path: root/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
diff options
authorMatt Turner <>2013-09-26 13:38:11 -0700
committerMatt Turner <>2013-10-07 10:43:19 -0700
commit6ff8f0630833396fb7aff266657d4e1a04400719 (patch)
treedae17d5c3df68cdbfdac8799fc528aba585a8fba /src/mesa/drivers/dri/i965/brw_fs_cse.cpp
parent06e41a02a3564b00404dd3dd5d6f6b5897df36e9 (diff)
i965/fs: Disable CSE on instructions writing to HW_REG.
CSE would otherwise combine the two mul(8) emitted by [iu]mulExtended: mul(8) acc0 x y mach(8) null x y mov(8) lsb acc0 ... mul(8) acc0 x y mach(8) msb x y Into: mul(8) temp x y mov(8) acc0 temp mach(8) null x y mov(8) lsb acc0 ... mov(8) acc0 temp mach(8) msb x y But mul(8) into the accumulator produces more than 32-bits of precision, which is required and lost if multiplying into a general register and moving to the accumulator. Reviewed-by: Eric Anholt <>
Diffstat (limited to 'src/mesa/drivers/dri/i965/brw_fs_cse.cpp')
1 files changed, 2 insertions, 1 deletions
diff --git a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
index ccd4e5edd1..61b3aeb5ac 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
@@ -98,7 +98,8 @@ fs_visitor::opt_cse_local(bblock_t *block, exec_list *aeb)
if (is_expression(inst) &&
!inst->predicate &&
!inst->is_partial_write() &&
- !inst->conditional_mod)
+ !inst->conditional_mod &&
+ inst->dst.file != HW_REG)
bool found = false;