[LLVMdev] RegAllocFast uses too much stack

Dan Gohman gohman at apple.com
Mon Jul 11 15:41:00 PDT 2011

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.


More information about the llvm-dev mailing list