From: Ian Romanick <ian.d.roman...@intel.com>
Shader-db results:
Ivy Bridge (0x0166):
total instructions in shared programs: 6291662 -> 6291642 (-0.00%)
instructions in affected programs: 3383 -> 3363 (-0.59%)
helped: 20
Haswell (0x0426):
total instructions in shared programs: 5779036 -> 5779016 (-0.00%)
instructions in affected programs: 3050 -> 3030 (-0.66%)
helped: 20
Broadwell (0x162E):
total instructions in shared programs: 6822830 -> 6822810 (-0.00%)
instructions in affected programs: 3038 -> 3018 (-0.66%)
helped: 20
No change on GM45, Iron Lake, Sandy Bridge, or any platform with NIR.
Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
---
src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 30 ++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index bde9492..f1e9fb5 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -2631,6 +2631,36 @@ fs_visitor::emit_bool_to_cond_code(ir_rvalue *ir)
return;
}
+ /* Try to generate the condition code more efficiently for gl_FrontFacing
+ * and !gl_FrontFacing.
+ */
+ enum brw_conditional_mod cm;
+ ir_dereference_variable *deref;
+
+ if (expr && expr->operation == ir_unop_logic_not) {
+ cm = BRW_CONDITIONAL_NZ;
+ deref = expr->operands[0]->as_dereference_variable();
+ } else {
+ cm = BRW_CONDITIONAL_Z;
+ deref = ir->as_dereference_variable();
+ }
+
+ if (deref != NULL && strcmp(deref->var->name, "gl_FrontFacing") == 0) {
+ if (brw->gen >= 6) {
+ /* Bit 15 of g0.0 is 0 if the polygon is front facing. */
+ emit(AND(reg_null_d, retype(brw_vec1_grf(0, 0), BRW_REGISTER_TYPE_D),
+ fs_reg(0x00008000)))
+ ->conditional_mod = cm;
+ } else {
+ /* Bit 31 of g1.6 is 0 if the polygon is front facing. */
+ emit(AND(reg_null_d, retype(brw_vec1_grf(1, 6), BRW_REGISTER_TYPE_D),
+ fs_reg(0x80000000)))
+ ->conditional_mod = cm;
+ }
+
+ return;
+ }
+
fs_reg op[3];
assert(expr->get_num_operands() <= 3);
--
2.1.0
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