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/glsl/linker.cpp b/src/glsl/linker.cpp
index 52c9322788..c462d31ef3 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1284,6 +1284,7 @@ link_shaders(struct gl_shader_program *prog)
       do_mod_to_fract(ir);
       do_div_to_mul_rcp(ir);
       do_explog_to_explog2(ir);
+      do_sub_to_add_neg(ir);
 
       do {
 	 progress = false;