From: Ian Romanick <ian.d.roman...@intel.com>
An expression like -(x * 8) becomes (x * -8).
Much of the hurt caused by this change appears to be from CSE not being
able to see (x * -8) and (x * 8) as common. Previously -(x * 8) and (x
* 8) would have had a common subexpression. Later patches address this
at the GLSL IR level, but additional work will be needed in NIR and the
i965 backend.
Shader-db results:
GM45 (0x2A42):
total instructions in shared programs: 3544299 -> 3544158 (-0.00%)
instructions in affected programs: 19768 -> 19627 (-0.71%)
helped: 33
HURT: 52
Iron Lake (0x0046):
total instructions in shared programs: 4974090 -> 4973887 (-0.00%)
instructions in affected programs: 22831 -> 22628 (-0.89%)
helped: 54
HURT: 55
Sandy Bridge (0x0116):
total instructions in shared programs: 6799711 -> 6799717 (0.00%)
instructions in affected programs: 1410 -> 1416 (0.43%)
helped: 9
HURT: 5
Sandy Bridge (0x0116) NIR:
total instructions in shared programs: 6789759 -> 6785948 (-0.06%)
instructions in affected programs: 929330 -> 925519 (-0.41%)
helped: 1689
HURT: 2129
GAINED: 3
LOST: 6
Ivy Bridge (0x0166):
total instructions in shared programs: 6274069 -> 6274097 (0.00%)
instructions in affected programs: 1275 -> 1303 (2.20%)
helped: 3
HURT: 12
Ivy Bridge (0x0166) NIR:
total instructions in shared programs: 6300857 -> 6296339 (-0.07%)
instructions in affected programs: 783687 -> 779169 (-0.58%)
helped: 1704
HURT: 1858
GAINED: 7
LOST: 3
Haswell (0x0426):
total instructions in shared programs: 5760186 -> 5760202 (0.00%)
instructions in affected programs: 1176 -> 1192 (1.36%)
helped: 4
HURT: 11
Haswell (0x0426) NIR:
total instructions in shared programs: 5780293 -> 5766919 (-0.23%)
instructions in affected programs: 749765 -> 736391 (-1.78%)
helped: 3281
HURT: 217
GAINED: 1
LOST: 3
Broadwell (0x162E):
total instructions in shared programs: 6808264 -> 6808264 (0.00%)
instructions in affected programs: 1224 -> 1224 (0.00%)
helped: 5
HURT: 10
Broadwell (0x162E) NIR:
total instructions in shared programs: 6995761 -> 6982615 (-0.19%)
instructions in affected programs: 782786 -> 769640 (-1.68%)
helped: 3452
HURT: 230
GAINED: 10
LOST: 3
Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
Cc: Jason Ekstrand <jason.ekstr...@intel.com>
---
src/glsl/opt_algebraic.cpp | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
index 0f15f52..af22bed 100644
--- a/src/glsl/opt_algebraic.cpp
+++ b/src/glsl/opt_algebraic.cpp
@@ -443,6 +443,27 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
if (op_expr[0]->operation == ir_unop_neg) {
return op_expr[0]->operands[0];
}
+
+ /* Replace -(x * constant) with (x * -constant).
+ */
+ if (op_expr[0]->operation == ir_binop_mul) {
+ for (i = 0; i < 2; i++) {
+ if (op_expr[0]->operands[i]->as_constant()) {
+ ir_expression *const tmp_expr =
+ new(mem_ctx) ir_expression(ir_unop_neg,
+ op_expr[0]->operands[i]);
+
+ /* Constant-fold the expression now to (possibly) save an
+ * interation through the optimization loop.
+ */
+ op_expr[0]->operands[i] =
+ tmp_expr->constant_expression_value();
+
+ assert(op_expr[0]->operands[i] != NULL);
+ return op_expr[0];
+ }
+ }
+ }
break;
case ir_unop_exp:
--
2.1.0
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/mesa-dev
