CodeGen: add __readfsdword builtin

The Windows NT SDK uses __readfsdword and declares it as a compiler provided
builtin (#pragma intrinsic(__readfsword).  Because intrin.h is not referenced
by winnt.h, it is not possible to provide an out-of-line definition for the
intrinsic.  Provide a proper compiler builtin definition.

llvm-svn: 220859

2 files changed, 8 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index c4f92edc8a8..5cacfa12a47 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -1624,6 +1624,14 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
     RMWI->setVolatile(true);
     return RValue::get(RMWI);
   }
+  case Builtin::BI__readfsdword: {
+    Value *IntToPtr =
+      Builder.CreateIntToPtr(EmitScalarExpr(E->getArg(0)),
+                             llvm::PointerType::get(CGM.Int32Ty, 257));
+    LoadInst *Load =
+        Builder.CreateAlignedLoad(IntToPtr, /*Align=*/4, /*isVolatile=*/true);
+    return RValue::get(Load);
+  }
   }
 
   // If this is an alias for a lib function (e.g. __builtin_sin), emit
diff --git a/clang/lib/Headers/Intrin.h b/clang/lib/Headers/Intrin.h
index 13e105ec178..d5c334b2da1 100644
--- a/clang/lib/Headers/Intrin.h
+++ b/clang/lib/Headers/Intrin.h
@@ -861,10 +861,6 @@ static __inline__ unsigned char __attribute__((__always_inline__, __nodebug__))
 __readfsbyte(unsigned long __offset) {
   return *__ptr_to_addr_space(257, unsigned char, __offset);
 }
-static __inline__ unsigned long __attribute__((__always_inline__, __nodebug__))
-__readfsdword(unsigned long __offset) {
-  return *__ptr_to_addr_space(257, unsigned long, __offset);
-}
 static __inline__ unsigned __int64 __attribute__((__always_inline__, __nodebug__))
 __readfsqword(unsigned long __offset) {
   return *__ptr_to_addr_space(257, unsigned __int64, __offset);