[Bug 81150] [SNB]Piglit spec_arb_shading_language_packing_execution_built-in-functions_fs-packSnorm4x8 fails

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Fri Aug 8 12:05:59 PDT 2014


--- Comment #3 from Neil Roberts <neil at linux.intel.com> ---
Glenn Kennard on IRC pointed out that setting bit 22 like that resembles a NaN
value getting munged when loading and storing through a floating-point
register. Indeed if I write a quick test that does fld and fst with 0x7f817f81
it comes out as 0x7fc17f81. I guess this works on 64-bit because that will use
SSE which apparently doesn't try to fix up NaNs on store. It also gets fixed on
the 32-bit SandyBridge build if I use -mfpmath=sse and -msse2.

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