optimization/7799: [3.2/3.3 regression] Loop bug with optimization flag -Os in gcc

[Eric Botcazou]

> This transformation is IMHO illegal because there is no way to make the
> comparison in general equivialent to that in the original for loop.
> If p is initially 0x7ffffffc the comparison must be treated as unsigned,
> however, if p is initially 0xfffffffc the comparison must be treated as
> signed.

Well-known deficiency of the strength reduction pass (see the testcase 
testsuite/gcc.c-torture/execute/loop-2e.c which is XFAILed on x86 at -Os).

-- 
Eric Botcazou