[PATCH] D145673: [llvm][CodeGen] Prevent endless loop when running the post-RA-sched pass.

[Xiaoqiang Xu via Phabricator via llvm-commits]

csstormq created this revision.
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Skip the stage that no functional units are required in ScoreboardHazardRecognizer::getHazardType. If not, this function will always return Hazard by default, leading to endless loop when running the post-RA-sched pass.

Although this problem only occurs in our downstream fork, it's completely general.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145673

Files:
  llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp


Index: llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp
===================================================================
--- llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp
+++ llvm/lib/CodeGen/ScoreboardHazardRecognizer.cpp
@@ -143,6 +143,13 @@
       }
 
       InstrStage::FuncUnits freeUnits = IS->getUnits();
+      if (!freeUnits) {
+        // No functional units are required by this stage, so cannot conflict.
+        // In addition, prevent endless loop when running the post-RA-sched
+        // pass.
+        continue;
+      }
+
       switch (IS->getReservationKind()) {
       case InstrStage::Required:
         // Required FUs conflict with both reserved and required ones


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