Re: PATCH RFA: Split stack [3/7]: CFG build probability

[Ian Lance Taylor <iant at google dot com>]

Ian Lance Taylor <iant@google.com> writes:

> This is the third of the -fsplit-stack patches.  This adds a new feature
> to the CFG builder: if an edge is created because of a jump insn, and
> the jump insn has a REG_BR_PROB note, then we copy the probability from
> the note to the edge.  This is useful because the split stack prologue
> code has a branch, and the branch has a probability.  This permits the
> code to set a probability on the branch and have that probability be
> carried into the CFG.
>
> An alternative would be to have the split stack prologue code create
> basic blocks itself.  However at present there is other RTL level code
> which creates branches on edges, which the CFG code knows how to
> incorporate into the CFG, and I see no harm in continuing this existing
> facility.
>
> This code is in the middle-end and as such I do not require approval,
> but I would like to see any comments or objections to this approach.
>
> Ian
>
>
> 2010-09-21  Ian Lance Taylor  <iant@google.com>
>
> 	* cfgbuild.c (make_label_edge): Add insn parameter.  Change all
> 	callers.  If insn has a REG_BR_PROB note, copy it to the edge
> 	probability.

Honza questioned why this patch was needed, and he was right: it does
not appear to be required.  I do not know why I needed to write it when
I did the original work.

Please consider this patch withdrawn.  Sorry for taking up people's time
with it.

I think at this point I have received all the approvals and comments I
need for the split stack patch, and I plan to do some final testing and
go ahead and commit on Monday.

Ian