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<body><span class="vcard"><a class="email" href="mailto:kenneth@whitecape.org" title="Kenneth Graunke <kenneth@whitecape.org>"> <span class="fn">Kenneth Graunke</span></a>
</span> changed
<a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Compiler rejects chained assignments involving array dereferences"
href="https://bugs.freedesktop.org/show_bug.cgi?id=74026">bug 74026</a>
<br>
<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>ASSIGNED
</td>
<td>RESOLVED
</td>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>---
</td>
<td>FIXED
</td>
</tr></table>
<p>
<div>
<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Compiler rejects chained assignments involving array dereferences"
href="https://bugs.freedesktop.org/show_bug.cgi?id=74026#c2">Comment # 2</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Compiler rejects chained assignments involving array dereferences"
href="https://bugs.freedesktop.org/show_bug.cgi?id=74026">bug 74026</a>
from <span class="vcard"><a class="email" href="mailto:kenneth@whitecape.org" title="Kenneth Graunke <kenneth@whitecape.org>"> <span class="fn">Kenneth Graunke</span></a>
</span></b>
<pre>commit 44a86e2b4fca7c7cab243dfa62dc17f4379fc8e3
Author: Kenneth Graunke <<a href="mailto:kenneth@whitecape.org">kenneth@whitecape.org</a>>
Date: Fri Jan 24 10:47:49 2014 -0800
glsl: Fix chained assignments of vector channels.
Simple shaders such as:
void splat(vec2 v, float f) {
v[0] = v[1] = f;
}
failed to compile with the following error:
error: value of type vec2 cannot be assigned to variable of type float
First, we would process v[1] = f, and transform:
LHS: (expression float vector_extract (var_ref v) (constant int (1)))
RHS: (var_ref f)
into:
LHS: (var_ref v)
RHS: (expression vec2 vector_insert (var_ref v) (constant int (1))
(var_ref f))
Note that the LHS type is now vec2, not a float. This is surprising,
but not the real problem.
After emitting assignments, this ultimately becomes:
(declare (temporary) vec2 assignment_tmp)
(assign (xy)
(var_ref assignment_tmp)
(expression vec2 vector_insert (var_ref v) (constant int (1))
(var_ref f)))
(assign (xy) (var_ref v) (var_ref assignment_tmp))
We would then return (var_ref assignment_tmp) as the rvalue, which has
the wrong type---it should be float, but is instead a vec2.
To fix this, we simply return (vector_extract (var_ref assignment_temp)
<the appropriate channel>) to pull out the desired float value.
Fixes Piglit's chained-assignment-with-vector-constant-index.vert and
chained-assignment-with-vector-dynamic-index.vert tests.
Cc: <a href="mailto:mesa-stable@lists.freedesktop.org">mesa-stable@lists.freedesktop.org</a>
Bugzilla: <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Compiler rejects chained assignments involving array dereferences"
href="show_bug.cgi?id=74026">https://bugs.freedesktop.org/show_bug.cgi?id=74026</a>
Reported-by: Dan Ginsburg <<a href="mailto:dang@valvesoftware.com">dang@valvesoftware.com</a>>
Reviewed-by: Ian Romanick <<a href="mailto:ian.d.romanick@intel.com">ian.d.romanick@intel.com</a>>
Reviewed-by: Matt Turner <<a href="mailto:mattst88@gmail.com">mattst88@gmail.com</a>>
Signed-off-by: Kenneth Graunke <<a href="mailto:kenneth@whitecape.org">kenneth@whitecape.org</a>></pre>
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