Erik Faye-Lund <kusmab...@gmail.com> writes: > Why is this tagged as i965/fs, when everything seems to happen in the > glsl-optimizer? > > On Thu, Oct 24, 2013 at 5:53 PM, Eric Anholt <e...@anholt.net> wrote: >> 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). >> --- >> src/glsl/opt_algebraic.cpp | 8 ++++++++ >> 1 file changed, 8 insertions(+) >> >> diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp >> index 37b2f02..ff06cfc 100644 >> --- a/src/glsl/opt_algebraic.cpp >> +++ b/src/glsl/opt_algebraic.cpp >> @@ -387,6 +387,14 @@ ir_algebraic_visitor::handle_expression(ir_expression >> *ir) >> } >> break; >> >> + case ir_binop_rshift: >> + case ir_binop_lshift: >> + if (is_vec_zero(op_const[0])) >> + return ir->operands[1]; >> + else if (is_vec_zero(op_const[1])) >> + return ir->operands[0]; >> + break; >> + > > Maybe update progress inside the conditionals also? > > But wait a minute. x shifted by 0 is x, so the latter part looks > correct. But the first conditional seems to assume that 0 sifted by x > is x, but it's really 0, no? Shouldn't both cases return > ir->operands[0]? What am I missing?
You're not missing anything -- it was just copy-and-paste fail. New patch series incoming that should fix that, plus should reduce other copy and paste fail in this code.
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