[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

1 files changed, 8 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp b/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
index c836997..54e0a14 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 {