From ea0f0eb6c0a8b20bcce50c63170df94892a51142 Mon Sep 17 00:00:00 2001 From: Matt Turner Date: Tue, 10 Feb 2015 12:31:37 -0800 Subject: [PATCH] glsl: Optimize 1/exp(x) into exp(-x). Lots of shaders divide by exp2(...) which we turn into a multiplication by the reciprocal. We can avoid the reciprocal by simply negating exp2's argument. total instructions in shared programs: 5947154 -> 5946695 (-0.01%) instructions in affected programs: 118661 -> 118202 (-0.39%) helped: 380 Reviewed-by: Jason Ekstrand Reviewed-by: Ian Romanick --- src/glsl/opt_algebraic.cpp | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp index c6f4a9c786d..616ed37b952 100644 --- a/src/glsl/opt_algebraic.cpp +++ b/src/glsl/opt_algebraic.cpp @@ -747,6 +747,12 @@ 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]; + if (op_expr[0] && (op_expr[0]->operation == ir_unop_exp2 || + op_expr[0]->operation == ir_unop_exp)) { + return new(mem_ctx) ir_expression(op_expr[0]->operation, ir->type, + neg(op_expr[0]->operands[0])); + } + /* 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. */ -- 2.30.2