From 08bf52712e9dbd32ea3e4855c3446eba624fc890 Mon Sep 17 00:00:00 2001 From: Eric Anholt Date: Mon, 21 Oct 2013 17:01:49 -0700 Subject: glsl: Drop no-op shifts involving 0. I noticed this in a shader in Unigine Heaven that was spilling. While it doesn't really reduce register pressure, it shaves a few instructions anyway (7955 -> 7882). v2: Fix turning "0 >> x" into "x" instead of "0" (caught by Erik Faye-Lund). Reviewed-by: Kenneth Graunke Reviewed-by: Matt Turner --- src/glsl/opt_algebraic.cpp | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'src/glsl/opt_algebraic.cpp') diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp index 2e33dfeb217..a07e153ae92 100644 --- a/src/glsl/opt_algebraic.cpp +++ b/src/glsl/opt_algebraic.cpp @@ -346,6 +346,16 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir) } break; + case ir_binop_rshift: + case ir_binop_lshift: + /* 0 >> x == 0 */ + if (is_vec_zero(op_const[0])) + return ir->operands[0]; + /* x >> 0 == x */ + if (is_vec_zero(op_const[1])) + return ir->operands[0]; + break; + case ir_binop_logic_and: /* FINISHME: Also simplify (a && a) to (a). */ if (is_vec_one(op_const[0])) { -- cgit v1.2.3