Mesa (master): ir_to_mesa: use RSQ+MUL instead of RSQ+RCP for SQRT
Marek Olšák
mareko at kemper.freedesktop.org
Tue Aug 31 04:40:22 UTC 2010
Module: Mesa
Branch: master
Commit: 4f189b3bf57a6500953dac49105f160af5fa6468
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=4f189b3bf57a6500953dac49105f160af5fa6468
Author: Marek Olšák <maraeo at gmail.com>
Date: Tue Aug 31 05:38:50 2010 +0200
ir_to_mesa: use RSQ+MUL instead of RSQ+RCP for SQRT
sqrt(x) = 1/rsq(x) = x*rsq(x)
This optimization already was in the old GLSL compiler.
Acked on irc by Eric Anholt.
---
src/mesa/program/ir_to_mesa.cpp | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/src/mesa/program/ir_to_mesa.cpp b/src/mesa/program/ir_to_mesa.cpp
index af6d734..516c991 100644
--- a/src/mesa/program/ir_to_mesa.cpp
+++ b/src/mesa/program/ir_to_mesa.cpp
@@ -880,8 +880,9 @@ ir_to_mesa_visitor::visit(ir_expression *ir)
break;
case ir_unop_sqrt:
+ /* sqrt(x) = x * rsq(x). */
ir_to_mesa_emit_scalar_op1(ir, OPCODE_RSQ, result_dst, op[0]);
- ir_to_mesa_emit_scalar_op1(ir, OPCODE_RCP, result_dst, result_src);
+ ir_to_mesa_emit_op2(ir, OPCODE_MUL, result_dst, result_src, op[0]);
/* For incoming channels < 0, set the result to 0. */
ir_to_mesa_emit_op3(ir, OPCODE_CMP, result_dst,
op[0], src_reg_for_float(0.0), result_src);
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