[PATCH] D20179: Fail early on unknown appending linkage variables

[Rafael Ávila de Espíndola via llvm-commits]

rafael created this revision.
rafael added a reviewer: dexonsmith.
rafael added a subscriber: llvm-commits.

In practice only a few well known appending linkage variables work.

Currently if codegen sees an unknown appending linkage variable it will just print it as a regular global. That is wrong as the symbol in the produced object file has different semantics as the one provided by the appending linkage.

This just errors early instead of producing a broken .o.

http://reviews.llvm.org/D20179

Files:
  lib/CodeGen/AsmPrinter/AsmPrinter.cpp
  test/CodeGen/X86/2007-08-13-AppendingLinkage.ll
  test/CodeGen/X86/AppendingLinkage.ll

Index: test/CodeGen/X86/AppendingLinkage.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/AppendingLinkage.ll
@@ -0,0 +1,4 @@
+; RUN: not llc < %s -march=x86 2>&1 | FileCheck %s
+
+; CHECK: unknown special variable
+ at foo = appending constant [1 x i32 ]zeroinitializer
Index: test/CodeGen/X86/2007-08-13-AppendingLinkage.ll
===================================================================
--- test/CodeGen/X86/2007-08-13-AppendingLinkage.ll
+++ /dev/null
@@ -1,12 +0,0 @@
-; RUN: llc < %s -march=x86 | not grep drectve
-; PR1607
-
-%hlvm_programs_element = type { i8*, i32 (i32, i8**)* }
- at hlvm_programs = appending constant [1 x %hlvm_programs_element]
-zeroinitializer
-
-define %hlvm_programs_element* @hlvm_get_programs() {
-entry:
-  ret %hlvm_programs_element* getelementptr([1 x %hlvm_programs_element], [1 x %hlvm_programs_element]*  
-                                            @hlvm_programs, i32 0, i32 0)
-}
Index: lib/CodeGen/AsmPrinter/AsmPrinter.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -318,17 +318,14 @@
       OutStreamer->EmitSymbolAttribute(GVSym, MCSA_Weak);
     }
     return;
-  case GlobalValue::AppendingLinkage:
-    // FIXME: appending linkage variables should go into a section of
-    // their name or something.  For now, just emit them as external.
   case GlobalValue::ExternalLinkage:
-    // If external or appending, declare as a global symbol.
-    // .globl _foo
+    // If external, declare as a global symbol: .globl _foo
     OutStreamer->EmitSymbolAttribute(GVSym, MCSA_Global);
     return;
   case GlobalValue::PrivateLinkage:
   case GlobalValue::InternalLinkage:
     return;
+  case GlobalValue::AppendingLinkage:
   case GlobalValue::AvailableExternallyLinkage:
   case GlobalValue::ExternalWeakLinkage:
     llvm_unreachable("Should never emit this");
@@ -1562,7 +1559,7 @@
     return true;
   }
 
-  return false;
+  report_fatal_error("unknown special variable");
 }
 
 /// EmitLLVMUsedList - For targets that define a MAI::UsedDirective, mark each


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