[PATCH] D16829: An implementation of Swing Modulo Scheduling

[Brendon Cahoon via Phabricator via llvm-commits]

bcahoon added a comment.

In https://reviews.llvm.org/D16829#638891, @lihan2011 wrote:

> when i use SMS.enterRegion(MBB, MBB->begin(), MBB->getFirstTerminator(), size); it occurs 
>  Assertion failed: VNI && "No value to read by operand"
>  but if use SMS.enterRegion(MBB, MBB->getFirstNonPHI(), MBB->getFirstTerminator(), size2); it has no error.
>  Am i use the wrong version of LLVM?


You do need pass MBB->begin() to enterRegion for the pipeliner to work correctly. It looks like you're using an older version of LLVM.  I believe this issue has been fixed with a commit that was made on Dec. 4 2015 to ScheduleDAGInstrs.cpp. If you're unable to use a newer version of LLVM, I'd suggest the following the following change to addVRegUseDeps in ScheduleDAGInstrs.cpp:

     // VNI will be valid because MachineOperand::readsReg() is checked by caller.
  -  assert(VNI && "No value to read by operand");
  -  MachineInstr *Def = LIS->getInstructionFromIndex(VNI->def);
  +  MachineInstr *Def = (VNI ? LIS->getInstructionFromIndex(VNI->def) : 0);
     // Phis and other noninstructions (after coalescing) have a NULL Def

Thanks,
Brendon


https://reviews.llvm.org/D16829