[gtk/half-float: 11/11] gsk: Add runtime checks for F16C

[Matthias Clasen <matthiasc src gnome org>]

commit f440b4851df0313b6faa7579ffaf01295e581d3d
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Apr 7 21:29:21 2021 -0400

    gsk: Add runtime checks for F16C
    
    Use an IFUNC resolver to determine whether we can use
    intrinsics for FP16 conversion. This requires the functions
    to be no longer inline.

 gsk/meson.build       |   1 +
 gsk/ngl/fp16.c        | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++
 gsk/ngl/fp16private.h |  84 ++------------------------------
 3 files changed, 134 insertions(+), 80 deletions(-)
---
diff --git a/gsk/meson.build b/gsk/meson.build
index 11be6a03f6..df3729d641 100644
--- a/gsk/meson.build
+++ b/gsk/meson.build
@@ -85,6 +85,7 @@ gsk_private_sources = files([
   'ngl/gskngltexturelibrary.c',
   'ngl/gskngluniformstate.c',
   'ngl/gskngltexturepool.c',
+  'ngl/fp16.c',
 ])
 
 gsk_public_headers = files([
diff --git a/gsk/ngl/fp16.c b/gsk/ngl/fp16.c
new file mode 100644
index 0000000000..22453ae210
--- /dev/null
+++ b/gsk/ngl/fp16.c
@@ -0,0 +1,129 @@
+/* fp16.c
+ *
+ * Copyright 2021 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#include <config.h>
+
+#include "fp16private.h"
+
+#ifdef HAVE_F16C
+#include <immintrin.h>
+#endif
+
+static inline guint
+as_uint (const float x)
+{
+  return *(guint*)&x;
+}
+
+static inline float
+as_float (const guint x)
+{
+  return *(float*)&x;
+}
+
+// IEEE-754 16-bit floating-point format (without infinity): 1-5-10
+
+static inline float
+half_to_float (const guint16 x)
+{
+  const guint e = (x&0x7C00)>>10; // exponent
+  const guint m = (x&0x03FF)<<13; // mantissa
+  const guint v = as_uint((float)m)>>23;
+  return as_float((x&0x8000)<<16 | (e!=0)*((e+112)<<23|m) | 
((e==0)&(m!=0))*((v-37)<<23|((m<<(150-v))&0x007FE000)));
+}
+
+static inline guint16
+float_to_half (const float x)
+{
+  const guint b = as_uint(x)+0x00001000; // round-to-nearest-even
+  const guint e = (b&0x7F800000)>>23; // exponent
+  const guint m = b&0x007FFFFF; // mantissa
+  return (b&0x80000000)>>16 | (e>112)*((((e-112)<<10)&0x7C00)|m>>13) | 
((e<113)&(e>101))*((((0x007FF000+m)>>(125-e))+1)>>1) | (e>143)*0x7FFF; // sign : normalized : denormalized : 
saturate
+}
+
+static void
+float_to_half4_c (const float f[4],
+                  guint16     h[4])
+{
+  h[0] = float_to_half (f[0]);
+  h[1] = float_to_half (f[1]);
+  h[2] = float_to_half (f[2]);
+  h[3] = float_to_half (f[3]);
+}
+
+static void
+half_to_float4_c (const guint16 h[4],
+                  float         f[4])
+{
+  f[0] = half_to_float (h[0]);
+  f[1] = half_to_float (h[1]);
+  f[2] = half_to_float (h[2]);
+  f[3] = half_to_float (h[3]);
+}
+
+#ifdef HAVE_F16C
+
+static void
+float_to_half4_f16c (const float f[4],
+                     guint16     h[4])
+{
+  __m128 s = _mm_loadu_ps (f);
+  __m128i i = _mm_cvtps_ph (s, 0);
+  _mm_storel_epi64 ((__m128i*)h, i);
+}
+
+static void
+half_to_float4_f16c (const guint16 h[4],
+                     float         f[4])
+{
+  __m128i i = _mm_loadl_epi64 ((__m128i_u const *)h);
+  __m128 s = _mm_cvtph_ps (i);
+  _mm_store_ps (f, s);
+}
+
+void float_to_half4 (const float f[4], guint16 h[4]) __attribute__((ifunc ("resolve_float_to_half4")));
+void half_to_float4 (const guint16 h[4], float f[4]) __attribute__((ifunc ("resolve_half_to_float4")));
+
+static void *
+resolve_float_to_half4 (void)
+{
+  __builtin_cpu_init ();
+  if (__builtin_cpu_supports ("f16c"))
+    return float_to_half4_f16c;
+  else
+    return float_to_half4_c;
+}
+
+static void *
+resolve_half_to_float4 (void)
+{
+  __builtin_cpu_init ();
+  if (__builtin_cpu_supports ("f16c"))
+    return half_to_float4_f16c;
+  else
+    return half_to_float4_c;
+}
+
+#else
+
+void float_to_half4 (const float f[4], guint16 h[4]) __attribute__((alias ("float_to_half4_c")));
+void half_to_float4 (const guint16 h[4], float f[4]) __attribute__((alias ("half_to_float4_c")));
+
+#endif  /* GTK_HAS_F16C */
diff --git a/gsk/ngl/fp16private.h b/gsk/ngl/fp16private.h
index 2bc9f84eea..d76f18a04f 100644
--- a/gsk/ngl/fp16private.h
+++ b/gsk/ngl/fp16private.h
@@ -21,13 +21,7 @@
 #ifndef __FP16_PRIVATE_H__
 #define __FP16_PRIVATE_H__
 
