[Bug 104395] [CTS] GTF-GL46.gtf32.GL3Tests.packed_pixels.packed_pixels tests fail on 32bit Mesa

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=104395

Kenneth Graunke <kenneth at whitecape.org> changed:

           What    |Removed                     |Added
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                 CC|                            |mattst88 at gmail.com

--- Comment #1 from Kenneth Graunke <kenneth at whitecape.org> ---
This basically boils down to:

   _mesa_lroundevenf(0.571428597f * 0xffffffffu)

returning wildly different results on 64-bit and 32-bit.

64-bit: result = 0x92492500
32-bit: result = 0x80000000

This happens even if I use the lrintf path directly instead of the SSE
intrinsics.

----------------------------------

How to arrive at this conclusion:

1. Simplify the test to do less work:
   a. Comment out all "formats" other than GL_RED
   b. Comment out all "types" other than GL_SHORT and GL_UNSIGNED_INT
3. Break in get_tex_rgba_uncompressed
   We should be doing a R16_SNORM -> R32_UNORM conversion here

4. Note the conversion to RGBA32_FLOAT for transfer ops
5. Observe that texgetimage.c:546 _mesa_format_convert has the same float
source data in both 32-bit and 64-bit builds, but produces different R32_UNORM
result data.

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