[PATCH] D26353: Add isHot{Cold}BB API to ProfileSummaryInfo

[Dehao Chen via llvm-commits]

danielcdh updated this revision to Diff 77408.
danielcdh added a comment.

update


https://reviews.llvm.org/D26353

Files:
  include/llvm/Analysis/ProfileSummaryInfo.h
  lib/Analysis/ProfileSummaryInfo.cpp


Index: lib/Analysis/ProfileSummaryInfo.cpp
===================================================================
--- lib/Analysis/ProfileSummaryInfo.cpp
+++ lib/Analysis/ProfileSummaryInfo.cpp
@@ -12,7 +12,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Analysis/BlockFrequencyInfo.h"
 #include "llvm/Analysis/ProfileSummaryInfo.h"
+#include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ProfileSummary.h"
@@ -121,6 +123,24 @@
   return ColdCountThreshold && C <= ColdCountThreshold.getValue();
 }
 
+bool ProfileSummaryInfo::isHotBB(const BasicBlock *B, BlockFrequencyInfo *BFI) {
+  auto Count = BFI->getBlockProfileCount(B);
+  if (Count && isHotCount(*Count))
+    return true;
+  // Use extractProfTotalWeight to get BB count.
+  // For Sample PGO, BFI may not provide accurate BB count due to errors
+  // magnified during sample count propagation. This serves as a backup plan
+  // to ensure all hot BB will not be missed.
+  // The query currently has false positives as branch instruction cloning does
+  // not update/scale branch weights. Unlike false negatives, this will not cause
+  // performance problem.
+  uint64_t TotalCount;
+  if (B->getTerminator()->extractProfTotalWeight(TotalCount) &&
+      isHotCount(TotalCount))
+    return true;
+  return false;
+}
+
 INITIALIZE_PASS(ProfileSummaryInfoWrapperPass, "profile-summary-info",
                 "Profile summary info", false, true)
 
Index: include/llvm/Analysis/ProfileSummaryInfo.h
===================================================================
--- include/llvm/Analysis/ProfileSummaryInfo.h
+++ include/llvm/Analysis/ProfileSummaryInfo.h
@@ -27,6 +27,8 @@
 #include <memory>
 
 namespace llvm {
+class BasicBlock;
+class BlockFrequencyInfo;
 class ProfileSummary;
 /// \brief Analysis providing profile information.
 ///
@@ -59,6 +61,8 @@
   bool isHotCount(uint64_t C);
   /// \brief Returns true if count \p C is considered cold.
   bool isColdCount(uint64_t C);
+  /// \brief Returns true if BasicBlock \p B is considered hot.
+  bool isHotBB(const BasicBlock *B, BlockFrequencyInfo *BFI);
 };
 
 /// An analysis pass based on legacy pass manager to deliver ProfileSummaryInfo.


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