Problem with too many virtual operands ( tree-ssa-operands.c:484)

[Andrew MacLeod]

Pranav Bhandarkar wrote:
> Hi,
> In the attached testcase due to an ivopts modification, while
> rewriting the uses the compiler crashes in tree-ssa-operands.c because
> the number of virtual operands of the modified stmt is much greater
> than the thresholds controlled by OP_SIZE_{1,2,3} in
> tree-ssa-operands.c.
>
> I went through
> http://gcc.gnu.org/ml/gcc-patches/2006-12/msg01269.html
>
> and it seemed to me that these values (OP_SIZE etc) have been quite
> experimentally set. I am wondering If these values should be
> increased.
>
>   
They are 'experimental', but the reason is to catch cases like this to 
examine.  MEM-SSA was suppose to eliminate excessively large numbers of 
virtual operands. I haven't had a chance to look at this yet, perhaps 
Diego will get a chance before I do since I'm traveling and tied up the 
rest of this week.

If it turns out there isn't something mem-ssa should be doing 
differently for this case to reduce the number of operands, we can 
either increase the thresholds, or add a 4th one for these excessive 
cases.  Im hoping there is a different solution since large numbers of 
virtuals cause lots of compile time issues. I believe the previous times 
we've triggered this (Its been a while), we made changes to the virtual 
operand processing to resolve it and save memory/compile time.

Andrew