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| author | Eric Anholt <eric@anholt.net> | 2013-10-21 17:01:49 -0700 |
|---|---|---|
| committer | Eric Anholt <eric@anholt.net> | 2013-10-28 14:07:31 -0700 |
| commit | 08bf52712e9dbd32ea3e4855c3446eba624fc890 (patch) | |
| tree | 7c30380a6b9becc9c3977629a4c5edbe5044d1e9 /src/glsl/opt_algebraic.cpp | |
| parent | 3a0fdf2ab6ab9c66c50645409d8f79bcd6f8ed1b (diff) | |
| download | external_mesa3d-08bf52712e9dbd32ea3e4855c3446eba624fc890.zip external_mesa3d-08bf52712e9dbd32ea3e4855c3446eba624fc890.tar.gz external_mesa3d-08bf52712e9dbd32ea3e4855c3446eba624fc890.tar.bz2 | |
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 <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Diffstat (limited to 'src/glsl/opt_algebraic.cpp')
| -rw-r--r-- | src/glsl/opt_algebraic.cpp | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp index 2e33dfe..a07e153 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])) { |