}
}
-/**
- * Try to replace IF/MOV/ELSE/MOV/ENDIF with SEL.
- *
- * Many GLSL shaders contain the following pattern:
- *
- * x = condition ? foo : bar
- *
- * The compiler emits an ir_if tree for this, since each subexpression might be
- * a complex tree that could have side-effects or short-circuit logic.
- *
- * However, the common case is to simply select one of two constants or
- * variable values---which is exactly what SEL is for. In this case, the
- * assembly looks like:
- *
- * (+f0) IF
- * MOV dst src0
- * ELSE
- * MOV dst src1
- * ENDIF
- *
- * which can be easily translated into:
- *
- * (+f0) SEL dst src0 src1
- *
- * If src0 is an immediate value, we promote it to a temporary GRF.
- */
-bool
-fs_visitor::try_replace_with_sel()
-{
- fs_inst *endif_inst = (fs_inst *) instructions.get_tail();
- assert(endif_inst->opcode == BRW_OPCODE_ENDIF);
-
- /* Pattern match in reverse: IF, MOV, ELSE, MOV, ENDIF. */
- int opcodes[] = {
- BRW_OPCODE_IF, BRW_OPCODE_MOV, BRW_OPCODE_ELSE, BRW_OPCODE_MOV,
- };
-
- fs_inst *match = (fs_inst *) endif_inst->prev;
- for (int i = 0; i < 4; i++) {
- if (match->is_head_sentinel() || match->opcode != opcodes[4-i-1])
- return false;
- match = (fs_inst *) match->prev;
- }
-
- /* The opcodes match; it looks like the right sequence of instructions. */
- fs_inst *else_mov = (fs_inst *) endif_inst->prev;
- fs_inst *then_mov = (fs_inst *) else_mov->prev->prev;
- fs_inst *if_inst = (fs_inst *) then_mov->prev;
-
- /* Check that the MOVs are the right form. */
- if (then_mov->dst.equals(else_mov->dst) &&
- !then_mov->is_partial_write() &&
- !else_mov->is_partial_write()) {
-
- /* Remove the matched instructions; we'll emit a SEL to replace them. */
- while (!if_inst->next->is_tail_sentinel())
- if_inst->next->exec_node::remove();
- if_inst->exec_node::remove();
-
- /* Only the last source register can be a constant, so if the MOV in
- * the "then" clause uses a constant, we need to put it in a temporary.
- */
- fs_reg src0(then_mov->src[0]);
- if (src0.file == IMM) {
- src0 = vgrf(glsl_type::float_type);
- src0.type = then_mov->src[0].type;
- bld.MOV(src0, then_mov->src[0]);
- }
-
- if (if_inst->conditional_mod) {
- /* Sandybridge-specific IF with embedded comparison */
- bld.CMP(bld.null_reg_d(), if_inst->src[0], if_inst->src[1],
- if_inst->conditional_mod);
- set_predicate(BRW_PREDICATE_NORMAL,
- bld.emit(BRW_OPCODE_SEL, then_mov->dst,
- src0, else_mov->src[0]));
- } else {
- /* Separate CMP and IF instructions */
- set_predicate_inv(if_inst->predicate, if_inst->predicate_inverse,
- bld.emit(BRW_OPCODE_SEL, then_mov->dst,
- src0, else_mov->src[0]));
- }
-
- return true;
- }
-
- return false;
-}
-
/** Emits a dummy fragment shader consisting of magenta for bringup purposes. */
void
fs_visitor::emit_dummy_fs()