similar to: Why not do machine instruction scheduling in SSA form?

A motivation for scheduling later is that the program representation is closer to the final instruction stream which makes the machine simulation more accurate. If you schedule too early you do not see the instructions produced by phi elimination and the two address fixup pass. LiveIntervals should work on MachineSSA form. If it doesn't you should file a bugzilla ticket with more details. -

Hello LLVM developers, I have a few questions regarding the passes that are run after instruction selection and before register allocation. I am writing a scheduling pass (modulo scheduling). Before I ask my questions, I will first try to explain the approach I am taking. - Currently, I am running the passes in the following order. (-debug-pass=Structure output) Remove unreachable machine

Hi (Jakob), in reference to the prior message below, I have the following follow-up questions, as I also need a scheduling pass prior to regalloc. I need to do this in order to set VLIW-flags, so that the RA is aware of several MI's per cycle with a redefined LiveRange::overlap-function. On a multiple-issue cycle, a register that gets killed can be reused by another MI - these live ranges do

Thanks for the suggestion. I tried your fix. It worked for my particular case, but then I got a following error: clang-3.5: /home/rail/projects/escala_llvm/trunk/llvm-or1k/lib/CodeGen/RegisterPressure.cpp:39: void decreaseSetPressure(std::vector<unsigned int>&, llvm::PSetIterator): Assertion `CurrSetPressure[*PSetI] >= Weight && "register pressure underflow"'

Apologies if my questions sound dumb. They are provided below. On Wed, Apr 27, 2016 at 2:43 PM, Krzysztof Parzyszek < kparzysz at codeaurora.org> wrote: > Are there any instructions (other than COPY) that use hardware > (allocatable) registers? > How do I find that out? > Could you show the instructions in the scheduling range? > How can I see instructions in the current

On May 24, 2011, at 8:22 AM, Jonas Paulsson wrote: > Hi (Jakob), > > in reference to the prior message below, I have the following follow-up questions, as I also need a scheduling pass > prior to regalloc. I need to do this in order to set VLIW-flags, so that the RA is aware of several MI's > per cycle with a redefined LiveRange::overlap-function. On a multiple-issue cycle, a

I was handed a makefile which is used to compile a library and was told to figure out why the compilation is failing. There is a lot of output and at this point I'm not sure what is important and what is not. I'm trying to solve this problem in small steps, so if asked I can certainly provide more information. The first error that I see during compilation is

On Aug 13, 2012, at 8:34 AM, Sergei Larin <slarin at codeaurora.org> wrote: > Andy, > > Yes, this is what Arnold has suggested also, and from this point it looks > like it should work, but it will require parsing the bundle every time we > care to know whether this is a real use or a conditional def. This might > become awkward... but I guess I should provide a better

There are uses of R0 all over the place, even though R0 is not marked as live-in to any of the blocks that use it. For example: BB#45: derived from LLVM BB %sw.bb54 Predecessors according to CFG: BB#43 BB#44 DBG_VALUE %vreg287, %noreg, !"base" %vreg203<def> = LWZ <fi#5>, 0; mem:LD4[%args] GPR:%vreg203 %vreg204<def> = ADDI %vreg203, 3;

Hi, I wonder when the preRASched pass is planned to be available? I wonder how one would best try to implement a pass in between RegCoalescer and RA. After RegCoalescer, the LiveVariables information seems broken (there are no Kills anywhere), and LiveVariables can't be rerun after SSA form is left. So, how could one rebuild LiveIntevals? For register allocation purposes - what would be the

> On Aug 30, 2017, at 1:43 PM, Matthias Braun <matze at braunis.de> wrote: > > That means you cannot use the code from RegisterPressure.{cpp|h} to compute this. The other liveness analysis we have in llvm codegen is LiveIntervals (LiveItnervalAnalysis) which gives you a list of liveness segments of a given vreg (the same representation is used in most linear scan allocators even

On 09/05/2013 18:25, Andrew Trick wrote: > > On May 9, 2013, at 4:02 AM, Fraser Cormack <fraser at codeplay.com > <mailto:fraser at codeplay.com>> wrote: > >> I have an instruction that takes no operands, and produces two >> results, in two consecutive cycles. >> >> I tried both of the following to my Schedule.td file: >> >>

Hi All, The description of ScheduleDAGMILive [1] says: ScheduleDAGMILive is an implementation of ScheduleDAGInstrs that schedules machine instructions while updating LiveIntervals and tracking regpressure. Does the live interval and register pressure part of ScheduleDAGMILive mean the subclass of ScheduleDAGMILive is a pre-RA scheduler? I assume the post-RA scheduler no need to take

I was reading about the order of optimizations in the code generation stage here: http://llvm.org/docs/CodeGenerator.html#the-high-level-design-of-the-code-generator This is the part that's interesting to me: 3. SSA-based Machine Code Optimizations<http://llvm.org/docs/CodeGenerator.html#ssa-based-machine-code-optimizations>— This optional stage consists of a series of machine-code

Hi, Thanks for your explanations! How is the big picture for supporting in-order VLIW architectures and the like though? I am asking because I am currently implementing instruction scheduling in our own backend for our custom Patmos processor, for which I need to support both branch delay slots and bundles, some restrictions regarding bundles. For the moment, I am quite happy with a simple

We have run an experiment in which we set all physical register limits to zero. The purpose of this experiment was estimating the potential impact of getting complete liveness info. The results of this experiment were better than the results that we got using the real physical limits (the total number of spills in CPU2006 was reduced), but the difference was not substantial. We took this as an

Andy, Jacob, I have ported Hexagon MI scheduler to use the new scheduler infrastructure, but one of my tests triggers an assert in LiveInterval update. On the surface it does not make much sense to me, so I wonder if this is something you readily recognize, before I try to prop it open... The assert is: lib/CodeGen/LiveInterval.cpp:266: llvm::LiveRange*

Hi, Matthias. >From the class hierarchy, ScheduleDAGMILive is also a ScheduleDAGMI. I am wondering if there will be any problem if we use subclass of ScheduleDAGMILive as post-RA scheduler? The best case is ScheduleDAGMILive just waste time on book-keeping register pressure, but I am not sure if we can still do those book-keeping after RA. Talk about post-RA scheduler, I see there is another

Fernando Magno Quintao Pereira wrote: > LiveVariables gives you something like liveness analysis: where each > variable is alive, that is, across each basic blocks, where it is defined, > and where it is killed. If I read this correctly, it means that at each instruction there's a list of live variables? I'm trying to figure out how to get at this information to build the

Hello All, I would like your help to learn how to traverse an LLVM DAG and perform some analysis. I know that llc can be used to view a DAG, but I would like to manipulate them. In particular I'm interested in the instruction selection and the scheduling DAGs. I have read the documentation about writing an analysis pass and I know how to traverse a basic block on a LLVM IR assembly file, but