[Bug tree-optimization/56982] [4.8 Regression] Bad optimization with setjmp()

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56982

--- Comment #13 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
Created attachment 30431
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30431&action=edit
another example of wrong compilation

This is another example where the optimization can
go wrong.

The attached program produces expected results if
compiled with -O0:
x=0, a=1
x=1, a=1
a=1

But if compiled with -O3 and if the value "a" is placed
in a register the result is like this:
x=0, a=1
x=1, a=0
a=0

That is because longjmp has more semantic than just a branch:
It branches to the setjmp, and restores all callee saved registers to
the previos value.