Mesa (master): gallivm: correct channel shift logic on big endian

[Roland Scheidegger]

Module: Mesa
Branch: master
Commit: 75cb6e36178b9474bbb59b76cbbcce2a67bf88d2
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=75cb6e36178b9474bbb59b76cbbcce2a67bf88d2

Author: Ray Strode <rstrode at redhat.com>
Date:   Wed Aug 23 16:32:42 2017 -0400

gallivm: correct channel shift logic on big endian

lp_build_fetch_rgba_soa fetches a texel from a texture.
Part of that process involves first gathering the element
together from memory into a packed format, and then breaking
out the individual color channels into separate, parallel
arrays.

The code fails to account for endianess when reading the packed
values.

This commit attempts to correct the problem by reversing the order
the packed values are read on big endian systems.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100613
Cc: "17.2" "17.1" <mesa-stable at lists.freedesktop.org>
Signed-off-by: Ray Strode <rstrode at redhat.com>
Reviewed-by: Roland Scheidegger <sroland at vmware.com>

---

 src/gallium/auxiliary/gallivm/lp_bld_format_soa.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/gallium/auxiliary/gallivm/lp_bld_format_soa.c b/src/gallium/auxiliary/gallivm/lp_bld_format_soa.c
index 98eb694c1f..22c19b10db 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_format_soa.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_format_soa.c
@@ -650,7 +650,13 @@ lp_build_fetch_rgba_soa(struct gallivm_state *gallivm,
          for (i = 0; i < format_desc->nr_channels; i++) {
             struct util_format_channel_description chan_desc = format_desc->channel[i];
             unsigned blockbits = type.width;
-            unsigned vec_nr = chan_desc.shift / type.width;
+            unsigned vec_nr;
+
+#ifdef PIPE_ARCH_BIG_ENDIAN
+            vec_nr = (format_desc->block.bits - (chan_desc.shift + chan_desc.size)) / type.width;
+#else
+            vec_nr = chan_desc.shift / type.width;
+#endif
             chan_desc.shift %= type.width;
 
             output[i] = lp_build_extract_soa_chan(&bld,