected that such changes occur with -gt.


Jonas