commit c7a952858e846738ee9983796a20585b6635429c

Author: Aaron Merey <amerey@redhat.com>

Date:   Wed Jun 20 18:26:36 2018 -0400

    bpf translator: binary operations now act on copy of left operand.

    Needed for cases where evaluating right operand causes side effects that

    mutate the left (ex. x + x++).

diff --git a/bpf-translate.cxx b/bpf-translate.cxx

index fd9021e70..adfef97a5 100644

--- a/bpf-translate.cxx

+++ b/bpf-translate.cxx

@@ -1008,7 +1008,11 @@ bpf_unparser::visit_binary_expression (binary_expression* e)

   else

     throw SEMANTIC_ERROR (_("unhandled binary operator"), e->tok);

-  value *s0 = emit_expr (e->left);

+  value *s0 = this_prog.new_reg();

+  // copy e->left into a seperate reg incase evaluating e->right

+  // causes e->left to mutate (ex. x + x++).

+  this_prog.mk_mov(this_ins, s0, emit_expr (e->left));

+

   value *s1 = emit_expr (e->right);

   value *d = this_prog.new_reg ();

   this_prog.mk_binary (this_ins, code, d, s0, s1);