[Bug tree-optimization/50865] Invalid code generation for INT64_MIN % 1 on x86_64

[joseph at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50865

--- Comment #10 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2011-10-25 17:13:51 UTC ---
On Tue, 25 Oct 2011, jaak at ristioja dot ee wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50865
> 
> --- Comment #9 from Jaak Ristioja <jaak at ristioja dot ee> 2011-10-25 16:37:48 UTC ---
> (In reply to comment #8)
> > Well, they are equivalent where they are both defined, or if you apply C99 
> > rules to infinite-precision integers.  The problem here is that INT_MIN % 
> > -1 is undefined (explicitly in C1X) and so a transformation of INT_MIN % 1 
> > into INT_MIN % -1 is unsafe (the other way round, transforming undefined 
> > behavior to defined, is fine at least in the absence of -ftrapv).
> 
> But INT_MIN % 1 is still defined to be zero?

Yes.  INT_MIN % 1 is defined to be zero, since the infinite-precision 
values of both INT_MIN / 1 and INT_MIN % 1 are representable.  INT_MIN % 
-1 is undefined because the infinite-precision value of INT_MIN / -1 is 
not representable in int.