[Bug target/67089] [4.9/5/6 Regression] Integer overflow checks not optimized on x86/x86_64

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67089

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 36830
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36830&action=edit
gcc6-pr67089.patch

Untested patch for matching hand written unsigned addition/subtraction overflow
checks as {ADD,SUB}_OVERFLOW if target has u{add,sub}v4 optabs.