http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51644
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-12-21
09:51:45 UTC ---
Caused by r181172 aka TREE_CLOBBER_P. The problem is that we have before
*.cfg:
__builtin_va_start (&args, 0);
b (s, &args);
__builtin_va_end (&args);
finally_tmp.0 = 1;
<D.2917>:
args = {CLOBBER};
switch (finally_tmp.0) <default: <D.2921>, default: <D.2921>, case 1:
<D.2918>>
<D.2918>:
goto <D.2919>;
<D.2919>:
return;
<D.2920>:
finally_tmp.0 = 0;
goto <D.2917>;
<D.2921>:
resx 1
and *.cfg pass obviously optimizes away anything after the noreturn call:
<bb 2>:
__builtin_va_start (&args, 0);
b (s, &args);
<L5>:
return;
<L3>:
finally_tmp.0 = 0;
args = {CLOBBER};
switch (finally_tmp.0) <default: <L4>, case 1: <L5>>
<L4>:
resx 1
but the warn_function_return pass is immediately after that (and, this is -O0
anyway), so nothing optimizes the switch away into simple fall through into the
resx 1 block. At -O and above we don't warn, because the *.eh pass before
*.cfg pass optimizes this.
So, IMHO to fix this, we need to do 2 things:
1) in decide_copy_try_finally reconsider
if (!optimize)
return ndests == 1;
if finally contains only gimple_clobber_p stmts
2) estimate_num_insns should return 0 for gimple_clobber_p stmts
