[PATCH v2 1/2] include: Fix ReadNoFence64 on i386.

[Jinoh Kang]

From: Jinoh Kang

64-bit volatile accesses are not atomic on i386.  Both
i686-w64-mingw32-gcc and x86 MSVC splits 64-bit loads into two
load/stores of a pair of 32-bit words.

Fix this by using FILD/FSTP pair, which is used to implement C11 atomics
by i686-w64-mingw32-gcc.

Fixes: f82b1c1fcf770a5d6fa02c3f286282be79a201b8
---
 include/winnt.h | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/include/winnt.h b/include/winnt.h
index 2547f841b7c..f93c27bb4a4 100644
--- a/include/winnt.h
+++ b/include/winnt.h
@@ -7122,7 +7122,15 @@ static FORCEINLINE LONG ReadNoFence( LONG const volatile *src )

static FORCEINLINE LONG64 ReadNoFence64( LONG64 const volatile *src )
 {
-    LONG64 value = __WINE_LOAD64_NO_FENCE( (__int64 const volatile *)src );
+    LONG64 value;
+#if defined(__i386__) && _MSC_VER < 1700
+    __asm {
+        fild qword ptr [src]
+        fistp qword ptr [value]
+    }
+#else
+    value = __WINE_LOAD64_NO_FENCE( (__int64 const volatile *)src );
+#endif
     return value;
 }

@@ -7315,7 +7323,11 @@ static FORCEINLINE LONG ReadNoFence( LONG const volatile *src )
 static FORCEINLINE LONG64 ReadNoFence64( LONG64 const volatile *src )
 {
     LONG64 value;
+#ifdef __i386__
+    __asm__ __volatile__( "fildq %1\n\tfistpq %0" : "=m" (value) : "m" (src) : "memory", "st" );
+#else
     __WINE_ATOMIC_LOAD_RELAXED( src, &value );
+#endif
     return value;
 }