[LLVMdev] RegAllocFast uses too much stack

[Dan Gohman]

On Jul 11, 2011, at 3:06 PM, Eli Friedman wrote:

> On Mon, Jul 11, 2011 at 2:44 PM, Eric Christopher <echristo at apple.com> wrote:
>> 
>> On Jul 11, 2011, at 1:48 PM, Nick Lewycky wrote:
>> 
>> This seems odd. I'd think that fast-isel should be able to materialize the constants when we want them rather than at the beginning of the block.
> 
> I'm not entirely sure why, but FastISel does intentionally materialize
> constants at the beginning of the block.  See
> FastISel::enterLocalValueArea etc.  Maybe Dan knows why?


Going bottom-up, FastISel doesn't know when it'll see the first use of a value
in a block. Cleverer schemes are possible.

Dan