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Re: Combined top-down and bottom-up instruction scheduler
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Aditya K <hiraditya at msn dot com>
- Cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>, "vmakarov at redhat dot com" <vmakarov at redhat dot com>, "law at redhat dot com" <law at redhat dot com>
- Date: Tue, 8 Sep 2015 13:48:23 -0500
- Subject: Re: Combined top-down and bottom-up instruction scheduler
- Authentication-results: sourceware.org; auth=none
- References: <BLU179-W6188AF5C5B442B4282F2F0B6530 at phx dot gbl>
On Tue, Sep 08, 2015 at 06:39:19PM +0000, Aditya K wrote:
> IIUC, in the haifa-sched.c, the default scheduling algorithm seems to be top-down (before reload).
> Is there a way to schedule the other way (bottom up), or both ways?
> As a use case for bottom-up or some other heuristic:
> Currently, the first priority in the selection is given to the longest path, in some cases this may produce code with stalls at the end of the basic block. Whereas in the case of combined top-down + bottom-up scheduling we would end up having stalls in the middle of the basic block.
Why would that be better?