| Message ID | 20180117201040.GY2063@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | [C++] Avoid appending a useless __builtin_unreachable in functions which do return (PR c++/83897) | expand |
OK. On Wed, Jan 17, 2018 at 3:10 PM, Jakub Jelinek <jakub@redhat.com> wrote: > Hi! > > I've noticed several testcases recently that have a dead > __builtin_unreachable call in functions right after return stmt. > They are optimized away after a while (typically in the cfg pass), but we > don't really need to generate them when there is the return. > The reason we don't find it is because it is wrapped in some cases in > CLEANUP_POINT_EXPR. That doesn't change anything on the function actually > ending with a return. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? > > 2018-01-17 Jakub Jelinek <jakub@redhat.com> > > PR c++/83897 > * cp-gimplify.c (cp_maybe_instrument_return): Handle > CLEANUP_POINT_EXPR. > > * g++.dg/cpp0x/pr83897.C: New test. > > --- gcc/cp/cp-gimplify.c.jj 2018-01-11 18:58:48.348391787 +0100 > +++ gcc/cp/cp-gimplify.c 2018-01-16 17:24:41.087336680 +0100 > @@ -1581,6 +1581,7 @@ cp_maybe_instrument_return (tree fndecl) > t = BIND_EXPR_BODY (t); > continue; > case TRY_FINALLY_EXPR: > + case CLEANUP_POINT_EXPR: > t = TREE_OPERAND (t, 0); > continue; > case STATEMENT_LIST: > --- gcc/testsuite/g++.dg/cpp0x/pr83897.C.jj 2018-01-16 17:41:54.723256147 +0100 > +++ gcc/testsuite/g++.dg/cpp0x/pr83897.C 2018-01-16 17:41:34.274257947 +0100 > @@ -0,0 +1,13 @@ > +// PR c++/83897 > +// { dg-do compile { target c++11 } } > +// { dg-options "-O2 -fdump-tree-gimple" } > +// { dg-final { scan-tree-dump-not "__builtin_unreachable" "gimple" } } > + > +struct A {}; > +struct B { int a; int b = 5; }; > + > +A > +bar (B) > +{ > + return {}; > +} > > Jakub
--- gcc/cp/cp-gimplify.c.jj 2018-01-11 18:58:48.348391787 +0100 +++ gcc/cp/cp-gimplify.c 2018-01-16 17:24:41.087336680 +0100 @@ -1581,6 +1581,7 @@ cp_maybe_instrument_return (tree fndecl) t = BIND_EXPR_BODY (t); continue; case TRY_FINALLY_EXPR: + case CLEANUP_POINT_EXPR: t = TREE_OPERAND (t, 0); continue; case STATEMENT_LIST: --- gcc/testsuite/g++.dg/cpp0x/pr83897.C.jj 2018-01-16 17:41:54.723256147 +0100 +++ gcc/testsuite/g++.dg/cpp0x/pr83897.C 2018-01-16 17:41:34.274257947 +0100 @@ -0,0 +1,13 @@ +// PR c++/83897 +// { dg-do compile { target c++11 } } +// { dg-options "-O2 -fdump-tree-gimple" } +// { dg-final { scan-tree-dump-not "__builtin_unreachable" "gimple" } } + +struct A {}; +struct B { int a; int b = 5; }; + +A +bar (B) +{ + return {}; +}