[PATCH] D120544: [AMDGPU] Omit unnecessary waitcnt before barriers

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/lib/Target/AMDGPU/AMDGPU.td:731
+  "true",
+  "Hardware supports backing off s_barrier if an exception occurs"
+>;
----------------
I don't understand what "backing off" means here


================
Comment at: llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp:1143
   if (MI.getOpcode() == AMDGPU::S_BARRIER &&
-      !ST->hasAutoWaitcntBeforeBarrier()) {
+      !ST->hasAutoWaitcntBeforeBarrier() && !ST->supportsBackOffBarrier()) {
     Wait = Wait.combined(AMDGPU::Waitcnt::allZero(ST->hasVscnt()));
----------------
Is this really a distinct feature if it's the same check as auto waitcnt?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D120544/new/

https://reviews.llvm.org/D120544