Escape subnormal values (#1953)

Currently we don't escape subnormal values when generating image data.
In sampler read tests, we use `!=` to check the two values even when it
is floating-point data, which requires the two values are bitwise equal.
However, a sampler might flush subnormal values, causing the test case
to fail.

In this patch, when generating random image data, we escape subnormal
values.

test_common/harness/imageHelpers.cpp

@@ -1128,13 +1128,15 @@ cl_ulong get_image_size_mb(image_descriptor const *imageInfo)
 uint64_t gRoundingStartValue = 0;
 
 
-void escape_inf_nan_values(char *data, size_t allocSize)
+void escape_inf_nan_subnormal_values(char *data, size_t allocSize)
 {
  // filter values with 8 not-quite-highest bits
  unsigned int *intPtr = (unsigned int *)data;
  for (size_t i = 0; i<allocSize>> 2; i++)
  {
  if ((intPtr[i] & 0x7F800000) == 0x7F800000) intPtr[i] ^= 0x40000000;
+ else if ((intPtr[i] & 0x7F800000) == 0)
+ intPtr[i] ^= 0x40000000;
  }
 
  // Ditto with half floats (16-bit numbers with the 5 not-quite-highest bits
@@ -1143,6 +1145,8 @@ void escape_inf_nan_values(char *data, size_t allocSize)
  for (size_t i = 0; i<allocSize>> 1; i++)
  {
  if ((shortPtr[i] & 0x7C00) == 0x7C00) shortPtr[i] ^= 0x4000;
+ else if ((shortPtr[i] & 0x7C00) == 0)
+ shortPtr[i] ^= 0x4000;
  }
 }
 
@@ -1221,7 +1225,7 @@ char *generate_random_image_data(image_descriptor *imageInfo,
 
  // Note: inf or nan float values would cause problems, although we don't
  // know this will actually be a float, so we just know what to look for
- escape_inf_nan_values(data, allocSize);
+ escape_inf_nan_subnormal_values(data, allocSize);
  return data;
  }
 
@@ -1233,7 +1237,7 @@ char *generate_random_image_data(image_descriptor *imageInfo,
 
  // Note: inf or nan float values would cause problems, although we don't
  // know this will actually be a float, so we just know what to look for
- escape_inf_nan_values(data, allocSize);
+ escape_inf_nan_subnormal_values(data, allocSize);
 
  if (/*!gTestMipmaps*/ imageInfo->num_mip_levels < 2)
  {