[CodeExtractor] Erase debug intrinsics in outlined thunks (fix PR22900)

Variable updates within the outlined function are invisible to
debuggers. This could be improved by defining a DISubprogram for the
new function. For the moment, simply erase the debug intrinsics instead.

This fixes verifier failures about function-local metadata being used in
the wrong function, seen while testing the hot/cold splitting pass.

rdar://45142482

Differential Revision: https://reviews.llvm.org/D53267

llvm-svn: 344545

llvm/lib/Transforms/Utils/CodeExtractor.cpp

@@ -1286,6 +1286,19 @@ Function *CodeExtractor::extractCodeRegion() {
         }
     }
 
+  // Erase debug info intrinsics. Variable updates within the new function are
+  // invisible to debuggers. This could be improved by defining a DISubprogram
+  // for the new function.
+  for (BasicBlock &BB : *newFunction) {
+    auto BlockIt = BB.begin();
+    while (BlockIt != BB.end()) {
+      Instruction *Inst = &*BlockIt;
+      ++BlockIt;
+      if (isa<DbgInfoIntrinsic>(Inst))
+        Inst->eraseFromParent();
+    }
+  }
+
   LLVM_DEBUG(if (verifyFunction(*newFunction))
                  report_fatal_error("verifyFunction failed!"));
   return newFunction;