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glsl: Optimize (x + y cmp 0) into (x cmp -y). 

Cuts a small handful of instructions in Serious Sam 3:

instructions in affected programs:     4692 -> 4666 (-0.55%)

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
This commit is contained in:
Matt Turner 2014-03-29 12:31:24 -07:00
parent 6499ecafa5
commit 34ec1a24d6
1 changed files with 22 additions and 0 deletions
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22
src/glsl/opt_algebraic.cpp
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@ -445,6 +445,28 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
}
break;
case ir_binop_less:
case ir_binop_lequal:
case ir_binop_greater:
case ir_binop_gequal:
case ir_binop_equal:
case ir_binop_nequal:
for (int add_pos = 0; add_pos < 2; add_pos++) {
ir_expression *add = op_expr[add_pos];
if (!add || add->operation != ir_binop_add)
continue;
ir_constant *zero = op_const[1 - add_pos];
if (!is_vec_zero(zero))
continue;
return new(mem_ctx) ir_expression(ir->operation,
add->operands[0],
neg(add->operands[1]));
}
break;
case ir_binop_rshift:
case ir_binop_lshift:
/* 0 >> x == 0 */