[llvm] 9ace311 - [DebugCounter] Add -print-debug-counter-queries option (#162827)

[via llvm-commits]

Author: Nikita Popov
Date: 2025-10-13T08:46:04Z
New Revision: 9ace31123d86220544f6d668e83ee3ff6f9f20db

URL: https://github.com/llvm/llvm-project/commit/9ace31123d86220544f6d668e83ee3ff6f9f20db
DIFF: https://github.com/llvm/llvm-project/commit/9ace31123d86220544f6d668e83ee3ff6f9f20db.diff

LOG: [DebugCounter] Add -print-debug-counter-queries option (#162827)

Add a `-print-debug-counter-queries` option which prints the current
value of the counter and whether it is executed/skipped each time it is
queried. This is useful when interleaving the output with the usual
transform debug output, in order to find the correct counter value to
use to hit a specific point in the transform.

Added: 
    

Modified: 
    llvm/include/llvm/Support/DebugCounter.h
    llvm/lib/Support/DebugCounter.cpp
    llvm/test/Other/debugcounter-dce.ll

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Support/DebugCounter.h b/llvm/include/llvm/Support/DebugCounter.h
index 48fc60035b189..39a08d499b67e 100644
--- a/llvm/include/llvm/Support/DebugCounter.h
+++ b/llvm/include/llvm/Support/DebugCounter.h
@@ -178,6 +178,7 @@ class DebugCounter {
     std::string Desc;
     SmallVector<Chunk> Chunks;
   };
+  bool handleCounterIncrement(CounterInfo &Info);
 
   DenseMap<unsigned, CounterInfo> Counters;
   CounterVector RegisteredCounters;
@@ -188,6 +189,8 @@ class DebugCounter {
 
   bool ShouldPrintCounter = false;
 
+  bool ShouldPrintCounterQueries = false;
+
   bool BreakOnLast = false;
 };
 

diff  --git a/llvm/lib/Support/DebugCounter.cpp b/llvm/lib/Support/DebugCounter.cpp
index 6b65720440f30..5ab1def43313b 100644
--- a/llvm/lib/Support/DebugCounter.cpp
+++ b/llvm/lib/Support/DebugCounter.cpp
@@ -136,6 +136,13 @@ struct DebugCounterOwner : DebugCounter {
       cl::location(this->ShouldPrintCounter),
       cl::init(false),
       cl::desc("Print out debug counter info after all counters accumulated")};
+  cl::opt<bool, true> PrintDebugCounterQueries{
+      "print-debug-counter-queries",
+      cl::Hidden,
+      cl::Optional,
+      cl::location(this->ShouldPrintCounterQueries),
+      cl::init(false),
+      cl::desc("Print out each query of an enabled debug counter")};
   cl::opt<bool, true> BreakOnLastCount{
       "debug-counter-break-on-last",
       cl::Hidden,
@@ -221,31 +228,40 @@ void DebugCounter::print(raw_ostream &OS) const {
   }
 }
 
+bool DebugCounter::handleCounterIncrement(CounterInfo &Info) {
+  int64_t CurrCount = Info.Count++;
+  uint64_t CurrIdx = Info.CurrChunkIdx;
+
+  if (Info.Chunks.empty())
+    return true;
+  if (CurrIdx >= Info.Chunks.size())
+    return false;
+
+  bool Res = Info.Chunks[CurrIdx].contains(CurrCount);
+  if (BreakOnLast && CurrIdx == (Info.Chunks.size() - 1) &&
+      CurrCount == Info.Chunks[CurrIdx].End) {
+    LLVM_BUILTIN_DEBUGTRAP;
+  }
+  if (CurrCount > Info.Chunks[CurrIdx].End) {
+    Info.CurrChunkIdx++;
+
+    /// Handle consecutive blocks.
+    if (Info.CurrChunkIdx < Info.Chunks.size() &&
+        CurrCount == Info.Chunks[Info.CurrChunkIdx].Begin)
+      return true;
+  }
+  return Res;
+}
+
 bool DebugCounter::shouldExecuteImpl(unsigned CounterName) {
   auto &Us = instance();
   auto Result = Us.Counters.find(CounterName);
   if (Result != Us.Counters.end()) {
     auto &CounterInfo = Result->second;
-    int64_t CurrCount = CounterInfo.Count++;
-    uint64_t CurrIdx = CounterInfo.CurrChunkIdx;
-
-    if (CounterInfo.Chunks.empty())
-      return true;
-    if (CurrIdx >= CounterInfo.Chunks.size())
-      return false;
-
-    bool Res = CounterInfo.Chunks[CurrIdx].contains(CurrCount);
-    if (Us.BreakOnLast && CurrIdx == (CounterInfo.Chunks.size() - 1) &&
-        CurrCount == CounterInfo.Chunks[CurrIdx].End) {
-      LLVM_BUILTIN_DEBUGTRAP;
-    }
-    if (CurrCount > CounterInfo.Chunks[CurrIdx].End) {
-      CounterInfo.CurrChunkIdx++;
-
-      /// Handle consecutive blocks.
-      if (CounterInfo.CurrChunkIdx < CounterInfo.Chunks.size() &&
-          CurrCount == CounterInfo.Chunks[CounterInfo.CurrChunkIdx].Begin)
-        return true;
+    bool Res = Us.handleCounterIncrement(CounterInfo);
+    if (Us.ShouldPrintCounterQueries && CounterInfo.IsSet) {
+      dbgs() << "DebugCounter " << Us.RegisteredCounters[CounterName] << "="
+             << (CounterInfo.Count - 1) << (Res ? " execute" : " skip") << "\n";
     }
     return Res;
   }

diff  --git a/llvm/test/Other/debugcounter-dce.ll b/llvm/test/Other/debugcounter-dce.ll
index 54d929f219aef..3b1dfb453593a 100644
--- a/llvm/test/Other/debugcounter-dce.ll
+++ b/llvm/test/Other/debugcounter-dce.ll
@@ -1,8 +1,16 @@
 ; REQUIRES: asserts
-; RUN: opt -passes=dce -S -debug-counter=dce-transform=1-2  < %s | FileCheck %s
+; RUN: opt -passes=dce -S -debug-counter=dce-transform=1-2  < %s | FileCheck %s --check-prefixes=CHECK,NO-PRINT
+; RUN: opt -passes=dce -S -debug-counter=dce-transform=1-2 -print-debug-counter-queries < %s 2>&1 | FileCheck %s --check-prefixes=CHECK,PRINT
 ;; Test that, with debug counters on, we will skip the first DCE opportunity, perform next 2,
 ;; and ignore all the others left.
 
+; NO-PRINT-NOT: DebugCounter
+; PRINT: DebugCounter dce-transform=0 skip
+; PRINT-NEXT: DebugCounter dce-transform=1 execute
+; PRINT-NEXT: DebugCounter dce-transform=2 execute
+; PRINT-NEXT: DebugCounter dce-transform=3 skip
+; PRINT-NEXT: DebugCounter dce-transform=4 skip
+
 ; CHECK-LABEL: @test
 ; CHECK-NEXT: %add1 = add i32 1, 2
 ; CHECK-NEXT: %sub1 = sub i32 %add1, 1