Re-apply the fix on DwarfEHPrepare and add a test

This patch re-introduces the fix in the commit llvm@66b0cebf7f736 by @yrnkrn

> In DwarfEHPrepare, after all passes are run, RewindFunction may be a dangling
>
> pointer to a dead function. To make sure it's valid, doFinalization nullptrs
> RewindFunction just like the constructor and so it will be found on next run.
>
> llvm-svn: 217737

It seems that the fix was not migrated to `DwarfEHPrepareLegacyPass`.

This patch also updates `llvm/test/CodeGen/X86/dwarf-eh-prepare.ll` to include `-run-twice` to exercise the cleanup. Without this patch `llvm-lit -v llvm/test/CodeGen/X86/dwarf-eh-prepare.ll` fails with

```
-- Testing: 1 tests, 1 workers --
FAIL: LLVM :: CodeGen/X86/dwarf-eh-prepare.ll (1 of 1)
******************** TEST 'LLVM :: CodeGen/X86/dwarf-eh-prepare.ll' FAILED ********************
Script:
--
: 'RUN: at line 1';   /home/arakaki/build/llvm-project/main/bin/opt -mtriple=x86_64-linux-gnu -dwarfehprepare -simplifycfg-require-and-preserve-domtree=1 -run-twice < /home/arakaki/repos/watch/llvm-project/llvm/test/CodeGen/X86/dwarf-eh-prepare.ll -S | /home/arakaki/build/llvm-project/main/bin/FileCheck /home/arakaki/repos/watch/llvm-project/llvm/test/CodeGen/X86/dwarf-eh-prepare.ll
--
Exit Code: 2

Command Output (stderr):
--
Referencing function in another module!
  call void @_Unwind_Resume(i8* %ehptr) #1
; ModuleID = '<stdin>'
void (i8*)* @_Unwind_Resume
; ModuleID = '<stdin>'
in function simple_cleanup_catch
LLVM ERROR: Broken function found, compilation aborted!
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /home/arakaki/build/llvm-project/main/bin/opt -mtriple=x86_64-linux-gnu -dwarfehprepare -simplifycfg-require-and-preserve-domtree=1 -run-twice -S
1.      Running pass 'Function Pass Manager' on module '<stdin>'.
2.      Running pass 'Module Verifier' on function '@simple_cleanup_catch'
 #0 0x000056121b570a2c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/arakaki/repos/watch/llvm-project/llvm/lib/Support/Unix/Signals.inc:569:0
 #1 0x000056121b56eb64 llvm::sys::RunSignalHandlers() /home/arakaki/repos/watch/llvm-project/llvm/lib/Support/Signals.cpp:97:0
 rust-lang#2 0x000056121b56f28e SignalHandler(int) /home/arakaki/repos/watch/llvm-project/llvm/lib/Support/Unix/Signals.inc:397:0
 rust-lang#3 0x00007fc7e9b22980 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12980)
 rust-lang#4 0x00007fc7e87d3fb7 raise /build/glibc-S7xCS9/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
 rust-lang#5 0x00007fc7e87d5921 abort /build/glibc-S7xCS9/glibc-2.27/stdlib/abort.c:81:0
 rust-lang#6 0x000056121b4e1386 llvm::raw_svector_ostream::raw_svector_ostream(llvm::SmallVectorImpl<char>&) /home/arakaki/repos/watch/llvm-project/llvm/include/llvm/Support/raw_ostream.h:674:0
 rust-lang#7 0x000056121b4e1386 llvm::report_fatal_error(llvm::Twine const&, bool) /home/arakaki/repos/watch/llvm-project/llvm/lib/Support/ErrorHandling.cpp:114:0
 rust-lang#8 0x000056121b4e1528 (/home/arakaki/build/llvm-project/main/bin/opt+0x29e3528)
 rust-lang#9 0x000056121adfd03f llvm::raw_ostream::operator<<(llvm::StringRef) /home/arakaki/repos/watch/llvm-project/llvm/include/llvm/Support/raw_ostream.h:218:0
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /home/arakaki/build/llvm-project/main/bin/FileCheck /home/arakaki/repos/watch/llvm-project/llvm/test/CodeGen/X86/dwarf-eh-prepare.ll

--

********************
********************
Failed Tests (1):
  LLVM :: CodeGen/X86/dwarf-eh-prepare.ll

Testing Time: 0.22s
  Failed: 1
```

Reviewed By: loladiro

Differential Revision: https://reviews.llvm.org/D110979

llvm/lib/CodeGen/DwarfEHPrepare.cpp

@@ -318,6 +318,11 @@ class DwarfEHPrepareLegacyPass : public FunctionPass {
     return prepareDwarfEH(OptLevel, RewindFunction, F, TLI, DT, TTI);
   }
 
+  bool doFinalization(Module &M) override {
+    RewindFunction = nullptr;
+    return false;
+  }
+
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<TargetPassConfig>();
     AU.addRequired<TargetTransformInfoWrapperPass>();

llvm/test/CodeGen/X86/dwarf-eh-prepare.ll

@@ -1,4 +1,4 @@
-; RUN: opt -mtriple=x86_64-linux-gnu -dwarfehprepare -simplifycfg-require-and-preserve-domtree=1 < %s -S | FileCheck %s
+; RUN: opt -mtriple=x86_64-linux-gnu -dwarfehprepare -simplifycfg-require-and-preserve-domtree=1 -run-twice < %s -S | FileCheck %s
 
 ; Check basic functionality of IR-to-IR DWARF EH preparation. This should
 ; eliminate resumes. This pass requires a TargetMachine, so we put it under X86