[Debugify] Strip llvm.mir.debugify metadata

[asi-sc]

Summary

We don't strip llvm.mir.debugify metadata in llvm::stripDebugifyMetadata. This
may lead to incorrect number of lines and variables in the metadata when we run
debugify twice, e.g. -run-pass=mir-debugify,...,mir-strip-debug,...,mir-debugify.

[xiangzhangllvm]

LGTM (Seems we never directly run debugify twice before)

[xiangzhangllvm]

Let me accept it first, pls wait a little days to see if other reviewers has different opinions

llvm/lib/Transforms/Utils/Debugify.cpp

applyDebugify(Module &M,
   return collectDebugInfoMetadata(M, M.functions(), *DebugInfoBeforePass,
                                   "ModuleDebugify (original debuginfo)",
                                   NameOfWrappedPass);
 }
 
 bool llvm::stripDebugifyMetadata(Module &M) {
   bool Changed = false;
 
-  // Remove the llvm.debugify module-level named metadata.
+  // Remove the llvm.debugify and llvm.mir.debugify module-level named metadata.
   NamedMDNode *DebugifyMD = M.getNamedMetadata("llvm.debugify");
   if (DebugifyMD) {
     M.eraseNamedMetadata(DebugifyMD);
     Changed = true;
   }
 
+  if (auto *MIRDebugifyMD = M.getNamedMetadata("llvm.mir.debugify")) {
+    M.eraseNamedMetadata(MIRDebugifyMD);
+    Changed = true;
+  }
+
   // Strip out all debug intrinsics and supporting metadata (subprograms, types,
   // variables, etc).
   Changed |= StripDebugInfo(M);
 
   // Strip out the dead dbg.value prototype.
   Function *DbgValF = M.getFunction("llvm.dbg.value");
   if (DbgValF) {
     assert(DbgValF->isDeclaration() && DbgValF->use_empty() &&

llvm/test/CodeGen/Generic/MIRDebugify/locations-and-values.mir

--- |
   ; ALL: !llvm.dbg.cu = !{![[CU:[0-9]+]]}
   ; ALL: !llvm.debugify =
   ; ALL: !llvm.module.flags = !{![[VERSION:[0-9]+]]}
   ; ALL: ![[CU]] = distinct !DICompileUnit(
   ; ALL: ![[VERSION]] = !{i32 2, !"Debug Info Version", i32 3}
   ; VALUE: [[VAR1:![0-9]+]] = !DILocalVariable(name: "1"
   ; VALUE: [[VAR2:![0-9]+]] = !DILocalVariable(name: "2"
   ; STRIP-NOT: !llvm.debugify
-  ; STRIP: !llvm.mir.debugify
+  ; STRIP-NOT: !llvm.mir.debugify
 
 ...
 ---
 name:            test
 body:             |
   bb.1 (%ir-block.0):
     %0:_(s32) = IMPLICIT_DEF
     %1:_(s32) = IMPLICIT_DEF