https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61502
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Blocks| |85800
--- Comment #30 from Richard Biener <rguenth at gcc dot gnu.org> ---
Another interesting example in PR85800 where the offending "bad" transformation
is
for char a, b
if (a == b)
a[i] = a;
else
a[i] = b;
if-convert that to
a[i] = b;
because a and b have different pointer provenance -- runtime equal pointers
&x and &y+1 (one-after-end) again. The if-converted result results in
a[i] having same provenance as b rather than "both" (GCC happily tracks
provenance union).
In isolation avoiding this kind of transforms is bad (consider this is isolated
into a separate function and later inlined).
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85800
[Bug 85800] A miscompilation bug with unsigned char
