[PATCH] msvcrt: Don't set MXCSR register in __control87_2 if unchanged.

3 Jul 2020

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=27594
Signed-off-by: Myah Caron <qsniyg(a)protonmail.com>
---
I've only tested on x86 as I believe x64 is different enough to warrant a separate commit if the same issue is also present there.

Though I suspect the x87 control word might need the same treatment, I couldn't create a test case that displayed a requirement for this, so I've left it untouched.
---
 dlls/kernel32/tests/thread.c | 36 +++++++++++++++++++++++++-----
 dlls/msvcrt/math.c           | 43 ++++++++++++++++++++----------------
 2 files changed, 55 insertions(+), 24 deletions(-)

diff --git a/dlls/kernel32/tests/thread.c b/dlls/kernel32/tests/thread.c
index b476e44cfc..9b12b5043d 100644
--- a/dlls/kernel32/tests/thread.c
+++ b/dlls/kernel32/tests/thread.c
@@ -1829,6 +1829,19 @@ static inline unsigned long get_fpu_cw(void)
 #endif
 }

+static inline void set_fpu_cw(unsigned int cw, unsigned int sse)
+{
+#if defined(__i386__) || defined(__x86_64__)
+#ifdef _MSC_VER
+    __asm { fldcw [cw] }
+    __asm { ldmxcsr [sse] }
+#else
+    __asm__ volatile ("fldcw %0" : : "m" (cw));
+    __asm__ volatile ("ldmxcsr %0" : : "m" (sse));
+#endif
+#endif
+}
+
 static DWORD WINAPI fpu_thread(void *param)
 {
     struct fpu_thread_ctx *ctx = param;
@@ -1870,7 +1883,7 @@ static void test_thread_fpu_cw(void)
 {
     static const struct {
         unsigned int cw; unsigned long fpu_cw; unsigned long fpu_cw_broken;
-    } expected_cw[6] =
+    } expected_cw[7] =
     {
 #ifdef __i386__
         { _MCW_EM | _PC_53, MAKELONG( 0x27f, 0x1f80 ) },
@@ -1878,27 +1891,30 @@ static void test_thread_fpu_cw(void)
         { _EM_INEXACT | _RC_CHOP | _PC_24, MAKELONG( 0xc60, 0x7000 ), MAKELONG( 0xc60, 0x1f80 ) },
         { _MCW_EM | _PC_53, MAKELONG( 0x27f, 0x1f80 ) },
         { _EM_INEXACT | _RC_CHOP | _PC_24, MAKELONG( 0xc60, 0x7000 ), MAKELONG( 0xc60, 0x1f80 ) },
-        { _MCW_EM | _PC_53, MAKELONG( 0x27f, 0x1f80 ) }
+        { _MCW_EM | _PC_53, MAKELONG( 0x27f, 0x1f80 ) },
+        { _MCW_EM | _PC_24 | _RC_DOWN, MAKELONG( 0x47f, 0x3fa1 ) }
 #elif defined(__x86_64__)
         { _MCW_EM | _PC_64, MAKELONG( 0x27f, 0x1f80 ) },
         { _MCW_EM | _PC_64, MAKELONG( 0x27f, 0x1f80 ) },
         { _EM_INEXACT | _RC_CHOP | _PC_64, MAKELONG( 0x27f, 0x7000 ) },
         { _MCW_EM | _PC_64, MAKELONG( 0x27f, 0x1f80 ) },
         { _EM_INEXACT | _RC_CHOP | _PC_64, MAKELONG( 0x27f, 0x7000 ) },
-        { _MCW_EM | _PC_64, MAKELONG( 0x27f, 0x1f80 ) }
+        { _MCW_EM | _PC_64, MAKELONG( 0x27f, 0x1f80 ) },
+        { 0xdeadbeef, 0xdeadbeef }
 #elif defined(__aarch64__)
         { _MCW_EM | _PC_64, 0 },
         { _MCW_EM | _PC_64, 0 },
         { _EM_INEXACT | _RC_CHOP | _PC_64, 0xc08f00 },
         { _MCW_EM | _PC_64, 0 },
         { _EM_INEXACT | _RC_CHOP | _PC_64, 0xc08f00 },
-        { _MCW_EM | _PC_64, 0 }
+        { _MCW_EM | _PC_64, 0 },
+        { 0xdeadbeef, 0xdeadbeef }
 #else
         { 0xdeadbeef, 0xdeadbeef }
 #endif
     };
     unsigned int initial_cw, cw;
-    unsigned long fpu_cw;
+    unsigned long initial_fpu_cw, fpu_cw;

