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List:       wine-devel
Subject:    [PATCH 1/4] msvcrt: Fix fmaf not to depend on rounding mode.
From:       Piotr Caban <piotr () codeweavers ! com>
Date:       2022-01-31 19:34:37
Message-ID: 48a66464-5b15-1dfe-908a-81dae5bea96d () codeweavers ! com
[Download RAW message or body]

Signed-off-by: Piotr Caban <piotr@codeweavers.com>
---
  dlls/msvcrt/math.c | 16 ++++++++++------
  1 file changed, 10 insertions(+), 6 deletions(-)


["0001-msvcrt-Fix-fmaf-not-to-depend-on-rounding-mode.txt" (text/x-patch)]

diff --git a/dlls/msvcrt/math.c b/dlls/msvcrt/math.c
index 9bb3e26570f..d03b4def801 100644
--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -5058,8 +5058,8 @@ double CDECL fma( double x, double y, double z )
 float CDECL fmaf( float x, float y, float z )
 {
     union { double f; UINT64 i; } u;
-    double xy, adjust;
-    int e;
+    double xy, err;
+    int e, neg;
 
     xy = (double)x * y;
     u.f = xy + z;
@@ -5083,11 +5083,15 @@ float CDECL fmaf( float x, float y, float z )
      * If result is inexact, and exactly halfway between two float values,
      * we need to adjust the low-order bit in the direction of the error.
      */
-    _controlfp(_RC_CHOP, _MCW_RC);
-    adjust = fp_barrier(xy + z);
-    _controlfp(_RC_NEAR, _MCW_RC);
-    if (u.f == adjust)
+    neg = u.i >> 63;
+    if (neg == (z > xy))
+        err = xy - u.f + z;
+    else
+        err = z - u.f + xy;
+    if (neg == (err < 0))
         u.i++;
+    else
+        u.i--;
     return u.f;
 }
 



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