verify-di: Implement DebugInfoVerifier

Implement DebugInfoVerifier, which steals verification relying on
DebugInfoFinder from Verifier.

  - Adds LegacyDebugInfoVerifierPassPass, a ModulePass which wraps
    DebugInfoVerifier.  Uses -verify-di command-line flag.

  - Change verifyModule() to invoke DebugInfoVerifier as well as
    Verifier.

  - Add a call to createDebugInfoVerifierPass() wherever there was a
    call to createVerifierPass().

This implementation as a module pass should sidestep efficiency issues,
allowing us to turn debug info verification back on.

<rdar://problem/15500563>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206300 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/Passes.cpp

@@ -384,8 +384,10 @@ void TargetPassConfig::addIRPasses() {
 
   // Before running any passes, run the verifier to determine if the input
   // coming from the front-end and/or optimizer is valid.
-  if (!DisableVerify)
+  if (!DisableVerify) {
     addPass(createVerifierPass());
+    addPass(createDebugInfoVerifierPass());
+  }
 
   // Run loop strength reduction before anything else.
   if (getOptLevel() != CodeGenOpt::None && !DisableLSR) {
@@ -443,6 +445,12 @@ void TargetPassConfig::addCodeGenPrepare() {
 void TargetPassConfig::addISelPrepare() {
   addPreISel();
 
+  // Need to verify DebugInfo *before* creating the stack protector analysis.
+  // It's a function pass, and verifying between it and its users causes a
+  // crash.
+  if (!DisableVerify)
+    addPass(createDebugInfoVerifierPass());
+
   addPass(createStackProtectorPass(TM));
 
   if (PrintISelInput)