glsl/opt_algebraic: disable invalid optimization

When operators other than eq and ne are involved we can't really
move operands around and negate them because such transformation
may change the value of the whole expression.

Some examples:

For unsigned var:
0 >= 1u + var would eventually become 0xffffffff >= var,
which would always evaluate to true, when original expression
was true only for var == 0xffffffff.

For signed var:
0 >= 1 + var would become -1 >= var, which would evaluate to
false for var == 2147483647, when original expression evaluated
to true (because signed overflow is defined to wrap around in
glsl, 1 + 2147483647 == -2147483648, so 0 >= -2147483648).

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5226
Fixes: 34ec1a24d61 ("glsl: Optimize (x + y cmp 0) into (x cmp -y).")
Signed-off-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12359>

diff --git a/src/compiler/glsl/opt_algebraic.cpp b/src/compiler/glsl/opt_algebraic.cpp
index 7cef4fc..14d6e13 100644 (file)
--- a/src/compiler/glsl/opt_algebraic.cpp
+++ b/src/compiler/glsl/opt_algebraic.cpp
@@ -708,8 +708,6 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
       }
       break;
 
-   case ir_binop_less:
-   case ir_binop_gequal:
    case ir_binop_equal:
    case ir_binop_nequal:
       for (int add_pos = 0; add_pos < 2; add_pos++) {