From 12b244394c45b1fdc1532e83972b3a579ff3bf8f Mon Sep 17 00:00:00 2001
From: Corinna Vinschen <corinna@vinschen.de>
Date: Mon, 25 Aug 2014 19:47:44 +0000
Subject: [PATCH] 	* cygtls.cc (san::leave/x86_64): Implement. 	*
 cygtls.h (class tls_pathbuf): Move counter variables into a union. 	Add 64
 bit element _counters covering both counter variables to 	optimize save
 and restore operations. 	(class san/x86_64): Only store single 64 bit
 value. 	(san::san/x86_64): Implement. 	(san::leave/x86_64): Only
 declare here, as returns_twice function. 	Explain why. 	(class
 san/i686): Change type of _c_cnt and _w_cnt to uint32_t. 
 (__try/x86_64): Move definition of __sebastian after the first memory 
 barrier.  Drop __sebastian.setup call.

---
 winsup/cygwin/ChangeLog | 14 ++++++++++++++
 winsup/cygwin/cygtls.cc |  8 ++++++++
 winsup/cygwin/cygtls.h  | 36 +++++++++++++++++++-----------------
 3 files changed, 41 insertions(+), 17 deletions(-)

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index a7cba5538..a6ee9dd4e 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,17 @@
+2014-08-25  Corinna Vinschen  <corinna@vinschen.de>
+
+	* cygtls.cc (san::leave/x86_64): Implement.
+	* cygtls.h (class tls_pathbuf): Move counter variables into a union.
+	Add 64 bit element _counters covering both counter variables to
+	optimize save and restore operations.
+	(class san/x86_64): Only store single 64 bit value.
+	(san::san/x86_64): Implement.
+	(san::leave/x86_64): Only declare here, as returns_twice function.
+	Explain why.
+	(class san/i686): Change type of _c_cnt and _w_cnt to uint32_t.
+	(__try/x86_64): Move definition of __sebastian after the first memory
+	barrier.  Drop __sebastian.setup call.
+
 2014-08-25  Corinna Vinschen  <corinna@vinschen.de>
 
 	* cygtls.cc (_cygtls::remove): Revert previous patch.
diff --git a/winsup/cygwin/cygtls.cc b/winsup/cygwin/cygtls.cc
index 5cc9405eb..2eaae9437 100644
--- a/winsup/cygwin/cygtls.cc
+++ b/winsup/cygwin/cygtls.cc
@@ -200,3 +200,11 @@ _cygtls::remove (DWORD wait)
   cygheap->remove_tls (this, wait);
   remove_wq (wait);
 }
+
+#ifdef __x86_64__
+void san::leave ()
+{
+  /* Restore tls_pathbuf counters in case of error. */
+  _my_tls.locals.pathbufs._counters = _cnt;
+}
+#endif
diff --git a/winsup/cygwin/cygtls.h b/winsup/cygwin/cygtls.h
index 3c19ab369..f09444e07 100644
--- a/winsup/cygwin/cygtls.h
+++ b/winsup/cygwin/cygtls.h
@@ -51,8 +51,15 @@ class tls_pathbuf
   /* Make sure that c_cnt and w_cnt are always the first two members of this
      class, and never change the size (32 bit), unless you also change the
      mov statements in sigbe! */
-  uint32_t c_cnt;
-  uint32_t w_cnt;
+  union
+    {
+      struct
+	{
+	  uint32_t c_cnt;
+	  uint32_t w_cnt;
+	};
+      uint64_t _counters;
+    };
   char  *c_buf[TP_NUM_C_BUFS];
   WCHAR *w_buf[TP_NUM_W_BUFS];
 
@@ -291,28 +298,24 @@ extern _cygtls *_sig_tls;
 #ifdef __x86_64__
 class san
 {
-  unsigned _c_cnt;
-  unsigned _w_cnt;
+  uint64_t _cnt;
 public:
-  void setup () __attribute__ ((always_inline))
+  san () __attribute__ ((always_inline))
   {
-    _c_cnt = _my_tls.locals.pathbufs.c_cnt;
-    _w_cnt = _my_tls.locals.pathbufs.w_cnt;
-  }
-  void leave () __attribute__ ((always_inline))
-  {
-    /* Restore tls_pathbuf counters in case of error. */
-    _my_tls.locals.pathbufs.c_cnt = _c_cnt;
-    _my_tls.locals.pathbufs.w_cnt = _w_cnt;
+    _cnt = _my_tls.locals.pathbufs._counters;
   }
+  /* This is the first thing called in the __except handler.  The attribute
+     "returns_twice" makes sure that GCC disregards any register value set
+     earlier in the function, so this call serves as a register barrier. */
+  void leave () __attribute__ ((returns_twice));
 };
 #else
 class san
 {
   san *_clemente;
   jmp_buf _context;
-  unsigned _c_cnt;
-  unsigned _w_cnt;
+  uint32_t _c_cnt;
+  uint32_t _w_cnt;
 public:
   int setup () __attribute__ ((always_inline))
   {
@@ -356,8 +359,8 @@ public:
 #define __try \
   { \
     __label__ __l_try, __l_except, __l_endtry; \
-    san __sebastian; \
     __mem_barrier; \
+    san __sebastian; \
     __asm__ goto ("\n" \
       "  .seh_handler _ZN9exception7myfaultEP17_EXCEPTION_RECORDPvP8_CONTEXTP19_DISPATCHER_CONTEXT, @except						\n" \
       "  .seh_handlerdata						\n" \
@@ -365,7 +368,6 @@ public:
       "  .rva %l[__l_try],%l[__l_endtry],%l[__l_except],%l[__l_except]	\n" \
       "  .seh_code							\n" \
       : : : : __l_try, __l_endtry, __l_except); \
-    __sebastian.setup (); \
     { \
       __l_try: \
 	__mem_barrier;
-- 
2.43.5