search for: shouldignoreforpipelining

Hi all, I think there is a mistake in the machinepipeliner interface. In the TargetInstrInfo.h in the class PipelinerLoopInfo there is a function "bool shouldIgnoreForPipelining(const MachineInstr *MI)". The description says that if this function returns true for a given MachineInstr it will not be pipelined. However in reality it is not ignored and is being considered for pipelining. I implemented this function in my own backend, and put an instruction there tha...

...I’m missing? J.B. Nagurne Code Generation Texas Instruments From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Jinsong Ji via llvm-dev Sent: Tuesday, June 2, 2020 2:58 PM To: Sander Cc: llvm-dev at lists.llvm.org Subject: [EXTERNAL] Re: [llvm-dev] Machinepipeliner interface. shouldIgnoreForPipelining, actually not ignoring. Hi Sander: It may be confusing, but it is not a bug. And you are right, if you are using the in-tree machinepipeliner, it won't have any effects, because there is NO In tree reference of this API at all. You can see the comments when James introduced this API in http...

...> > > > *From:* James Molloy [mailto:jmolloy at google.com] > *Sent:* Monday, September 7, 2020 1:49 AM > *To:* Nagurne, James > *Cc:* Jinsong Ji; llvm-dev at lists.llvm.org; Sander; Hendrik Greving > *Subject:* Re: [EXTERNAL] RE: [llvm-dev] Machinepipeliner interface. > shouldIgnoreForPipelining, actually not ignoring. > > > > Hi James, > > > > Having not worked on this for circa one year I've gone and refreshed my > memory. > > > > We have a pretty capable implementation of swing modulo scheduling > downstream, distinct from the MachinePipelin...

...> > JB > > > > *From:* Jinsong Ji [mailto:jji at us.ibm.com] > *Sent:* Thursday, September 3, 2020 10:03 AM > *To:* Nagurne, James; jmolloy at google.com > *Cc:* llvm-dev at lists.llvm.org; Sander > *Subject:* [EXTERNAL] RE: [llvm-dev] Machinepipeliner interface. > shouldIgnoreForPipelining, actually not ignoring. > > > > As I mentioned before, > this API was introduced by James, mostly for his out-of-tree > implementations, > the in tree implementation NEVER implement it. > > If it is causing confusion, I think we have two choices: > 1. See whether James...

...e" and "ModuloScheduleExpander" classes, which we use downstream too (we actually have a minor variant, where we use predication for the prolog and epilog). However, the code that analyzes loops and determines a good schedule is completely custom. It is in this code that we use "shouldIgnoreForPipelining". All of this code is designed to go upstream. There is nothing stopping us putting it upstream (modulo some non-upstreamable features that may have crept in, but those can be removed). The major hurdle is that the target architecture is NOT upstream, and no existing upstream architecture loo...