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gsk, testsuite: Avoid undefined behaviour in float_to_half_one()

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If, for example, e == 0, it is undefined behaviour to compute an
expression involving an out-of-range shift by (125 - e), even if the
result is in fact irrelevant because it's going to be multiplied by 0.

This was already fixed for the memorytexture test in
commit 5d1b839 "testsuite: Fix another ubsan warning", so use the
implementation from that test everywhere. It's in the header as an
inline function to keep the linking of the relevant tests simple:
its only caller in production code is fp16.c, so there will be no
duplication outside the test suite.

Detected by running a subset of the test suite with
-Dsanitize=address,undefined on x86_64.

Signed-off-by: Simon McVittie <smcv@debian.org>
This commit is contained in:
Simon McVittie 2024-07-27 19:27:13 +01:00
parent d301d16aee
commit ad679187d3
4 changed files with 57 additions and 71 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
gsk/gl/fp16.c
View File

@ -45,15 +45,6 @@ half_to_float_one (const guint16 x)
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_one (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
}
void
float_to_half4_c (const float f[4],
guint16 h[4])

20
gsk/gl/fp16private.h
View File

@ -28,6 +28,26 @@ G_BEGIN_DECLS
#define FP16_ONE ((guint16)15360)
#define FP16_MINUS_ONE ((guint16)48128)
static inline guint16
float_to_half_one (const float x)
{
const guint b = *(guint*)&x+0x00001000; // round-to-nearest-even
const guint e = (b&0x7F800000)>>23; // exponent
const guint m = b&0x007FFFFF; // mantissa
guint n0 = 0;
guint n1 = 0;
guint n2 = 0;
if (e > 112)
n0 = (((e - 112) << 10) & 0x7C00) | m >> 13;
if (e < 113 && e > 101)
n1 = (((0x007FF000 + m) >> (125- e)) + 1) >> 1;
if (e > 143)
n2 = 0x7FFF;
return (b & 0x80000000) >> 16 | n0 | n1 | n2; // sign : normalized : denormalized : saturate
}
void float_to_half4 (const float f[4],
guint16 h[4]);

58
testsuite/gdk/memorytexture.c
View File

@ -2,6 +2,8 @@
#include <epoxy/gl.h>
#include "gsk/gl/fp16private.h"
#define N 10
static GdkGLContext *gl_context = NULL;
@ -59,7 +61,7 @@ as_float (const guint x)
// IEEE-754 16-bit floating-point format (without infinity): 1-5-10
//
static inline float
half_to_float (const guint16 x)
half_to_float_one (const guint16 x)
{
const guint e = (x&0x7C00)>>10; // exponent
const guint m = (x&0x03FF)<<13; // mantissa
@ -67,26 +69,6 @@ half_to_float (const guint16 x)
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 = *(guint*)&x+0x00001000; // round-to-nearest-even
const guint e = (b&0x7F800000)>>23; // exponent
const guint m = b&0x007FFFFF; // mantissa
guint n0 = 0;
guint n1 = 0;
guint n2 = 0;
if (e > 112)
n0 = (((e - 112) << 10) & 0x7C00) | m >> 13;
if (e < 113 && e > 101)
n1 = (((0x007FF000 + m) >> (125- e)) + 1) >> 1;
if (e > 143)
n2 = 0x7FFF;
return (b & 0x80000000) >> 16 | n0 | n1 | n2; // sign : normalized : denormalized : saturate
}
static gsize
gdk_memory_format_bytes_per_pixel (GdkMemoryFormat format)
{
@ -432,7 +414,7 @@ gdk_memory_format_pixel_print (GdkMemoryFormat format,
case GDK_MEMORY_R16G16B16_FLOAT:
{
const guint16 *data16 = (const guint16 *) data;
g_string_append_printf (string, "%f %f %f", half_to_float (data16[0]), half_to_float (data16[1]), half_to_float (data16[2]));
g_string_append_printf (string, "%f %f %f", half_to_float_one (data16[0]), half_to_float_one (data16[1]), half_to_float_one (data16[2]));
}
break;
@ -440,13 +422,13 @@ gdk_memory_format_pixel_print (GdkMemoryFormat format,
case GDK_MEMORY_R16G16B16A16_FLOAT_PREMULTIPLIED:
{
const guint16 *data16 = (const guint16 *) data;
g_string_append_printf (string, "%f %f %f %f", half_to_float (data16[0]), half_to_float (data16[1]), half_to_float (data16[2]), half_to_float (data16[3]));
g_string_append_printf (string, "%f %f %f %f", half_to_float_one (data16[0]), half_to_float_one (data16[1]), half_to_float_one (data16[2]), half_to_float_one (data16[3]));
}
break;
case GDK_MEMORY_A16_FLOAT:
{
const guint16 *data16 = (const guint16 *) data;
g_string_append_printf (string, "%f", half_to_float (data16[0]));
g_string_append_printf (string, "%f", half_to_float_one (data16[0]));
}
break;
@ -537,8 +519,8 @@ gdk_memory_format_pixel_equal (GdkMemoryFormat format,
guint i;
for (i = 0; i < gdk_memory_format_bytes_per_pixel (format) / sizeof (guint16); i++)
{
float f1 = half_to_float (((guint16 *) pixel1)[i]);
float f2 = half_to_float (((guint16 *) pixel2)[i]);
float f1 = half_to_float_one (((guint16 *) pixel1)[i]);
float f2 = half_to_float_one (((guint16 *) pixel2)[i]);
if (!G_APPROX_VALUE (f1, f2, accurate ? 1./65535 : 1./255))
return FALSE;
}
@ -774,9 +756,9 @@ texture_builder_set_pixel (TextureBuilder *builder,
case GDK_MEMORY_R16G16B16_FLOAT:
{
guint16 pixels[3] = {
float_to_half (color->red * color->alpha),
float_to_half (color->green * color->alpha),
float_to_half (color->blue * color->alpha)
float_to_half_one (color->red * color->alpha),
float_to_half_one (color->green * color->alpha),
float_to_half_one (color->blue * color->alpha)
};
memcpy (data, pixels, 3 * sizeof (guint16));
}
@ -784,10 +766,10 @@ texture_builder_set_pixel (TextureBuilder *builder,
case GDK_MEMORY_R16G16B16A16_FLOAT_PREMULTIPLIED:
{
guint16 pixels[4] = {
float_to_half (color->red * color->alpha),
float_to_half (color->green * color->alpha),
float_to_half (color->blue * color->alpha),
float_to_half (color->alpha)
float_to_half_one (color->red * color->alpha),
float_to_half_one (color->green * color->alpha),
float_to_half_one (color->blue * color->alpha),
float_to_half_one (color->alpha)
};
memcpy (data, pixels, 4 * sizeof (guint16));
}
@ -795,10 +777,10 @@ texture_builder_set_pixel (TextureBuilder *builder,
case GDK_MEMORY_R16G16B16A16_FLOAT:
{
guint16 pixels[4] = {
float_to_half (color->red),
float_to_half (color->green),
float_to_half (color->blue),
float_to_half (color->alpha)
float_to_half_one (color->red),
float_to_half_one (color->green),
float_to_half_one (color->blue),
float_to_half_one (color->alpha)
};
memcpy (data, pixels, 4 * sizeof (guint16));
}
@ -889,7 +871,7 @@ texture_builder_set_pixel (TextureBuilder *builder,
break;
case GDK_MEMORY_A16_FLOAT:
{
guint16 pixel = float_to_half (color->alpha);
guint16 pixel = float_to_half_one (color->alpha);
memcpy (data, &pixel, sizeof (guint16));
}
break;

