Re: TREE_CODE mania

[Devang Patel <dpatel@apple.com>]

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On Tuesday, September 3, 2002, at 08:51 PM, Daniel Berlin wrote:

> On Tue, 3 Sep 2002, Devang Patel wrote:
>
>> Hi All,
>>
>> Recently there was a discussion about faster compile time. And
>> memory usage and/or allocation is considered one probable
>> culprit behind the slow compiler.
>>
>> To understand actual memory usage pattern, I instrumented GCC
>> by replacing TREE_CODE macro with function TREE_CODE_read().
>> I just wanted to see what is the usage pattern and how bad/good is it.
>>
>> I collected profiled data for following one line program.
>>
>> int foo() { return 1;}
>>
>> Now, gprof tells me that to compile this, cc1 calls TREE_CODE_read()
>> 37572 times! I was expecting that number to be in couple of thousands
>> range but 37k seems high to me.
>>
>> I think, such a high number of indirect memory references puts
>> high  pressure on VM and GCC's memory manager to maintain locality.
>
> Which it doesn't.
> Can't we attack this problem directly?
> By maybe using object based bins rather than size based ones, at least 
> for
> trees and RTL?

Sure, we can try using different allocation schemes to achieve better 
compile
time performance. But this approach is like -- earn more money and 
allocate
funds in better way to meet the budget. I am thinking in terms, can we 
reduce
expenditure ? I think, we need to work in both direction to achieve 
better
compile time speedup.

-Devang

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On Tuesday, September 3, 2002, at 08:51 PM, Daniel Berlin wrote:


<excerpt>On Tue, 3 Sep 2002, Devang Patel wrote:


<excerpt>Hi All,


Recently there was a discussion about faster compile time. And

memory usage and/or allocation is considered one probable

culprit behind the slow compiler.


To understand actual memory usage pattern, I instrumented GCC

by replacing TREE_CODE macro with function TREE_CODE_read().

I just wanted to see what is the usage pattern and how bad/good is it.


I collected profiled data for following one line program.


int foo() { return 1;}


Now, gprof tells me that to compile this, cc1 calls TREE_CODE_read()

37572 times! I was expecting that number to be in couple of thousands

range but 37k seems high to me.


I think, such a high number of indirect memory references puts

high  pressure on VM and GCC's memory manager to maintain locality.

</excerpt>

Which it doesn't.

Can't we attack this problem directly?

By maybe using object based bins rather than size based ones, at least
for 

trees and RTL?

</excerpt>

Sure, we can try using different allocation schemes to achieve better
compile

time performance. But this approach is like -- earn more money and
allocate 

funds in better way to meet the budget. I am thinking in terms, can we
reduce

expenditure ? I think, we need to work in both direction to achieve
better

compile time speedup.


-Devang