llvm dev - Jan 2014 - [LLVMdev] How to update LiveInterval information of newly inserted machine basic block

On Jan 4, 2014, at 4:38 AM, Haishan <hndxvon at 163.com> wrote:
>  At 2014-01-04 06:11:38,"Jakob Stoklund Olesen" <stoklund at
2pi.dk> wrote:
> 
> On Jan 3, 2014, at 1:52 PM, Andrew Trick <atrick at apple.com> wrote:
> 
>> He really just wants to rerun LiveIntervals analysis, but LiveVariables
is no longer available. Would it work just to clear all the intervals rerun
LiveIntervals::computeVirtRegs after all the CFG transforms are complete?
> 
> Yes, I should think so.
> 
> /jakob
> 
> 
> Thank you very much for your talk.
> I think I could append more information about updating LiveIntervals.
> 1. It works well if I just use from step1 to step3, without step4.
> 2. In step4, I firstly use UnreachableBlockElim pass to delete OldMBB.
> Then, remove all intervals and recompute all the virtual registers'
LiveIntervals.
> 3. I debug source code in LiveRangeCalc.cpp and copy partial code shown
following.
> /// LiveRangeCalc.cpp
> ...
> #ifndef NDEBUG
>     if (MBB->pred_empty()) {
>       MBB->getParent()->verify();
>       llvm_unreachable("Use not jointly dominated by defs.");
>     }
> ...
> /// LiveRangeCalc.cpp
> This MBB is the first block of MachineFunction. That's to say, This MBB
doesn't have predecessor. It is reasonable?
> From debug information, this unreachable error is generated from recompute
a virtual register which isn't used or defined in this MBB. But this virtual
register, in NewMBB,  is defined in a machine instruction which is copied from
OldMBB.
> So I am puzzled. 
> Then, I do as Andy's suggestion, but it doesn't work, and it has
same error.
> Could you have any suggestion?
> Thank you very much again.
Incrementally updating the live intervals will be complicated. You may be able
to completely recompute them by clearing all VirtRegIntervals, then calling
computeVirtRegs.

-Andy

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At 2014-01-05 03:28:22,"Andrew Trick" <atrick at apple.com>
wrote:


On Jan 4, 2014, at 4:38 AM, Haishan <hndxvon at 163.com> wrote:


 At 2014-01-04 06:11:38,"Jakob Stoklund Olesen" <stoklund at
2pi.dk> wrote:


On Jan 3, 2014, at 1:52 PM, Andrew Trick <atrick at apple.com> wrote:


He really just wants to rerun LiveIntervals analysis, but LiveVariables is no
longer available. Would it work just to clear all the intervals rerun
LiveIntervals::computeVirtRegs after all the CFG transforms are complete?


Yes, I should think so.


/jakob



Thank you very much for your talk.
I think I could append more information about updating LiveIntervals.
1. It works well if I just use from step1 to step3, without step4.
2. In step4, I firstly use UnreachableBlockElim pass to delete OldMBB.
Then, remove all intervals and recompute all the virtual registers'
LiveIntervals.
3. I debug source code in LiveRangeCalc.cpp and copy partial code shown
following.
/// LiveRangeCalc.cpp
...
#ifndef NDEBUG
    if (MBB->pred_empty()) {
      MBB->getParent()->verify();
      llvm_unreachable("Use not jointly dominated by defs.");
    }
...
/// LiveRangeCalc.cpp
This MBB is the first block of MachineFunction. That's to say, This MBB
doesn't have predecessor. It is reasonable?
From debug information, this unreachable error is generated from recompute a
virtual register which isn't used or defined in this MBB. But this virtual
register, in NewMBB,  is defined in a machine instruction which is copied from
OldMBB.
So I am puzzled. 
Then, I do as Andy's suggestion, but it doesn't work, and it has same
error.
Could you have any suggestion?
Thank you very much again.


Incrementally updating the live intervals will be complicated. You may be able
to completely recompute them by clearing all VirtRegIntervals, then calling
computeVirtRegs.


-Andy


Hi, 
  Thank you very much for replying.
  I have some doubt about only using computeVirtRegs function to update
LiveInterval.
  There are two other functions like "computeRegMasks()
computeLiveInRegUnits()" in runOnMachineFunction of
LiveIntervalAnalysis.cpp.
  So, I think that these two functions maybe effect updating LiveInterval
information.
  What do you think of two functions?
  
  Thank you very much again.
  -Haishan

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On Jan 5, 2014, at 5:24 AM, Haishan <hndxvon at 163.com> wrote:
> 
> At 2014-01-05 03:28:22,"Andrew Trick" <atrick at apple.com>
wrote:
> 
> On Jan 4, 2014, at 4:38 AM, Haishan <hndxvon at 163.com> wrote:
> 
>>  At 2014-01-04 06:11:38,"Jakob Stoklund Olesen" <stoklund
at 2pi.dk> wrote:
>> 
>> On Jan 3, 2014, at 1:52 PM, Andrew Trick <atrick at apple.com>
wrote:
>> 
>>> He really just wants to rerun LiveIntervals analysis, but
LiveVariables is no longer available. Would it work just to clear all the
intervals rerun LiveIntervals::computeVirtRegs after all the CFG transforms are
complete?
>> 
>> Yes, I should think so.
>> 
>> /jakob
>> 
>> 
>> Thank you very much for your talk.
>> I think I could append more information about updating LiveIntervals.
>> 1. It works well if I just use from step1 to step3, without step4.
>> 2. In step4, I firstly use UnreachableBlockElim pass to delete OldMBB.
>> Then, remove all intervals and recompute all the virtual registers'
LiveIntervals.
>> 3. I debug source code in LiveRangeCalc.cpp and copy partial code shown
following.
>> /// LiveRangeCalc.cpp
>> ...
>> #ifndef NDEBUG
>>     if (MBB->pred_empty()) {
>>       MBB->getParent()->verify();
>>       llvm_unreachable("Use not jointly dominated by defs.");
>>     }
>> ...
>> /// LiveRangeCalc.cpp
>> This MBB is the first block of MachineFunction. That's to say, This
MBB doesn't have predecessor. It is reasonable?
>> From debug information, this unreachable error is generated from
recompute a virtual register which isn't used or defined in this MBB. But
this virtual register, in NewMBB,  is defined in a machine instruction which is
copied from OldMBB.
>> So I am puzzled. 
>> Then, I do as Andy's suggestion, but it doesn't work, and it
has same error.
>> Could you have any suggestion?
>> Thank you very much again.
> 
> Incrementally updating the live intervals will be complicated. You may be
able to completely recompute them by clearing all VirtRegIntervals, then calling
computeVirtRegs.
> 
> -Andy
> 
> Hi, 
>   Thank you very much for replying.
>   I have some doubt about only using computeVirtRegs function to update
LiveInterval.
>   There are two other functions like "computeRegMasks()
computeLiveInRegUnits()" in runOnMachineFunction of
LiveIntervalAnalysis.cpp.
>   So, I think that these two functions maybe effect updating LiveInterval
information.
>   What do you think of two functions?
Yes, the safest thing would be to effectively rerun the LiveIntervals pass.
After finishing your CFG changes, You could try:

  releaseMemory()
  VirtRegIntervals.resize(MRI->getNumVirtRegs());
  computeVirtRegs();
  computeRegMasks();
  computeLiveInRegUnits();

I haven't tried this myself, so you may need to experiment/debug.


-Andy
>   
>   Thank you very much again.
>   -Haishan
> 
> 
> 
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