Add initial support for debug counting

Summary:

We have support for bisection, and bugpoint can reduce testcases
often to a single pass. But that doesn't help reduce it to a single
transform by a single pass.  Which debug counting lets us do.

Debug counting lets you instrument a pass so that it only executes a
certain thing (rwhatever you want) after skipping it a certain time of
times, and then only does a certain number of executions before saying
"skip" again.

To make it concrete, for predicateinfo, if i instrument use renaming,
i can make it so it skips renaming the first N uses, renames the next
N, and then skips the rest.

This lets you narrow down a miscompilation to, often, a single
transformation, and then also debug it (by using the same command line
parameters).

Reviewers: chandlerc, davide, mehdi_amini

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D29998

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295593 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/CommandLine.h

@@ -343,6 +343,9 @@ class Option {
 
   virtual void printOptionValue(size_t GlobalWidth, bool Force) const = 0;
 
+  static void printHelpStr(StringRef HelpStr, size_t Indent,
+                           size_t FirstLineIndentedBy);
+
   virtual void getExtraOptionNames(SmallVectorImpl<StringRef> &) {}
 
   // addOccurrence - Wrapper around handleOccurrence that enforces Flags.

lib/Support/CMakeLists.txt

@@ -47,6 +47,7 @@ add_llvm_library(LLVMSupport
   CrashRecoveryContext.cpp
   DataExtractor.cpp
   Debug.cpp
+  DebugCounter.cpp
   DeltaAlgorithm.cpp
   DAGDeltaAlgorithm.cpp
   Dwarf.cpp

lib/Support/CommandLine.cpp

@@ -1404,8 +1404,8 @@ static StringRef getValueStr(const Option &O, StringRef DefaultMsg) {
 // Return the width of the option tag for printing...
 size_t alias::getOptionWidth() const { return ArgStr.size() + 6; }
 
-static void printHelpStr(StringRef HelpStr, size_t Indent,
-                         size_t FirstLineIndentedBy) {
+void Option::printHelpStr(StringRef HelpStr, size_t Indent,
+                                 size_t FirstLineIndentedBy) {
   std::pair<StringRef, StringRef> Split = HelpStr.split('\n');
   outs().indent(Indent - FirstLineIndentedBy) << " - " << Split.first << "\n";
   while (!Split.second.empty()) {
@@ -1448,7 +1448,7 @@ void basic_parser_impl::printOptionInfo(const Option &O,
   if (!ValName.empty())
     outs() << "=<" << getValueStr(O, ValName) << '>';
 
-  printHelpStr(O.HelpStr, GlobalWidth, getOptionWidth(O));
+  Option::printHelpStr(O.HelpStr, GlobalWidth, getOptionWidth(O));
 }
 
 void basic_parser_impl::printOptionName(const Option &O,
@@ -1587,7 +1587,7 @@ void generic_parser_base::printOptionInfo(const Option &O,
                                           size_t GlobalWidth) const {
   if (O.hasArgStr()) {
     outs() << "  -" << O.ArgStr;
-    printHelpStr(O.HelpStr, GlobalWidth, O.ArgStr.size() + 6);
+    Option::printHelpStr(O.HelpStr, GlobalWidth, O.ArgStr.size() + 6);
 
     for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
       size_t NumSpaces = GlobalWidth - getOption(i).size() - 8;
@@ -1600,7 +1600,7 @@ void generic_parser_base::printOptionInfo(const Option &O,
     for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
       auto Option = getOption(i);
       outs() << "    -" << Option;
-      printHelpStr(getDescription(i), GlobalWidth, Option.size() + 8);
+      Option::printHelpStr(getDescription(i), GlobalWidth, Option.size() + 8);
     }
   }
 }