From a25fbef08857ff0991877bb11e69a25943406915 Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <compnerd@compnerd.org>
Date: Wed, 29 Oct 2014 16:35:41 +0000
Subject: [PATCH] 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
---
 clang/include/clang/Basic/Builtins.def |  1 +
 clang/lib/CodeGen/CGBuiltin.cpp        |  8 ++++++++
 clang/lib/Headers/Intrin.h             |  4 ----
 clang/test/CodeGen/ms-intrinsics.c     | 15 ++++++++++++++-
 4 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/clang/include/clang/Basic/Builtins.def b/clang/include/clang/Basic/Builtins.def
index 72843f1fb6a6..dc668a161cb1 100644
--- a/clang/include/clang/Basic/Builtins.def
+++ b/clang/include/clang/Basic/Builtins.def
@@ -703,6 +703,7 @@ LANGBUILTIN(_InterlockedDecrement, "LiLiD*", "n", ALL_MS_LANGUAGES)
 LANGBUILTIN(_InterlockedExchangeAdd, "LiLiD*Li", "n", ALL_MS_LANGUAGES)
 LANGBUILTIN(_InterlockedExchangePointer, "v*v*D*v*", "n", ALL_MS_LANGUAGES)
 LANGBUILTIN(_InterlockedExchange, "LiLiD*Li", "n", ALL_MS_LANGUAGES)
+LANGBUILTIN(__readfsdword, "ULiULi", "n", ALL_MS_LANGUAGES)
 
 // C99 library functions
 // C99 stdlib.h
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index c4f92edc8a86..5cacfa12a47e 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 13e105ec1782..d5c334b2da16 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);
diff --git a/clang/test/CodeGen/ms-intrinsics.c b/clang/test/CodeGen/ms-intrinsics.c
index fb0f62c61c4b..c952c00be97c 100644
--- a/clang/test/CodeGen/ms-intrinsics.c
+++ b/clang/test/CodeGen/ms-intrinsics.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple i686--windows -fms-compatibility -Oz -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple i686--windows -fms-compatibility -Oz -emit-llvm %s -o - | FileCheck %s -check-prefix CHECK -check-prefix CHECK-I386
 // RUN: %clang_cc1 -triple thumbv7--windows -fms-compatibility -Oz -emit-llvm %s -o - | FileCheck %s
 
 void *test_InterlockedExchangePointer(void * volatile *Target, void *Value) {
@@ -36,3 +36,16 @@ long test_InterlockedExchange(long *Target, long Value) {
 // CHECK:   %[[EXCHANGE:[0-9]+]] = atomicrmw xchg i32* %Target, i32 %Value seq_cst
 // CHECK:   ret i32 %[[EXCHANGE:[0-9]+]]
 // CHECK: }
+
+#if defined(__i386__)
+long test__readfsdword(unsigned long Offset) {
+  return __readfsdword(Offset);
+}
+
+// CHECK-I386: define i32 @test__readfsdword(i32 %Offset){{.*}}{
+// CHECK-I386:   %0 = inttoptr i32 %Offset to i32 addrspace(257)*
+// CHECK-I386:   %1 = load volatile i32 addrspace(257)* %0, align 4
+// CHECK-I386:   ret i32 %1
+// CHECK-I386: }
+#endif
+