From 9a31f0f398df8830161507a6dcf369961269c6cf Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Mon, 25 Oct 2010 20:45:32 +0000
Subject: [PATCH] Add simple counter to count no. of basic blocks without any
 line number information. At -O0, these basic block coule cause less than
 optimial debugging experience.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117307 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 2c0aeb7e014..69cdafc1b10 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -30,6 +30,7 @@
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Analysis/DebugInfo.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/CommandLine.h"
@@ -52,6 +53,8 @@ static cl::opt<bool> UnknownLocations("use-unknown-locations", cl::Hidden,
      cl::desc("Make an absense of debug location information explicit."),
      cl::init(false));
 
+STATISTIC(BlocksWithoutLineNo, "Number of blocks without any line number");
+
 namespace {
   const char *DWARFGroupName = "DWARF Emission";
   const char *DbgTimerName = "DWARF Debug Writer";
@@ -2770,12 +2773,37 @@ static DebugLoc FindFirstDebugLoc(const MachineFunction *MF) {
   return DebugLoc();
 }
 
+#ifndef NDEBUG
+/// CheckLineNumbers - Count basicblocks whose instructions do not have any
+/// line number information.
+static void CheckLineNumbers(const MachineFunction *MF) {
+  for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
+       I != E; ++I) {
+    bool FoundLineNo = false;
+    for (MachineBasicBlock::const_iterator II = I->begin(), IE = I->end();
+         II != IE; ++II) {
+      const MachineInstr *MI = II;
+      if (!MI->getDebugLoc().isUnknown()) {
+        FoundLineNo = true;
+        break;
+      }
+    }
+    if (!FoundLineNo)
+      ++BlocksWithoutLineNo;      
+  }
+}
+#endif
+
 /// beginFunction - Gather pre-function debug information.  Assumes being
 /// emitted immediately after the function entry point.
 void DwarfDebug::beginFunction(const MachineFunction *MF) {
   if (!MMI->hasDebugInfo()) return;
   if (!extractScopeInformation()) return;
 
+#ifndef NDEBUG
+  CheckLineNumbers(MF);
+#endif
+
   FunctionBeginSym = Asm->GetTempSymbol("func_begin",
                                         Asm->getFunctionNumber());
   // Assumes in correct section after the entry point.
-- 
2.11.0