[PATCH] D119475: [AMDGPU] Add scheduler pass to rematerialize trivial defs

Mon Feb 14 12:38:01 PST 2022

vangthao added inline comments.

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Comment at: llvm/lib/Target/AMDGPU/GCNSchedStrategy.cpp:799
+  // occupancy. Keep the modified live-in set from second check.
+  if (!ImprovedAfterSinkingLiveThrus) {
+    // Keep a list of newly rematerialized instructions so that we can easily
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rampitec wrote:
> vangthao wrote:
> > rampitec wrote:
> > > I do not think you really need a whole block above dealing with live-through estimations. First it is not guaranteed to help the RP if you sink a live-through. Second it is essentially the same as this block actually performing rematerialization, just less precise. Keep just rematerialization part.
> > If the live-through is increasing RP in this block then by rematerializing don't we decrease RP by the live-throughs that we rematerialized?
> I do not think LICM will hoist anything like that. Then even if so the code below will handle it as well.
The code below only checks for trivially rematerializable defs used in the high RP block. If the def is live-through and used in a low RP block then it will not be checked. This checks for that and sinks those defs to lower RP blocks so we can decrease live-through RP.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D119475/new/

https://reviews.llvm.org/D119475