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glsl: Apply the transformation "1/rsq(x) == sqrt(x)" in opt_algebraic.

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The comment was stale, because the lowering in question wasn't happening
in lower_instructions.cpp.  Presumably if the lowering ever moves there,
we can plumb the lowering mask through to opt_algebraic.

total instructions in shared programs: 1618696 -> 1616810 (-0.12%)
instructions in affected programs:     243018 -> 241132 (-0.78%)
GAINED:                                0
LOST:                                  0

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
This commit is contained in:
Eric Anholt 2013-11-07 12:15:13 -08:00
parent 477f8cd08b
commit aa6d7bc6d6
1 changed files with 4 additions and 3 deletions
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7
src/glsl/opt_algebraic.cpp
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@ -420,10 +420,11 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
if (op_expr[0] && op_expr[0]->operation == ir_unop_rcp)
return op_expr[0]->operands[0];
/* FINISHME: We should do rcp(rsq(x)) -> sqrt(x) for some
* backends, except that some backends will have done sqrt ->
* rcp(rsq(x)) and we don't want to undo it for them.
/* While ir_to_mesa.cpp will lower sqrt(x) to rcp(rsq(x)), it does so at
* its IR level, so we can always apply this transformation.
*/
if (op_expr[0] && op_expr[0]->operation == ir_unop_rsq)
return sqrt(op_expr[0]->operands[0]);
/* As far as we know, all backends are OK with rsq. */
if (op_expr[0] && op_expr[0]->operation == ir_unop_sqrt) {