-#include <config.h>
 #include <glib.h>
-#include <graphene.h>
-
-#ifdef HAVE_F16C
-#include <immintrin.h>
-#endif
 
 G_BEGIN_DECLS
 
@@ -35,81 +29,11 @@ G_BEGIN_DECLS
 #define FP16_ONE ((guint16)15360)
 #define FP16_MINUS_ONE ((guint16)48128)
 
-#ifdef HAVE_F16C
-
-static inline void
-float_to_half4 (const float f[4],
-                guint16     h[4])
-{
-  __m128 s = _mm_loadu_ps (f);
-  __m128i i = _mm_cvtps_ph (s, 0);
-  _mm_storel_epi64 ((__m128i*)h, i);
-}
-
-static inline void
-half_to_float4 (const guint16 h[4],
-                float         f[4])
-{
-  __m128i i = _mm_loadl_epi64 ((__m128i_u const *)h);
-  __m128 s = _mm_cvtph_ps (i);
-  _mm_store_ps (f, s);
-}
-
-#else  /* GTK_HAS_F16C */
-
-static inline guint
-as_uint (const float x)
-{
-  return *(guint*)&x;
-}
-
-static inline float
-as_float (const guint x)
-{
-  return *(float*)&x;
-}
-
-// IEEE-754 16-bit floating-point format (without infinity): 1-5-10
-
-static inline float
-half_to_float (const guint16 x)
-{
-  const guint e = (x&0x7C00)>>10; // exponent
-  const guint m = (x&0x03FF)<<13; // mantissa
-  const guint v = as_uint((float)m)>>23;
-  return as_float((x&0x8000)<<16 | (e!=0)*((e+112)<<23|m) | 
((e==0)&(m!=0))*((v-37)<<23|((m<<(150-v))&0x007FE000)));
-}
-
-static inline guint16
-float_to_half (const float x)
-{
-  const guint b = as_uint(x)+0x00001000; // round-to-nearest-even
-  const guint e = (b&0x7F800000)>>23; // exponent
-  const guint m = b&0x007FFFFF; // mantissa
-  return (b&0x80000000)>>16 | (e>112)*((((e-112)<<10)&0x7C00)|m>>13) | 
((e<113)&(e>101))*((((0x007FF000+m)>>(125-e))+1)>>1) | (e>143)*0x7FFF; // sign : normalized : denormalized : 
saturate
-}
-
-static inline void
-float_to_half4 (const float f[4],
-                guint16     h[4])
-{
-  h[0] = float_to_half (f[0]);
-  h[1] = float_to_half (f[1]);
-  h[2] = float_to_half (f[2]);
-  h[3] = float_to_half (f[3]);
-}
-
-static inline void
-half_to_float4 (const guint16 h[4],
-                float         f[4])
-{
-  f[0] = half_to_float (h[0]);
-  f[1] = half_to_float (h[1]);
-  f[2] = half_to_float (h[2]);
-  f[3] = half_to_float (h[3]);
-}
+void float_to_half4 (const float f[4],
+                     guint16     h[4]);
 
-#endif  /* HAVE_F16C */
+void half_to_float4 (const guint16 h[4],
+                     float         f[4]);
 
 G_END_DECLS