On 09/04/14 14:04, David Malcolm wrote:
On Tue, 2014-09-02 at 19:50 +0200, Andi Kleen wrote:
I suspect the bulk of them currently are coming from the safe_as_a
<rtx_insn *> calls within NEXT_INSN and PREV_INSN; do you happen to have
information handy on that?
Yes that's right:
- 1.03% lto1 [.] bool
is_a_helper<rtx_insn*>::test<rtx_def>(rtx_def*)
▒
- bool is_a_helper<rtx_insn*>::test<rtx_def>(rtx_def*)
▒
- 92.20% bool is_a<rtx_insn*, rtx_def>(rtx_def*)
▒
- 98.53% rtx_insn* safe_as_a<rtx_insn*, rtx_def>(rtx_def*)
▒
- 73.28% NEXT_INSN(rtx_insn const*)
▒
The is_a_helper for rtx_insn * is non-trivial, so it may be worth
avoiding it, even when inlined.
The attached patch rewrites the inline NEXT_INSN/PREV_INSN to avoid
doing the safe_as_a, instead tightening up the interface so that one can
only set them to an insn, and introducing a new XINSN access macro and
corresponding rt_insn member of the union.
Bootstrapped on x86_64-unknown-linux-gnu (Fedora 20), and has been
rebuilt as part of a config-list.mk build for all working configurations
(albeit with other patches for the latter case).
OK for trunk?
So is this just to deal with the overhead in the safe_as_a helper until
we can strengthen more code? And is that overhead significant in an
optimized build?
Would an alternate approach be to make the checking in safe_as_a
conditionalized on ENABLE_CHECKING?
jeff
