[AsmPrinter] .addrsig_sym: remove isTransitiveUsedByMetadataOnly

[MaskRay]

Summary

With D135642 ignoring unregistered symbols, isTransitiveUsedByMetadataOnly added
by D101512 is no longer needed (the operation is potentially slow). There is a
.addrsig_sym directive for an only-used-by-metadata symbol but it does not
emit an entry.

[MaskRay]

Ping:)

[rnk]

lgtm

llvm/include/llvm/IR/Value.h

#include "llvm/IR/Value.def"
   }
 
   /// Return true if there is a value handle associated with this value.
   bool hasValueHandle() const { return HasValueHandle; }
 
   /// Return true if there is metadata referencing this value.
   bool isUsedByMetadata() const { return IsUsedByMD; }
 
-  // Return true if this value is only transitively referenced by metadata.
-  bool isTransitiveUsedByMetadataOnly() const;
-
 protected:
   /// Get the current metadata attachments for the given kind, if any.
   ///
   /// These functions require that the value have at most a single attachment
   /// of the given kind, and return \c nullptr if such an attachment is missing.
   /// @{
   MDNode *getMetadata(unsigned KindID) const;
   MDNode *getMetadata(StringRef Kind) const;

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

bool AsmPrinter::doFinalization(Module &M) {
   if (!InitTrampolineIntrinsic || InitTrampolineIntrinsic->use_empty())
     if (MCSection *S = MAI->getNonexecutableStackSection(OutContext))
       OutStreamer->switchSection(S);
 
   if (TM.Options.EmitAddrsig) {
     // Emit address-significance attributes for all globals.
     OutStreamer->emitAddrsig();
     for (const GlobalValue &GV : M.global_values()) {
-      if (!GV.use_empty() && !GV.isTransitiveUsedByMetadataOnly() &&
-          !GV.isThreadLocal() && !GV.hasDLLImportStorageClass() &&
-          !GV.getName().startswith("llvm.") && !GV.hasAtLeastLocalUnnamedAddr())
+      if (!GV.use_empty() && !GV.isThreadLocal() &&
+          !GV.hasDLLImportStorageClass() && !GV.getName().startswith("llvm.") &&
+          !GV.hasAtLeastLocalUnnamedAddr())
         OutStreamer->emitAddrsigSym(getSymbol(&GV));
     }
   }
 
   // Emit symbol partition specifications (ELF only).
   if (TM.getTargetTriple().isOSBinFormatELF()) {
     unsigned UniqueID = 0;
     for (const GlobalValue &GV : M.global_values()) {

llvm/lib/IR/Value.cpp

bool Value::isSwiftError() const {
   if (Arg)
     return Arg->hasSwiftErrorAttr();
   auto *Alloca = dyn_cast<AllocaInst>(this);
   if (!Alloca)
     return false;
   return Alloca->isSwiftError();
 }
 
-bool Value::isTransitiveUsedByMetadataOnly() const {
-  SmallVector<const User *, 32> WorkList(user_begin(), user_end());
-  SmallPtrSet<const User *, 32> Visited(user_begin(), user_end());
-  while (!WorkList.empty()) {
-    const User *U = WorkList.pop_back_val();
-    // If it is transitively used by a global value or a non-constant value,
-    // it's obviously not only used by metadata.
-    if (!isa<Constant>(U) || isa<GlobalValue>(U))
-      return false;
-    for (const User *UU : U->users())
-      if (Visited.insert(UU).second)
-        WorkList.push_back(UU);
-  }
-  return true;
-}
-
 //===----------------------------------------------------------------------===//
 //                             ValueHandleBase Class
 //===----------------------------------------------------------------------===//
 
 void ValueHandleBase::AddToExistingUseList(ValueHandleBase **List) {
   assert(List && "Handle list is null?");
 
   // Splice ourselves into the list.

llvm/test/CodeGen/X86/addrsig.ll

 ; RUN: llc < %s -mtriple=x86_64-unknown-linux | FileCheck --check-prefix=NO-ADDRSIG %s
 ; RUN: llc < %s -mtriple=x86_64-unknown-linux -addrsig | FileCheck %s
+; RUN: llc %s -filetype=obj -mtriple=x86_64-unknown-linux -addrsig -o %t
+; RUN: llvm-readobj --addrsig %t | FileCheck %s --check-prefix=SYM
 
 ; NO-ADDRSIG-NOT: .addrsig
 
+; SYM:      Addrsig [
+; SYM-NEXT:   Sym: f1
+; SYM-NEXT:   Sym: metadata_f2
+; SYM-NEXT:   Sym: g1
+; SYM-NEXT:   Sym: a1
+; SYM-NEXT:   Sym: i1
+; SYM-NEXT: ]
+
 ; CHECK: .addrsig
 
 ; CHECK: .addrsig_sym f1
 define void()* @f1() {
   %f1 = bitcast void()* ()* @f1 to i8*
   %f2 = bitcast void()* ()* @f2 to i8*
   %f3 = bitcast void()* @f3 to i8*
   %g1 = bitcast i32* @g1 to i8*
   %g2 = bitcast i32* @g2 to i8*
   %g3 = bitcast i32* @g3 to i8*
   %dllimport = bitcast i32* @dllimport to i8*
   %tls = bitcast i32* @tls to i8*
   %a1 = bitcast i32* @a1 to i8*
   %a2 = bitcast i32* @a2 to i8*
   %i1 = bitcast void()* @i1 to i8*
   %i2 = bitcast void()* @i2 to i8*
   call void @llvm.dbg.value(metadata i8* bitcast (void()* @metadata_f1 to i8*), metadata !5, metadata !DIExpression()), !dbg !7
   call void @llvm.dbg.value(metadata i8* bitcast (void()* @metadata_f2 to i8*), metadata !5, metadata !DIExpression()), !dbg !7
   call void @f4(i8* bitcast (void()* @metadata_f2 to i8*))
   unreachable
 }
 
 declare void @f4(i8*) unnamed_addr
 
-; CHECK-NOT: .addrsig_sym metadata_f1
+;; f1 is unreferenced, so this directive does not emit an entry.
+; CHECK: .addrsig_sym metadata_f1
 declare void @metadata_f1()
 
 ; CHECK: .addrsig_sym metadata_f2
 declare void @metadata_f2()
 
 ; CHECK-NOT: .addrsig_sym f2
 define internal void()* @f2() local_unnamed_addr {
   unreachable