panic when compiling SHA

[Ben Lippmeier]

On 04/01/2014, at 23:22 , Kazu Yamamoto (山本和彦) <kazu at iij.ad.jp> wrote:

> Hi,
> 
>>> There are only a fixed number of register spill slots, and when
>>> they're all used the compiler can't dynamically allocate more of
>>> them.
>> 
>> Not true any more in 7.8+ with the linear allocator.  I think it might
>> still be true for the graph allocator, which is sadly suffering from a
>> little bitrot and probably doesn't generate very good code with the
>> new code generator.
>> 
>> So, avoiding -fregs-graph should work around this with 7.8.
> 
> I confirmed that removing -fregs-graph should work around this with
> 7.8.

Ok, my mistake. We originally added -fregs-graph when compiling that module because both allocators had a fixed stack size, but the graph allocator did a better job of allocation and avoided overflowing the stack.

Note that removing the flag isn't a "solution" to the underlying problem of the intermediate code being awful. Switching to the linear allocator just permits compilation of core code that was worse than before. Now it needs to spill more registers when compiling the same source code.

Ben.