     fpu_cw = get_fpu_cw();
     initial_cw = _control87( 0, 0 );
@@ -1933,6 +1949,16 @@ static void test_thread_fpu_cw(void)
     fpu_cw = get_fpu_cw();
     ok(cw == expected_cw[5].cw, "expected %#x got %#x\n", expected_cw[5].cw, cw);
     ok(fpu_cw == expected_cw[5].fpu_cw, "expected %#lx got %#lx\n", expected_cw[5].fpu_cw, fpu_cw);
+
+#ifdef __i386__
+    initial_fpu_cw = get_fpu_cw();
+    set_fpu_cw(0x47f, 0x3fa1);
+    cw = _control87( _RC_DOWN, _MCW_RC );
+    fpu_cw = get_fpu_cw();
+    ok(cw == expected_cw[6].cw, "expected %#x got %#x\n", expected_cw[6].cw, cw);
+    ok(fpu_cw == expected_cw[6].fpu_cw, "expected %#lx got %#lx\n", expected_cw[6].fpu_cw, fpu_cw);
+    set_fpu_cw(initial_fpu_cw & 0xffff, (initial_fpu_cw >> 16) & 0xffff);
+#endif
 }

 static const char manifest_dep[] =
diff --git a/dlls/msvcrt/math.c b/dlls/msvcrt/math.c
index eae917076f..d11bd53acd 100644
--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -1107,6 +1107,7 @@ int CDECL __control87_2( unsigned int newval, unsigned int mask,
 #ifdef __GNUC__
     unsigned long fpword;
     unsigned int flags;
+    unsigned int old_flags;

     if (x86_cw)
     {
@@ -1196,29 +1197,33 @@ int CDECL __control87_2( unsigned int newval, unsigned int mask,
         TRACE( "sse2 flags=%08x newval=%08x mask=%08x\n", flags, newval, mask );
         if (mask)
         {
+            old_flags = flags;
             flags = (flags & ~mask) | (newval & mask);

-            /* Convert (masked) value back to fp word */
-            fpword = 0;
-            if (flags & MSVCRT__EM_INVALID)    fpword |= 0x80;
-            if (flags & MSVCRT__EM_DENORMAL)   fpword |= 0x100;
-            if (flags & MSVCRT__EM_ZERODIVIDE) fpword |= 0x200;
-            if (flags & MSVCRT__EM_OVERFLOW)   fpword |= 0x400;
-            if (flags & MSVCRT__EM_UNDERFLOW)  fpword |= 0x800;
-            if (flags & MSVCRT__EM_INEXACT)    fpword |= 0x1000;
-            switch (flags & MSVCRT__MCW_RC)
+            if (flags != old_flags)
             {
-            case MSVCRT__RC_UP|MSVCRT__RC_DOWN: fpword |= 0x6000; break;
-            case MSVCRT__RC_UP:                 fpword |= 0x4000; break;
-            case MSVCRT__RC_DOWN:               fpword |= 0x2000; break;
-            }
-            switch (flags & MSVCRT__MCW_DN)
-            {
-            case MSVCRT__DN_FLUSH_OPERANDS_SAVE_RESULTS: fpword |= 0x0040; break;
-            case MSVCRT__DN_SAVE_OPERANDS_FLUSH_RESULTS: fpword |= 0x8000; break;
-            case MSVCRT__DN_FLUSH:                       fpword |= 0x8040; break;
+                /* Convert (masked) value back to fp word */
+                fpword = 0;
+                if (flags & MSVCRT__EM_INVALID)    fpword |= 0x80;
+                if (flags & MSVCRT__EM_DENORMAL)   fpword |= 0x100;
+                if (flags & MSVCRT__EM_ZERODIVIDE) fpword |= 0x200;
+                if (flags & MSVCRT__EM_OVERFLOW)   fpword |= 0x400;
+                if (flags & MSVCRT__EM_UNDERFLOW)  fpword |= 0x800;
+                if (flags & MSVCRT__EM_INEXACT)    fpword |= 0x1000;
+                switch (flags & MSVCRT__MCW_RC)
+                {
+                case MSVCRT__RC_UP|MSVCRT__RC_DOWN: fpword |= 0x6000; break;
+                case MSVCRT__RC_UP:                 fpword |= 0x4000; break;
+                case MSVCRT__RC_DOWN:               fpword |= 0x2000; break;
+                }
+                switch (flags & MSVCRT__MCW_DN)
+                {
+                case MSVCRT__DN_FLUSH_OPERANDS_SAVE_RESULTS: fpword |= 0x0040; break;
+                case MSVCRT__DN_SAVE_OPERANDS_FLUSH_RESULTS: fpword |= 0x8000; break;
+                case MSVCRT__DN_FLUSH:                       fpword |= 0x8040; break;
+                }
+                __asm__ __volatile__( "ldmxcsr %0" : : "m" (fpword) );
             }
-            __asm__ __volatile__( "ldmxcsr %0" : : "m" (fpword) );
         }
         *sse2_cw = flags;
     }
--
2.26.2

    

Myah Caron

Myah Caron

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