[llvm] 1e027b7 - [llvm][NFC] refactor setBlockFrequency for clarity.

[Mircea Trofin via llvm-commits]

Author: Mircea Trofin
Date: 2020-07-28T13:04:11-07:00
New Revision: 1e027b77f056fb50e50d9f743e21eb41151c32da

URL: https://github.com/llvm/llvm-project/commit/1e027b77f056fb50e50d9f743e21eb41151c32da
DIFF: https://github.com/llvm/llvm-project/commit/1e027b77f056fb50e50d9f743e21eb41151c32da.diff

LOG: [llvm][NFC] refactor setBlockFrequency for clarity.

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.

Differential Revision: https://reviews.llvm.org/D84427

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h b/llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
index 7ce11c784b08..6c442d3d07bd 100644
--- a/llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
+++ b/llvm/include/llvm/CodeGen/MachineBlockFrequencyInfo.h
@@ -74,7 +74,11 @@ class MachineBlockFrequencyInfo : public MachineFunctionPass {
 
   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;

diff  --git a/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp b/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
index c83699706014..54e0a14e0555 100644
--- a/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
+++ b/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
@@ -247,10 +247,15 @@ bool MachineBlockFrequencyInfo::isIrrLoopHeader(
   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 {

diff  --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 5f958bbc31b7..dfb88f6bf517 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -347,11 +347,9 @@ bool MachineSinking::runOnMachineFunction(MachineFunction &MF) {
                           << 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