Add -strip-nonlinetable-debuginfo capability

This adds a new function to DebugInfo.cpp that takes an llvm::Module
as input and removes all debug info metadata that is not directly
needed for line tables, thus effectively stripping all type and
variable information from the module.

The primary motivation for this feature was the bitcode work flow
(cf. http://lists.llvm.org/pipermail/llvm-dev/2016-June/100643.html
for more background). This is not wired up yet, but will be in
subsequent patches.  For testing, the new functionality is exposed to
opt with a -strip-nonlinetable-debuginfo option.

The secondary use-case (and one that works right now!) is as a
reduction pass in bugpoint. I added two new bugpoint options
(-disable-strip-debuginfo and -disable-strip-debug-types) to control
the new features. By default it will first attempt to remove all debug
information, then only the type info, and then proceed to hack at any
remaining MDNodes.

Thanks to Adrian Prantl for stewarding this patch!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285094 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 23 insertions, 0 deletions

diff --git a/tools/bugpoint/CrashDebugger.cpp b/tools/bugpoint/CrashDebugger.cpp
index a472fff0975..0cae0669477 100644
--- a/tools/bugpoint/CrashDebugger.cpp
+++ b/tools/bugpoint/CrashDebugger.cpp
@@ -19,6 +19,7 @@
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/CFG.h"
 #include "llvm/IR/Constants.h"
+#include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LegacyPassManager.h"
@@ -54,6 +55,12 @@ cl::opt<bool> DontReducePassList("disable-pass-list-reduction",
 cl::opt<bool> NoNamedMDRM("disable-namedmd-remove",
                           cl::desc("Do not remove global named metadata"),
                           cl::init(false));
+cl::opt<bool> NoStripDebugInfo("disable-strip-debuginfo",
+                               cl::desc("Do not strip debug info metadata"),
+                               cl::init(false));
+cl::opt<bool> NoStripDebugTypeInfo("disable-strip-debug-types",
+                               cl::desc("Do not strip debug type info metadata"),
+                               cl::init(false));
 cl::opt<bool> VerboseErrors("verbose-errors",
                             cl::desc("Print the output of crashing program"),
                             cl::init(false));
@@ -1123,6 +1130,22 @@ static Error DebugACrash(BugDriver &BD,
     if (Error E = ReduceInsts(BD, TestFn))
       return E;
 
+  // Attempt to strip debug info metadata.
+  auto stripMetadata = [&](std::function<bool(Module &)> strip) {
+    std::unique_ptr<Module> M = CloneModule(BD.getProgram());
+    strip(*M);
+    if (TestFn(BD, M.get()))
+      BD.setNewProgram(M.release());
+  };
+  if (!NoStripDebugInfo && !BugpointIsInterrupted) {
+    outs() << "\n*** Attempting to strip the debug info: ";
+    stripMetadata(StripDebugInfo);
+  }
+  if (!NoStripDebugTypeInfo && !BugpointIsInterrupted) {
+    outs() << "\n*** Attempting to strip the debug type info: ";
+    stripMetadata(stripNonLineTableDebugInfo);
+  }
+
   if (!NoNamedMDRM) {
     if (!BugpointIsInterrupted) {
       // Try to reduce the amount of global metadata (particularly debug info),