From 6ff8f0630833396fb7aff266657d4e1a04400719 Mon Sep 17 00:00:00 2001 From: Matt Turner Date: Thu, 26 Sep 2013 13:38:11 -0700 Subject: [PATCH] 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 --- src/mesa/drivers/dri/i965/brw_fs_cse.cpp | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp index ccd4e5edd1e..61b3aeb5ac1 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; -- 2.30.2