On Thu, Oct 11, 2012 at 8:50 AM, Bin Cheng wrote:
> + /* x+y won't be hoisted without defaultly enabled "-fira-hoist-pressure",
defaulty comment.
> + kinds of code motion(including code hoisting) in a unified way.
needs space between "motion" and "(".
> + flow graph, given if it can reach BB unimpared. Stop the search if the
s/given if/if/
> +should_hoist_expr_to_dom (basic_block expr_bb, struct expr *expr,
> + basic_block bb, sbitmap visited, int distance,
> + int *bb_size, enum reg_class pressure_class,
> + int *nregs, bitmap hoisted_bbs)
At least BB_SIZE and DISTANCE are not documented (also not before your
patch). While there, can you document these please?
> + becasue hoisting constant expr aggresively results in worse code
> + as observed. */
s/becasue/because/
s/aggresively/aggressively/
Not sure what you mean with "as observed". Observed where/how?
> - visited = XCNEWVEC (char, last_basic_block);
> + visited = sbitmap_alloc (last_basic_block);
> + sbitmap_zero (visited);
Send a separate patch for this change please. Really. Reviewing
patches is much easier if you post things one change at a time.
> + The code hoisting pass hoists multiple computations of expression
> + to dominator basic block, like from b2/b3 to b1 as depicted below:
"The code hoisting pass can hoist multiple computations of the same
expression along dominated paths to a dominating basic block, like
from ..."
> + Unfortunately code hoisting generally extend live range of output
s/extend/extends the/
s/of output/of an output/
> + from rtx cost of corresponding expression and it's used to control
s/of corresponding/of the corresponding/
Similarly elsewhere in comments.
> + of shrinked live range of input pseudo register when hoisting an
s/range/ranges/
s/register/registers/
After all this is only possible, AFAICT, if there's more than one
input register.
I'll leave all the algorithmic stuff to Jeff...
Ciao!
Steven
