msvcrt: Don't use fegetenv in nearbyint.

The fegetenv/feupdateenv functions are broken in msvcr120 and are causing unintentional SSE control word changes. Signed-off-by: Piotr Caban <piotr@codeweavers.com> Signed-off-by: Alexandre Julliard <julliard@winehq.org>

msvcrt: Don't use fegetenv in nearbyint.
5d9d195f · Piotr Caban · Alexandre Julliard · e617fe0b · 5d9d195f
Commit 5d9d195f authored Jan 31, 2022 by Piotr Caban Committed by Alexandre Julliard Feb 01, 2022
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math.c dlls/msvcrt/math.c +17 -5

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--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -6844,13 +6844,25 @@ double CDECL _yn(int n, double x)
 */
 double CDECL nearbyint(double x)
 {
-    fenv_t env;
+    BOOL update_cw, update_sw;
+    unsigned int cw, sw;

-    fegetenv(&env);
-    _control87(_MCW_EM, _MCW_EM);
+    _setfp(&cw, 0, &sw, 0);
+    update_cw = !(cw & _EM_INEXACT);
+    update_sw = !(sw & _SW_INEXACT);
+    if (update_cw)
+    {
+        cw |= _EM_INEXACT;
+        _setfp(&cw, _EM_INEXACT, NULL, 0);
+    }
    x = rint(x);
-    feclearexcept(FE_INEXACT);
-    feupdateenv(&env);
+    if (update_cw || update_sw)
+    {
+        sw = 0;
+        cw &= ~_EM_INEXACT;
+        _setfp(update_cw ? &cw : NULL, _EM_INEXACT,
+                update_sw ? &sw : NULL, _SW_INEXACT);
+    }
    return x;
 }