Introduce new linkage types linkonce_odr, weak_odr, common_odr

and extern_weak_odr.  These are the same as the non-odr versions,
except that they indicate that the global will only be overridden
by an *equivalent* global.  In C, a function with weak linkage can
be overridden by a function which behaves completely differently.
This means that IP passes have to skip weak functions, since any
deductions made from the function definition might be wrong, since
the definition could be replaced by something completely different
at link time.   This is not allowed in C++, thanks to the ODR
(One-Definition-Rule): if a function is replaced by another at
link-time, then the new function must be the same as the original
function.  If a language knows that a function or other global can
only be overridden by an equivalent global, it can give it the
weak_odr linkage type, and the optimizers will understand that it
is alright to make deductions based on the function body.  The
code generators on the other hand map weak and weak_odr linkage
to the same thing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66339 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 16 insertions, 8 deletions

diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 2ddfbe3..0fe6fc6 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -59,15 +59,19 @@ static GlobalValue::LinkageTypes GetDecodedLinkage(unsigned Val) {
   switch (Val) {
   default: // Map unknown/new linkages to external
   case 0: return GlobalValue::ExternalLinkage;
-  case 1: return GlobalValue::WeakLinkage;
+  case 1: return GlobalValue::WeakAnyLinkage;
   case 2: return GlobalValue::AppendingLinkage;
   case 3: return GlobalValue::InternalLinkage;
-  case 4: return GlobalValue::LinkOnceLinkage;
+  case 4: return GlobalValue::LinkOnceAnyLinkage;
   case 5: return GlobalValue::DLLImportLinkage;
   case 6: return GlobalValue::DLLExportLinkage;
-  case 7: return GlobalValue::ExternalWeakLinkage;
-  case 8: return GlobalValue::CommonLinkage;
+  case 7: return GlobalValue::ExternalWeakAnyLinkage;
+  case 8: return GlobalValue::CommonAnyLinkage;
   case 9: return GlobalValue::PrivateLinkage;
+  case 10: return GlobalValue::WeakODRLinkage;
+  case 11: return GlobalValue::LinkOnceODRLinkage;
+  case 12: return GlobalValue::ExternalWeakODRLinkage;
+  case 13: return GlobalValue::CommonODRLinkage;
   }
 }
 
diff --git a/lib/Bitcode/Writer/BitcodeWriter.cpp b/lib/Bitcode/Writer/BitcodeWriter.cpp
index 5633f0f..fefffbe 100644
--- a/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -276,15 +276,19 @@ static unsigned getEncodedLinkage(const GlobalValue *GV) {
   default: assert(0 && "Invalid linkage!");
   case GlobalValue::GhostLinkage:  // Map ghost linkage onto external.
   case GlobalValue::ExternalLinkage:     return 0;
-  case GlobalValue::WeakLinkage:         return 1;
+  case GlobalValue::WeakAnyLinkage:      return 1;
   case GlobalValue::AppendingLinkage:    return 2;
   case GlobalValue::InternalLinkage:     return 3;
-  case GlobalValue::LinkOnceLinkage:     return 4;
+  case GlobalValue::LinkOnceAnyLinkage:  return 4;
   case GlobalValue::DLLImportLinkage:    return 5;
   case GlobalValue::DLLExportLinkage:    return 6;
-  case GlobalValue::ExternalWeakLinkage: return 7;
-  case GlobalValue::CommonLinkage:       return 8;
+  case GlobalValue::ExternalWeakAnyLinkage: return 7;
+  case GlobalValue::CommonAnyLinkage:    return 8;
   case GlobalValue::PrivateLinkage:      return 9;
+  case GlobalValue::WeakODRLinkage:      return 10;
+  case GlobalValue::LinkOnceODRLinkage:  return 11;
+  case GlobalValue::ExternalWeakODRLinkage: return 12;
+  case GlobalValue::CommonODRLinkage:    return 13;
   }
 }