glsl2: Add a pass to transform ir_binop_sub to add(op0, neg(op1))

All the current HW backends transform subtract to adding the negation,
so I haven't bothered peepholing it back out in Mesa IR.  This allows
some subtract of subtract to get removed in ir_algebraic.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/mesa/program/ir_to_mesa.cpp b/src/mesa/program/ir_to_mesa.cpp
index 5a272ab88a1..a9a6f977c01 100644
--- a/src/mesa/program/ir_to_mesa.cpp
+++ b/src/mesa/program/ir_to_mesa.cpp
@@ -2570,6 +2570,7 @@ _mesa_glsl_compile_shader(GLcontext *ctx, struct gl_shader *shader)
       do_mat_op_to_vec(shader->ir);
       do_mod_to_fract(shader->ir);
       do_div_to_mul_rcp(shader->ir);
+      do_sub_to_add_neg(shader->ir);
 
       /* Optimization passes */
       bool progress;