On 03/20/2013 05:36 PM, Eric Anholt wrote:
This happens quite a bit with varying-index uniform loads. We could also
do better by avoiding the MACH entirely, but there's no reason not to at
least take this step.
---
src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
Okay, yeah, so we constant propagate the immediate into both the MUL and
the MACH. That makes sense...may free up a register.
It'd be nice to eliminate it if the constant is small enough, yeah.
Reviewed-by: Kenneth Graunke <kenn...@whitecape.org>
diff --git a/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
index 194ed07..2d0391a 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
@@ -261,6 +261,7 @@ fs_visitor::try_constant_propagate(fs_inst *inst, acp_entry
*entry)
progress = true;
break;
+ case BRW_OPCODE_MACH:
case BRW_OPCODE_MUL:
case BRW_OPCODE_ADD:
if (i == 1) {
@@ -268,10 +269,11 @@ fs_visitor::try_constant_propagate(fs_inst *inst,
acp_entry *entry)
progress = true;
} else if (i == 0 && inst->src[1].file != IMM) {
/* Fit this constant in by commuting the operands.
- * Exception: we can't do this for 32-bit integer MUL
+ * Exception: we can't do this for 32-bit integer MUL/MACH
* because it's asymmetric.
*/
- if (inst->opcode == BRW_OPCODE_MUL &&
+ if ((inst->opcode == BRW_OPCODE_MUL ||
+ inst->opcode == BRW_OPCODE_MACH) &&
(inst->src[1].type == BRW_REGISTER_TYPE_D ||
inst->src[1].type == BRW_REGISTER_TYPE_UD))
break;
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