[PATCH] D124671: [AMDGPU] Do not raise wave priority beyond a specific number of VALU instructions.

[Jay Foad via Phabricator via llvm-commits]

foad added inline comments.


================
Comment at: llvm/lib/Target/AMDGPU/AMDGPUSetWavePriority.cpp:198-199
+    if (MachineInstr *LastVMEMLoad = MBBInfos[MBB].LastVMEMLoad) {
+      MBB->insertAfter(MachineBasicBlock::instr_iterator(LastVMEMLoad),
+                       Setprio);
+      continue;
----------------
kosarev wrote:
> arsenm wrote:
> > kosarev wrote:
> > > arsenm wrote:
> > > > Why not construct directly at the insert point?
> > > Well, the instruction we create here is not just an auxiliary value that we coincidentally happen to use in both the cases, if that's what you mean. That instruction must be spent in all cases and we do want it be the same instruction.
> > But you can construct it in the right place rather than constructing the instruction and then inserting after. You have the insert point you want, you can just construct it there? It's unusual to need insert/insertAfter
> I'm not sure I see how this answers the point. Granted that constructing the instruction at the points of insertion is possible, but as I said in this case we have reasons to create it in a single place.
I agree with Matt that it would be more normal to construct-and-insert at the same time, though I don't feel very strongly about it. I think I suggested before that you could pass the insertion point into BuildSetprioMI. In this case the insertion point would be something like `MBBInfos[MBB].LastVMEMLoad ? std::next(MBBInfos[MBB].LastVMEMLoad) : MBB->begin()`.


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  https://reviews.llvm.org/D124671/new/

https://reviews.llvm.org/D124671