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ir_to_mesa: Try to avoid emitting a MOV_SAT to saturate an expression tree.

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Fixes a regression in codegen quality for ff_fragment_shader
conversion to GLSL -- glean texCombine produces 7.5% fewer Mesa IR
instructions.
This commit is contained in:
Eric Anholt 2011-07-22 13:54:15 -07:00
parent 6bd5f43f21
commit 62722d90af
1 changed files with 24 additions and 4 deletions
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20
src/mesa/program/ir_to_mesa.cpp
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@ -915,10 +915,30 @@ ir_to_mesa_visitor::try_emit_sat(ir_expression *ir)
sat_src->accept(this);
src_reg src = this->result;
/* If we generated an expression instruction into a temporary in
* processing the saturate's operand, apply the saturate to that
* instruction. Otherwise, generate a MOV to do the saturate.
*
* Note that we have to be careful to only do this optimization if
* the instruction in question was what generated src->result. For
* example, ir_dereference_array might generate a MUL instruction
* to create the reladdr, and return us a src reg using that
* reladdr. That MUL result is not the value we're trying to
* saturate.
*/
ir_expression *sat_src_expr = sat_src->as_expression();
ir_to_mesa_instruction *new_inst;
new_inst = (ir_to_mesa_instruction *)this->instructions.get_tail();
if (sat_src_expr && (sat_src_expr->operation == ir_binop_mul ||
sat_src_expr->operation == ir_binop_add ||
sat_src_expr->operation == ir_binop_dot)) {
new_inst->saturate = true;
} else {
this->result = get_temp(ir->type);
ir_to_mesa_instruction *inst;
inst = emit(ir, OPCODE_MOV, dst_reg(this->result), src);
inst->saturate = true;
}
return true;
}