Inspired by seeing "MIPS" go by in the commits, I've gone ahead and
implemented a (codegen) target hook for __builtin_extend_pointer.
I'm also making it return a uint64_t instead of an unsigned word;  this
comports with typical usage (i.e. the one use I know of).

I don't know if any of the existing targets requires this hook to be
set (other than x86 and x86_64, which I know do not).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@97547 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TargetInfo.h b/lib/CodeGen/TargetInfo.h
index 58b7b79..b8a374c 100644
--- a/lib/CodeGen/TargetInfo.h
+++ b/lib/CodeGen/TargetInfo.h
@@ -44,6 +44,15 @@
     /// target-specific attributes for the given global.
     virtual void SetTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
                                      CodeGen::CodeGenModule &M) const { }
+
+    /// Controls whether __builtin_extend_pointer should sign-extend
+    /// pointers to uint64_t or zero-extend them (the default).  Has
+    /// no effect for targets:
+    ///   - that have 64-bit pointers, or
+    ///   - that cannot address through registers larger than pointers, or
+    ///   - that implicitly ignore/truncate the top bits when addressing
+    ///     through such registers.
+    virtual bool extendPointerWithSExt() const { return false; }
   };
 }