[llvm] 8a168d2 - [LICM] Fix NumSunk statistic (NFC)

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2021-03-24T18:28:19+01:00
New Revision: 8a168d2d70678164004fca8de78e98bfb6e1272d

URL: https://github.com/llvm/llvm-project/commit/8a168d2d70678164004fca8de78e98bfb6e1272d
DIFF: https://github.com/llvm/llvm-project/commit/8a168d2d70678164004fca8de78e98bfb6e1272d.diff

LOG: [LICM] Fix NumSunk statistic (NFC)

LICM can sink instructions that have uses inside the loop, as
long as these uses are considered "free". However, if there were
only free uses inside the loop, and no uses outside the loop at
all, the instruction would still count towards the NumSunk
statistic. This resulted in a wild inflation of the NumSunk metric.
After this patch it drops down from 1141787 to 5852 on test-suite O3.

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/LICM.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 777e89e37e80..10426e600fca 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -1661,17 +1661,8 @@ static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT,
                  BlockFrequencyInfo *BFI, const Loop *CurLoop,
                  ICFLoopSafetyInfo *SafetyInfo, MemorySSAUpdater *MSSAU,
                  OptimizationRemarkEmitter *ORE) {
-  LLVM_DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n");
-  ORE->emit([&]() {
-    return OptimizationRemark(DEBUG_TYPE, "InstSunk", &I)
-           << "sinking " << ore::NV("Inst", &I);
-  });
   bool Changed = false;
-  if (isa<LoadInst>(I))
-    ++NumMovedLoads;
-  else if (isa<CallInst>(I))
-    ++NumMovedCalls;
-  ++NumSunk;
+  LLVM_DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n");
 
   // Iterate over users to be ready for actual sinking. Replace users via
   // unreachable blocks with undef and make all user PHIs trivially replaceable.
@@ -1723,6 +1714,16 @@ static bool sink(Instruction &I, LoopInfo *LI, DominatorTree *DT,
   if (VisitedUsers.empty())
     return Changed;
 
+  ORE->emit([&]() {
+    return OptimizationRemark(DEBUG_TYPE, "InstSunk", &I)
+           << "sinking " << ore::NV("Inst", &I);
+  });
+  if (isa<LoadInst>(I))
+    ++NumMovedLoads;
+  else if (isa<CallInst>(I))
+    ++NumMovedCalls;
+  ++NumSunk;
+
 #ifndef NDEBUG
   SmallVector<BasicBlock *, 32> ExitBlocks;
   CurLoop->getUniqueExitBlocks(ExitBlocks);