41
testsuite/gsk/scaling.c
View File

@ -2,6 +2,8 @@
#define N 10
#include "gsk/gl/fp16private.h"
struct {
const char *name;
GskRenderer * (*create_func) (void);
@ -63,7 +65,7 @@ as_float (const guint x)
// IEEE-754 16-bit floating-point format (without infinity): 1-5-10
//
static inline float
half_to_float (const guint16 x)
half_to_float_one (const guint16 x)
{
const guint e = (x&0x7C00)>>10; // exponent
const guint m = (x&0x03FF)<<13; // mantissa
@ -71,15 +73,6 @@ half_to_float (const guint16 x)
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 = *(guint*)&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 gsize
gdk_memory_format_bytes_per_pixel (GdkMemoryFormat format)
{
@ -350,8 +343,8 @@ gdk_memory_format_pixel_equal (GdkMemoryFormat format,
guint i;
for (i = 0; i < gdk_memory_format_bytes_per_pixel (format) / sizeof (guint16); i++)
{
float f1 = half_to_float (((guint16 *) pixel1)[i]);
float f2 = half_to_float (((guint16 *) pixel2)[i]);
float f1 = half_to_float_one (((guint16 *) pixel1)[i]);
float f2 = half_to_float_one (((guint16 *) pixel2)[i]);
if (!G_APPROX_VALUE (f1, f2, accurate ? 1./65535 : 1./255))
return FALSE;
}
@ -567,9 +560,9 @@ texture_builder_set_pixel (TextureBuilder *builder,
case GDK_MEMORY_R16G16B16_FLOAT:
{
guint16 pixels[3] = {
float_to_half (color->red * color->alpha),
float_to_half (color->green * color->alpha),
float_to_half (color->blue * color->alpha)
float_to_half_one (color->red * color->alpha),
float_to_half_one (color->green * color->alpha),
float_to_half_one (color->blue * color->alpha)
};
memcpy (data, pixels, 3 * sizeof (guint16));
}
@ -577,10 +570,10 @@ texture_builder_set_pixel (TextureBuilder *builder,
case GDK_MEMORY_R16G16B16A16_FLOAT_PREMULTIPLIED:
{
guint16 pixels[4] = {
float_to_half (color->red * color->alpha),
float_to_half (color->green * color->alpha),
float_to_half (color->blue * color->alpha),
float_to_half (color->alpha)
float_to_half_one (color->red * color->alpha),
float_to_half_one (color->green * color->alpha),
float_to_half_one (color->blue * color->alpha),
float_to_half_one (color->alpha)
};
memcpy (data, pixels, 4 * sizeof (guint16));
}
@ -588,10 +581,10 @@ texture_builder_set_pixel (TextureBuilder *builder,
case GDK_MEMORY_R16G16B16A16_FLOAT:
{
guint16 pixels[4] = {
float_to_half (color->red),
float_to_half (color->green),
float_to_half (color->blue),
float_to_half (color->alpha)
float_to_half_one (color->red),
float_to_half_one (color->green),
float_to_half_one (color->blue),
float_to_half_one (color->alpha)
};
memcpy (data, pixels, 4 * sizeof (guint16));
}
@ -682,7 +675,7 @@ texture_builder_set_pixel (TextureBuilder *builder,
break;
case GDK_MEMORY_A16_FLOAT:
{
guint16 pixel = float_to_half (color->alpha);
guint16 pixel = float_to_half_one (color->alpha);
memcpy (data, &pixel, sizeof (guint16));
}
break;