Mesa (master): i965: Make split_virtual_grfs() call compact_virtual_grfs() .

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: 27715c73ff84349466f62df0023863acd477f262
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=27715c73ff84349466f62df0023863acd477f262

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Sat Oct 15 03:18:36 2016 -0700

i965: Make split_virtual_grfs() call compact_virtual_grfs().

Post-splitting, VGRFs have a maximum size (MAX_VGRF_SIZE).  This is
required by the register allocator, as we have to create classes for
each size of VGRF.

We can (and do) allocate virtual registers larger than MAX_VGRF_SIZE,
but we must ensure that they are splittable.  split_virtual_grfs()
asserts that the post-splitting register size is in range.

Unfortunately, these trip for completely dead registers which are too
large - we only set split points for live registers.  So dead ones are
never split, and if they happened to be too large, they'd trip asserts.

To fix this, call compact_virtual_grfs() to eliminate dead registers
before splitting.

v2: Add a comment written by Iago.

Cc: mesa-stable at lists.freedesktop.org
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Iago Toral Quiroga <itoral at igalia.com>
Reviewed-by: Timothy Arceri <timothy.arceri at collabora.com>

---

 src/mesa/drivers/dri/i965/brw_fs.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 1c7a6e6..7738a47 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -1687,6 +1687,12 @@ fs_visitor::assign_gs_urb_setup()
 void
 fs_visitor::split_virtual_grfs()
 {
+   /* Compact the register file so we eliminate dead vgrfs.  This
+    * only defines split points for live registers, so if we have
+    * too large dead registers they will hit assertions later.
+    */
+   compact_virtual_grfs();
+
    int num_vars = this->alloc.count;
 
    /* Count the total number of registers */