------- Comment #6 from rguenth at gcc dot gnu dot org 2010-08-07 16:19 ------- (In reply to comment #5) > Hi Richard, > > Your explanation doesn't explain why foo1 would emit poorer assembly than > foo3. > > Or for that matter why fooA would emit poorer assembly than fooB. > > In the case of foo1, foo3, fooA, and fooB, dereferencing occurs first, before > casting. Yet only foo3 and fooB generate optimal assembly (so gcc is clearly > "capable" of outputting the desired asm). This is all at -O3, where > "-fdelete-null-pointer-checks" is already enabled.
X* x; X& = *x; is not considered a dereference - internally it is just a pointer assignment we can't derive non-NULL-ness from. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45221
