msvcrt: Convert double (numerically) to UINT64 via INT64, fixing pow() on arm.

If converting a negative double to an UINT64, on arm it's clipped to zero instead of converted to its two's complement form (contrary to x86). This fixes cases like pow(2.0, -2.0) on arm/aarch64. Add similar casts to expf() too which seems to have a similar pattern, even if it's not known if that case can cause issues or not. In the original musl source, the converttoint() function returns a signed int32_t, doing the same double->signed->unsigned conversion, implicitly. Signed-off-by: Martin Storsjo <martin@martin.st> Signed-off-by: Piotr Caban <piotr@codeweavers.com> Signed-off-by: Alexandre Julliard <julliard@winehq.org>

msvcrt: Convert double (numerically) to UINT64 via INT64, fixing pow() on arm.
37b896db · Martin Storsjo · Alexandre Julliard · 057ecd41 · 37b896db
Commit 37b896db authored Jul 27, 2021 by Martin Storsjo Committed by Alexandre Julliard Jul 28, 2021
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math.c dlls/msvcrt/math.c +3 -3

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--- a/dlls/msvcrt/math.c
+++ b/dlls/msvcrt/math.c
@@ -1204,7 +1204,7 @@ float CDECL expf( float x )
       ideally ties-to-even rule is used, otherwise the magnitude of r
       can be bigger which gives larger approximation error.  */
    kd = __round(z);
-    ki = kd;
+    ki = (INT64)kd;
    r = z - kd;

    /* exp(x) = 2^(k/N) * 2^(r/N) ~= s * (C0*r^3 + C1*r^2 + C2*r + 1) */
@@ -1508,7 +1508,7 @@ static float powf_exp2(double xd, UINT32 sign_bias)

    /* N*x = k + r with r in [-1/2, 1/2] */
    kd = __round(xd); /* k */
-    ki = kd;
+    ki = (INT64)kd;
    r = xd - kd;

    /* exp2(x) = 2^(k/N) * 2^r ~= s * (C0*r^3 + C1*r^2 + C2*r + 1) */
@@ -3824,7 +3824,7 @@ static double pow_exp(double argx, double argy, double x, double xtail, UINT32 s
    /* x = ln2/N*k + r, with int k and r in [-ln2/2N, ln2/2N]. */
    z = invln2N * x;
    kd = __round(z);
-    ki = kd;
+    ki = (INT64)kd;
    r = x + kd * negln2hiN + kd * negln2loN;
    /* The code assumes 2^-200 < |xtail| < 2^-8/N. */
    r += xtail;