[PATCH] D84427: [llvm][NFC] refactor setBlockFrequency for clarity.

[Mircea Trofin via Phabricator via llvm-commits]

mtrofin created this revision.
mtrofin added a reviewer: yamauchi.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

The refactoring encapsulates frequency calculation in MachineBlockFrequencyInfo,
and renames the API to clarify its motivation. It should clarify
frequencies may not be reset 'freely' by users of the analysis, as the
API serves as a partial update to avoid a full analysis recomputation.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D84427

Files:
  llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
  llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
  llvm/lib/CodeGen/MachineSink.cpp


Index: llvm/lib/CodeGen/MachineSink.cpp
===================================================================
--- llvm/lib/CodeGen/MachineSink.cpp
+++ llvm/lib/CodeGen/MachineSink.cpp
@@ -347,11 +347,9 @@
                           << printMBBReference(*Pair.first) << " -- "
                           << printMBBReference(*NewSucc) << " -- "
                           << printMBBReference(*Pair.second) << '\n');
-        if (MBFI) {
-          auto NewSuccFreq = MBFI->getBlockFreq(Pair.first) *
-                             MBPI->getEdgeProbability(Pair.first, NewSucc);
-          MBFI->setBlockFreq(NewSucc, NewSuccFreq.getFrequency());
-        }
+        if (MBFI)
+          MBFI->onEdgeSplit(*Pair.first, *NewSucc, *MBPI);
+
         MadeChange = true;
         ++NumSplit;
       } else
Index: llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
===================================================================
--- llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
+++ llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
@@ -247,10 +247,15 @@
   return MBFI->isIrrLoopHeader(MBB);
 }
 
-void MachineBlockFrequencyInfo::setBlockFreq(const MachineBasicBlock *MBB,
-                                             uint64_t Freq) {
+void MachineBlockFrequencyInfo::onEdgeSplit(
+    const MachineBasicBlock &NewPredecessor,
+    const MachineBasicBlock &NewSuccessor,
+    const MachineBranchProbabilityInfo &MBPI) {
   assert(MBFI && "Expected analysis to be available");
-  MBFI->setBlockFreq(MBB, Freq);
+  auto NewSuccFreq = MBFI->getBlockFreq(&NewPredecessor) *
+                     MBPI.getEdgeProbability(&NewPredecessor, &NewSuccessor);
+
+  MBFI->setBlockFreq(&NewSuccessor, NewSuccFreq.getFrequency());
 }
 
 const MachineFunction *MachineBlockFrequencyInfo::getFunction() const {
Index: llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
===================================================================
--- llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
+++ llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
@@ -74,7 +74,11 @@
 
   bool isIrrLoopHeader(const MachineBasicBlock *MBB) const;
 
-  void setBlockFreq(const MachineBasicBlock *MBB, uint64_t Freq);
+  /// incrementally calculate block frequencies when we split edges, to avoid
+  /// full CFG traversal.
+  void onEdgeSplit(const MachineBasicBlock &NewPredecessor,
+                   const MachineBasicBlock &NewSuccessor,
+                   const MachineBranchProbabilityInfo &MBPI);
 
   const MachineFunction *getFunction() const;
   const MachineBranchProbabilityInfo *getMBPI() const;


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