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glsl: Optimize round-half-up pattern. 

Hurts some Psychonauts shaders, but after the next patch (which this
enables) they're fewer instructions than before this patch.
This commit is contained in:
Matt Turner 2015-01-28 10:09:14 -08:00
parent a5455ab1ca
commit c262b2b582
1 changed files with 33 additions and 0 deletions
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33
src/glsl/opt_algebraic.cpp
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@ -514,6 +514,39 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
if (op_const[1] && !op_const[0])
reassociate_constant(ir, 1, op_const[1], op_expr[0]);
/* Optimizes
*
* (mul (floor (add (abs x) 0.5) (sign x)))
*
* into
*
* (trunc (add x (mul (sign x) 0.5)))
*/
for (int i = 0; i < 2; i++) {
ir_expression *sign_expr = ir->operands[i]->as_expression();
ir_expression *floor_expr = ir->operands[1 - i]->as_expression();
if (!sign_expr || sign_expr->operation != ir_unop_sign ||
!floor_expr || floor_expr->operation != ir_unop_floor)
continue;
ir_expression *add_expr = floor_expr->operands[0]->as_expression();
for (int j = 0; j < 2; j++) {
ir_expression *abs_expr = add_expr->operands[j]->as_expression();
if (!abs_expr || abs_expr->operation != ir_unop_abs)
continue;
ir_constant *point_five = add_expr->operands[1 - j]->as_constant();
if (!point_five->is_value(0.5, 0))
continue;
if (abs_expr->operands[0]->equals(sign_expr->operands[0])) {
return trunc(add(abs_expr->operands[0],
mul(sign_expr, point_five)));
}
}
}
break;
case ir_binop_div: