Add a new function attribute, nonlazybind, which inhibits lazy-loading

optimizations when emitting calls to the function;  instead those calls may
use faster relocations which require the function to be immediately resolved
upon loading the dynamic object featuring the call.  This is useful when it
is known that the function will be called frequently and pervasively and
therefore there is no merit in delaying binding of the function.

Currently only implemented for x86-64, where it turns into a call through
the global offset table.

Patch by Dan Gohman, who assures me that he's going to add LangRef documentation
for this once it's committed.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133080 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Attributes.h

@@ -69,6 +69,9 @@ const Attributes Hotpatch    = 1<<29;     ///< Function should have special
                                           ///'hotpatch' sequence in prologue
 const Attributes UWTable     = 1<<30;     ///< Function must be in a unwind
                                           ///table
+const Attributes NonLazyBind = 1U<<31;    ///< Function is called early and/or
+                                          ///  often, so lazy binding isn't
+                                          ///  worthwhile.
 
 /// Note that uwtable is about the ABI or the user mandating an entry in the
 /// unwind table. The nounwind attribute is about an exception passing by the
@@ -90,7 +93,7 @@ const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
 const Attributes FunctionOnly = NoReturn | NoUnwind | ReadNone | ReadOnly |
   NoInline | AlwaysInline | OptimizeForSize | StackProtect | StackProtectReq |
   NoRedZone | NoImplicitFloat | Naked | InlineHint | StackAlignment |
-  Hotpatch | UWTable;
+  Hotpatch | UWTable | NonLazyBind;
 
 /// @brief Parameter attributes that do not apply to vararg call arguments.
 const Attributes VarArgsIncompatible = StructRet;