similar to: When to use auto instead of iterator/const_iterator?

Hello again, Sorry -- I think I found the problem somewhere else. I was a bit confused and missed the fact that adjustChainDeps() is called a few lines down and does just what I wanted :-) I would like to instead ask another question: Why is I->isCtrl() used in code like // Iterate over chain dependencies only. for (SUnit::const_succ_iterator I = SUb->Succs.begin(), E =

Hi, Thank you for the reply. >It looks to me like we can choose any subset of edges here and be correct. We're basically trying to prune/pinch the DAG edges here. They can easily blow up with AA sched. I would guess that isCtrl() edges are good ones to bypass because they could be a low-latecy edges, whereas true data dependencies from a load are expected to be >higher latency, so they

Hi, Can anyone help me to understand the ScheduleDAGInstrs::buildSchedGraph() method? I find the handling of AliasChain is disturbing since: 1. A new alias chain add deps to all possibly aliasing SUs, and then clears those lists. 2. When AliasChain is present, the addChainDependency() method is called, but the target hook areMemAccessesTriviallyDisjoint() called inside

Andy, Thanks for reply. I was able to trace the problem to the MI DAG dep constructor. See this: SU(0): %vreg1<def> = COPY %vreg10<kill>; IntRegs:%vreg1,%vreg10 # preds left : 0 # succs left : 0 # rdefs left : 1 Latency : 1 Depth : 0 Height : 0 SU(1): %vreg10<def> = LDriw %vreg9<kill>, 0;

Andy, I traced my problem to this point: In ScheduleDAGInstrs.cpp we have the following function: /// addVRegDefDeps - Add register output and data dependencies from this SUnit /// to instructions that occur later in the same scheduling region if they read /// from or write to the virtual register defined at OperIdx. /// /// TODO: Hoist loop induction variable increments. This has to be ///

Hi I have brought everything together in this email. The problem ======== Take the following DAG (arrow to predecessor): SetUp2 SetUp1 ^ ^ | | | | Destroy2---->PredSU <----SU ^ ^ ^ | | | | | | ----------- | ---------

On Thu, Aug 22, 2013 at 4:15 AM, Robert Lytton <robert at xmos.com> wrote: > > > Outstanding issues > ============ > > 1. Is it too aggressive in searching predecessors and successors? > Should the algorithm give up and assume the worst if the depth of > search reaches a predefined limit? > > 2. Should the initial search for 'SetUp1' and

Andy, et al., In ScheduleDAGInstrs::buildSchedGraph, the code for handling stores has this: if (!ExitSU.isPred(SU)) // Push store's up a bit to avoid them getting in between cmp // and branches. ExitSU.addPred(SDep(SU, SDep::Artificial)); This code does not seem to be in any way specific to compares; and in any case, at least on the PPC A2, scheduling stores in

On Jan 17, 2014, at 4:03 PM, Andrew Trick <atrick at apple.com> wrote: > > On Jan 17, 2014, at 3:54 PM, Hal Finkel <hfinkel at anl.gov> wrote: > >> Andy, et al., >> >> In ScheduleDAGInstrs::buildSchedGraph, the code for handling stores has this: >> >> if (!ExitSU.isPred(SU)) >> // Push store's up a bit to avoid them

Hi, On 06/18/2011 06:26 AM, Benjamin Müller wrote: > i created a Function Pass to retrieve the Control/Data Flow Graph from > a simple program, > now i would like to statically schedule the Instructions. Is this > possible by starting to modify the SelectionDAG Files ? > Or can i even build a "standalone" custom scheduler? > Thank you very much for any tipps. You

Hi there, i created a Function Pass to retrieve the Control/Data Flow Graph from a simple program, now i would like to statically schedule the Instructions. Is this possible by starting to modify the SelectionDAG Files ? Or can i even build a "standalone" custom scheduler? Thank you very much for any tipps. Ben

On Jun 13, 2012, at 10:49 AM, Sergei Larin <slarin at codeaurora.org> wrote: > So if this early exit is taken: > > // SSA defs do not have output/anti dependencies. > // The current operand is a def, so we have at least one. > if (llvm::next(MRI.def_begin(Reg)) == MRI.def_end()) > return; > > we do not ever get to this point: > >

[LLVMdev] tag added, sorry for duplicated message. Hi list, Could someone help me to understand the internal data dependecy structure used by the scheduler ? As far as I can see in /lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp, SUnit nodes are created to wrap SDNodes with scheduling related information and SDeps represent all kind of dependencies between them. Nevertheless, I cannot figure

On Tue, 4 Jul 2006, Fernando Magno Quintao Pereira wrote: > However, it does not remove all the critical edges. I am getting a very > weird dataflow graph (even without the Break Critical edges pass). The > dataflow generated by MachineFunction::dump() for the program below is > given here: > http://compilers.cs.ucla.edu/fernando/projects/soc/images/loop_no_crit2.pdf ... > The

Hi, I see that currently physical register uses marked as "undef" can still cause dependencies. Is this intentional? SU(9): %D5<def,undef> = LDrid %R0, 0, %R10<imp-def>, %R11<imp-def> # preds left : 0 # succs left : 11 # rdefs left : 0 Latency : 1 Depth : 0 Height : 0 Successors: ...

sorry, Just noticed that the diagrams have 'Destroy' & 'SetUp' the wrong way around! Robert ________________________________ From: llvmdev-bounces at cs.uiuc.edu [llvmdev-bounces at cs.uiuc.edu] on behalf of Robert Lytton [robert at xmos.com] Sent: 21 August 2013 18:34 To: llvmdev at cs.uiuc.edu Subject: Re: [LLVMdev] PrescheduleNodesWithMultipleUses() causing failure in

Hi Quentin, I have rerun the test case on a recent commit, so the numbers have changed. There are also now a few more basic blocks very small basic blocks in the function, and therefore there are some slight differences. I tried to go back to earlier commits, without success for some reason... This is however very similar, except that there becomes two COPYs back to sibling value after the loop.

> On Sep 21, 2016, at 2:23 PM, Daniel Berlin <dberlin at dberlin.org> wrote: > > > > // For all predecessors of this MBB, find the set of VarLocs that > // can be joined. > for (auto p : MBB.predecessors()) { > auto OL = OutLocs.find(p); > // Join is null in case of empty OutLocs from any of the pred. > if (OL == OutLocs.end()) >

Hi Jonas, Thanks for your patience. After spending some time looking at the additional output you gave me, I agree that your fix is the right one. I was worried that this problem may arise because we were spilling not real user, but in fact what I thought was the problem is an optimization we could do :). See my comments inlined for a few nitpicks before you commit. Thanks again, -Quentin On

Hi, I have reasoned through and believe the problem is with the PrescheduleNodesWithMultipleUses. Take the following DAG (arrow to predecessor): Destroy Destroy ^ ^ | | | | SetUp----->PredSU <-----SU ^ ^ ^ | | | | | | ----------- |