Re: [PATCH] fwprop: Prevent infinite looping (PR79405)

2017-03-31 Thread Jeff Law
On 03/23/2017 08:58 AM, Segher Boessenkool wrote: The algorithm fwprop uses never reconsiders a possible propagation, although it could succeed if the def (in the def-use to propagate) has changed. This causes fwprop to do infinite propagations, like in the scenario in the PR, where we end up

Re: [PATCH] fwprop: Prevent infinite looping (PR79405)

2017-03-24 Thread Segher Boessenkool
On Fri, Mar 24, 2017 at 12:54:35PM +0100, Richard Biener wrote: > > I have implemented the "retry things" as well fwiw, but a) it is too > > big and invasive for stage 4, and b) it kind of sucks, needs more > > work, even more invasive. The workaround is cheap and solves the > > immediate

Re: [PATCH] fwprop: Prevent infinite looping (PR79405)

2017-03-24 Thread Jeff Law
On 03/24/2017 05:54 AM, Richard Biener wrote: On Fri, Mar 24, 2017 at 10:39 AM, Segher Boessenkool wrote: On Fri, Mar 24, 2017 at 09:13:59AM +0100, Richard Biener wrote: https://gcc.gnu.org/ml/gcc-patches/2017-02/msg01485.html ? What about it? That suggestion

Re: [PATCH] fwprop: Prevent infinite looping (PR79405)

2017-03-24 Thread Richard Biener
On Fri, Mar 24, 2017 at 10:39 AM, Segher Boessenkool wrote: > On Fri, Mar 24, 2017 at 09:13:59AM +0100, Richard Biener wrote: >> >> https://gcc.gnu.org/ml/gcc-patches/2017-02/msg01485.html >> >> >> >> ? >> > >> > What about it? That suggestion would make fwprop do

Re: [PATCH] fwprop: Prevent infinite looping (PR79405)

2017-03-24 Thread Segher Boessenkool
On Fri, Mar 24, 2017 at 09:13:59AM +0100, Richard Biener wrote: > >> https://gcc.gnu.org/ml/gcc-patches/2017-02/msg01485.html > >> > >> ? > > > > What about it? That suggestion would make fwprop do *less* useful work, > > while in principle the problem is that it *already* does not enough! > >

Re: [PATCH] fwprop: Prevent infinite looping (PR79405)

2017-03-24 Thread Richard Biener
On Thu, Mar 23, 2017 at 4:45 PM, Segher Boessenkool wrote: > On Thu, Mar 23, 2017 at 04:16:56PM +0100, Richard Biener wrote: >> On Thu, Mar 23, 2017 at 3:58 PM, Segher Boessenkool >> wrote: >> > The algorithm fwprop uses never reconsiders a

Re: [PATCH] fwprop: Prevent infinite looping (PR79405)

2017-03-23 Thread Segher Boessenkool
On Thu, Mar 23, 2017 at 04:16:56PM +0100, Richard Biener wrote: > On Thu, Mar 23, 2017 at 3:58 PM, Segher Boessenkool > wrote: > > The algorithm fwprop uses never reconsiders a possible propagation, > > although it could succeed if the def (in the def-use to propagate)

Re: [PATCH] fwprop: Prevent infinite looping (PR79405)

2017-03-23 Thread Richard Biener
On Thu, Mar 23, 2017 at 3:58 PM, Segher Boessenkool wrote: > The algorithm fwprop uses never reconsiders a possible propagation, > although it could succeed if the def (in the def-use to propagate) > has changed. This causes fwprop to do infinite propagations, like >

[PATCH] fwprop: Prevent infinite looping (PR79405)

2017-03-23 Thread Segher Boessenkool
The algorithm fwprop uses never reconsiders a possible propagation, although it could succeed if the def (in the def-use to propagate) has changed. This causes fwprop to do infinite propagations, like in the scenario in the PR, where we end up with effectively B = A A = B D = A where only