[PATCH] D104161: [NFC] [DwarfEHPrepare] Add additional stats for EH

[Di Mo via Phabricator via llvm-commits]

modimo created this revision.
modimo added reviewers: wenlei, lebedev.ri, nikic.
Herald added subscribers: hoy, lxfind, hiraditya.
modimo requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

Stats added:

1. NumFunctionsProcessed: baseline to compare against
2. NumCleanupLandingPads/NumCleanupLandingPadsUnreachable: how many cleanup landing pads exist/how many were optimized as unreachable
3. NumNoUnwind: Number of functions with nounwind attribute

DwarfEHPrepare is always run a single time as part of `TargetPassConfig::addISelPasses()` which makes it an ideal place near the end of the pipeline to record this information.

Example output from clang built with exceptions:

"dwarfehprepare.NumCleanupLandingPads": 214916,
	"dwarfehprepare.NumFunctionsProcessed": 630099,
	"dwarfehprepare.NumNoUnwind": 299357,


https://reviews.llvm.org/D104161

Files:
  llvm/lib/CodeGen/DwarfEHPrepare.cpp


Index: llvm/lib/CodeGen/DwarfEHPrepare.cpp
===================================================================
--- llvm/lib/CodeGen/DwarfEHPrepare.cpp
+++ llvm/lib/CodeGen/DwarfEHPrepare.cpp
@@ -42,6 +42,11 @@
 #define DEBUG_TYPE "dwarfehprepare"
 
 STATISTIC(NumResumesLowered, "Number of resume calls lowered");
+STATISTIC(NumFunctionsProcessed, "Number of functions processed");
+STATISTIC(NumCleanupLandingPads, "Number of cleanup landing pads in program");
+STATISTIC(NumCleanupLandingPadsUnreachable,
+          "Number of cleanup landing pads found unreachable");
+STATISTIC(NumNoUnwind, "Number of functions with nounwind");
 
 namespace {
 
@@ -163,6 +168,9 @@
 bool DwarfEHPrepare::InsertUnwindResumeCalls() {
   SmallVector<ResumeInst *, 16> Resumes;
   SmallVector<LandingPadInst *, 16> CleanupLPads;
+  NumFunctionsProcessed++;
+  if (F.doesNotThrow())
+    NumNoUnwind++;
   for (BasicBlock &BB : F) {
     if (auto *RI = dyn_cast<ResumeInst>(BB.getTerminator()))
       Resumes.push_back(RI);
@@ -171,6 +179,8 @@
         CleanupLPads.push_back(LP);
   }
 
+  NumCleanupLandingPads += CleanupLPads.size();
+
   if (Resumes.empty())
     return false;
 
@@ -182,8 +192,18 @@
   LLVMContext &Ctx = F.getContext();
 
   size_t ResumesLeft = Resumes.size();
-  if (OptLevel != CodeGenOpt::None)
+  if (OptLevel != CodeGenOpt::None) {
     ResumesLeft = pruneUnreachableResumes(Resumes, CleanupLPads);
+#if LLVM_ENABLE_STATS
+    unsigned numRemainingLPs = 0;
+    for (BasicBlock &BB : F) {
+      if (auto *LP = BB.getLandingPadInst())
+        if (LP->isCleanup())
+          numRemainingLPs++;
+    }
+    NumCleanupLandingPadsUnreachable += CleanupLPads.size() - numRemainingLPs;
+#endif
+  }
 
   if (ResumesLeft == 0)
     return true; // We pruned them all.


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