Revert F16C series (MR 6774)

This reverts commit 4fb2eddfdf9adafde2e6f94de23202ee44123d59.
This reverts commit 7a1deb16f8af4e0ae4ed64511cbfcc606087f0ee.
This reverts commit 2b6a17234376817e75d1f81edf5bd1b28eefb374.
This reverts commit 5af81393e419eaf086e4de2a1d149af78cd1f54d.
This reverts commit 87900afe5bbe90c5f3ad0921b28ae1c889029ada.

A couple of problems were discovered after this series was merged that
cause breakage in different configurations:

   (1) It seems that using -mf16c also enables AVX, leading to SIGILL on
   platforms that do not support AVX.
   (2) Since clang only warns about unknown flags, and as I understand
   it Meson's handling in cc.has_argument() is broken, the F16C code is
   wrongly enabled when clang is used, even for example on ARM, leading
   to a compilation error.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/3583
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6969>

1 files changed, 143 insertions, 0 deletions

diff --git a/src/gallium/auxiliary/util/u_half.h b/src/gallium/auxiliary/util/u_half.h
new file mode 100644
index 00000000000..bbcc843c310
--- /dev/null
+++ b/src/gallium/auxiliary/util/u_half.h
@@ -0,0 +1,143 @@
+/**************************************************************************
+ *
+ * Copyright 2010 Luca Barbieri
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+
+
+#ifndef U_HALF_H
+#define U_HALF_H
+
+#include "pipe/p_compiler.h"
+#include "util/u_math.h"
+#include "util/half_float.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * References for float <-> half conversions
+ *
+ *  http://fgiesen.wordpress.com/2012/03/28/half-to-float-done-quic/
+ *  https://gist.github.com/2156668
+ *  https://gist.github.com/2144712
+ */
+
+static inline uint16_t
+util_float_to_half(float f)
+{
+   return _mesa_float_to_half(f);
+}
+
+static inline uint16_t
+util_float_to_half_rtz(float f)
+{
+   uint32_t sign_mask  = 0x80000000;
+   uint32_t round_mask = ~0xfff;
+   uint32_t f32inf = 0xff << 23;
+   uint32_t f16inf = 0x1f << 23;
+   uint32_t sign;
+   union fi magic;
+   union fi f32;
+   uint16_t f16;
+
+   magic.ui = 0xf << 23;
+
+   f32.f = f;
+
+   /* Sign */
+   sign = f32.ui & sign_mask;
+   f32.ui ^= sign;
+
+   if (f32.ui == f32inf) {
+      /* Inf */
+      f16 = 0x7c00;
+   } else if (f32.ui > f32inf) {
+      /* NaN */
+      f16 = 0x7e00;
+   } else {
+      /* Number */
+      f32.ui &= round_mask;
+      f32.f  *= magic.f;
+      f32.ui -= round_mask;
+      /*
+       * XXX: The magic mul relies on denorms being available, otherwise
+       * all f16 denorms get flushed to zero - hence when this is used
+       * for tgsi_exec in softpipe we won't get f16 denorms.
+       */
+      /*
+       * Clamp to max finite value if overflowed.
+       * OpenGL has completely undefined rounding behavior for float to
+       * half-float conversions, and this matches what is mandated for float
+       * to fp11/fp10, which recommend round-to-nearest-finite too.
+       * (d3d10 is deeply unhappy about flushing such values to infinity, and
+       * while it also mandates round-to-zero it doesn't care nearly as much
+       * about that.)
+       */
+      if (f32.ui > f16inf)
+         f32.ui = f16inf - 1;
+
+      f16 = f32.ui >> 13;
+   }
+
+   /* Sign */
+   f16 |= sign >> 16;
+
+   return f16;
+}
+
+static inline float
+util_half_to_float(uint16_t f16)
+{
+   union fi infnan;
+   union fi magic;
+   union fi f32;
+
+   infnan.ui = 0x8f << 23;
+   infnan.f = 65536.0f;
+   magic.ui  = 0xef << 23;
+
+   /* Exponent / Mantissa */
+   f32.ui = (f16 & 0x7fff) << 13;
+
+   /* Adjust */
+   f32.f *= magic.f;
+   /* XXX: The magic mul relies on denorms being available */
+
+   /* Inf / NaN */
+   if (f32.f >= infnan.f)
+      f32.ui |= 0xff << 23;
+
+   /* Sign */
+   f32.ui |= (uint32_t)(f16 & 0x8000) << 16;
+
+   return f32.f;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* U_HALF_H */
+