[Mesa-dev] [PATCH 2/3] i965: Make split_virtual_grfs() call compact_virtual_grfs().

Kenneth Graunke kenneth at whitecape.org
Mon Oct 24 06:44:32 UTC 2016

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.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
 src/mesa/drivers/dri/i965/brw_fs.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 1c7a6e6..31d21ec 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -1687,6 +1687,8 @@ fs_visitor::assign_gs_urb_setup()
+   compact_virtual_grfs();
    int num_vars = this->alloc.count;
    /* Count the total number of registers */

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