[PATCH] D41936: Allow dso_local on ifunc

[Rafael Avila de Espindola via Phabricator via llvm-commits]

espindola created this revision.
espindola added reviewers: sfertile, rnk.
Herald added a subscriber: hiraditya.

It was never fully disallowed. We were rejecting it in the asm parser, but not in the verifier.

Currently TargetMachine::shouldAssumeDSOLocal returns true for hidden ifuncs. I considered changing it and moving the check from the asm parser to the verifier.

The reason for deciding to allow it instead is that all linkers handle a direct reference just fine. They use the plt address as the address of the function. In fact doing that means that clang doesn't have the same bug as gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83782.

This patch then removes the check from the asm parser and updates the bitcode reader and writer.


https://reviews.llvm.org/D41936

Files:
  llvm/lib/AsmParser/LLParser.cpp
  llvm/lib/Bitcode/Reader/BitcodeReader.cpp
  llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
  llvm/test/Assembler/ifunc-dsolocal-daig.ll
  llvm/test/Assembler/ifunc-dsolocal.ll


Index: llvm/test/Assembler/ifunc-dsolocal.ll
===================================================================
--- llvm/test/Assembler/ifunc-dsolocal.ll
+++ llvm/test/Assembler/ifunc-dsolocal.ll
@@ -1,7 +1,7 @@
-; RUN: not llvm-as < %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
 
 @foo = dso_local ifunc i32 (i32), i64 ()* @foo_ifunc
-; CHECK: error: dso_local is invalid on ifunc
+; CHECK: @foo = dso_local ifunc i32 (i32), i64 ()* @foo_ifunc
 
 define internal i64 @foo_ifunc() {
 entry:
Index: llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -1302,14 +1302,15 @@
   // Emit the ifunc information.
   for (const GlobalIFunc &I : M.ifuncs()) {
     // IFUNC: [strtab offset, strtab size, ifunc type, address space, resolver
-    //         val#, linkage, visibility]
+    //         val#, linkage, visibility, DSO_Local]
     Vals.push_back(addToStrtab(I.getName()));
     Vals.push_back(I.getName().size());
     Vals.push_back(VE.getTypeID(I.getValueType()));
     Vals.push_back(I.getType()->getAddressSpace());
     Vals.push_back(VE.getValueID(I.getResolver()));
     Vals.push_back(getEncodedLinkage(I));
     Vals.push_back(getEncodedVisibility(I));
+    Vals.push_back(I.isDSOLocal());
     Stream.EmitRecord(bitc::MODULE_CODE_IFUNC, Vals);
     Vals.clear();
   }
Index: llvm/lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -3054,14 +3054,17 @@
       // FIXME: Change to an error if non-default in 4.0.
       NewGA->setVisibility(getDecodedVisibility(Record[VisInd]));
   }
-  if (OpNum != Record.size())
-    NewGA->setDLLStorageClass(getDecodedDLLStorageClass(Record[OpNum++]));
-  else
-    upgradeDLLImportExportLinkage(NewGA, Linkage);
-  if (OpNum != Record.size())
-    NewGA->setThreadLocalMode(getDecodedThreadLocalMode(Record[OpNum++]));
-  if (OpNum != Record.size())
-    NewGA->setUnnamedAddr(getDecodedUnnamedAddrType(Record[OpNum++]));
+  if (BitCode == bitc::MODULE_CODE_ALIAS ||
+      BitCode == bitc::MODULE_CODE_ALIAS_OLD) {
+    if (OpNum != Record.size())
+      NewGA->setDLLStorageClass(getDecodedDLLStorageClass(Record[OpNum++]));
+    else
+      upgradeDLLImportExportLinkage(NewGA, Linkage);
+    if (OpNum != Record.size())
+      NewGA->setThreadLocalMode(getDecodedThreadLocalMode(Record[OpNum++]));
+    if (OpNum != Record.size())
+      NewGA->setUnnamedAddr(getDecodedUnnamedAddrType(Record[OpNum++]));
+  }
   if (OpNum != Record.size())
     NewGA->setDSOLocal(getDecodedDSOLocal(Record[OpNum++]));
   ValueList.push_back(NewGA);
Index: llvm/lib/AsmParser/LLParser.cpp
===================================================================
--- llvm/lib/AsmParser/LLParser.cpp
+++ llvm/lib/AsmParser/LLParser.cpp
@@ -749,11 +749,6 @@
     return Error(NameLoc,
                  "symbol with local linkage must have default visibility");
 
-  if (DSOLocal && !IsAlias) {
-    return Error(NameLoc,
-                 "dso_local is invalid on ifunc");
-  }
-
   Type *Ty;
   LocTy ExplicitTypeLoc = Lex.getLoc();
   if (ParseType(Ty) ||


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