| Message ID | 20170322131328.GD11094@tucnak |
|---|---|
| State | New |
| Headers | show |
On Wed, 22 Mar 2017, Jakub Jelinek wrote: > On Wed, Mar 22, 2017 at 09:59:09AM +0100, Richard Biener wrote: > > Yeah, changing it to VAR_P and expanding the comment so it says > > it avoids incorrect promotion to readonly-static. (so it _is_ > > fishy that we have multiple assignments to TREE_READONLY objects > > given that code looks at a single assignment only) > > So like this? Yes. Thanks, Richard. > 2017-03-22 Jakub Jelinek <jakub@redhat.com> > > PR c++/80129 > * gimplify.c (gimplify_modify_expr_rhs) <case COND_EXPR>: Clear > TREE_READONLY on result if writing it more than once. > > * g++.dg/torture/pr80129.C: New test. > > --- gcc/gimplify.c.jj 2017-03-21 07:56:55.000000000 +0100 > +++ gcc/gimplify.c 2017-03-21 13:37:45.555612652 +0100 > @@ -5098,6 +5098,14 @@ gimplify_modify_expr_rhs (tree *expr_p, > if (ret != GS_ERROR) > ret = GS_OK; > > + /* If we are going to write RESULT more than once, clear > + TREE_READONLY flag, otherwise we might incorrectly promote > + the variable to static const and initialize it at compile > + time in one of the branches. */ > + if (VAR_P (result) > + && TREE_TYPE (TREE_OPERAND (cond, 1)) != void_type_node > + && TREE_TYPE (TREE_OPERAND (cond, 2)) != void_type_node) > + TREE_READONLY (result) = 0; > if (TREE_TYPE (TREE_OPERAND (cond, 1)) != void_type_node) > TREE_OPERAND (cond, 1) > = build2 (code, void_type_node, result, > --- gcc/testsuite/g++.dg/torture/pr80129.C.jj 2017-03-21 13:40:04.179852313 +0100 > +++ gcc/testsuite/g++.dg/torture/pr80129.C 2017-03-21 13:41:32.121735570 +0100 > @@ -0,0 +1,14 @@ > +// PR c++/80129 > +// { dg-do run } > +// { dg-options "-std=c++11" } > + > +struct A { bool a; int b; }; > + > +int > +main () > +{ > + bool c = false; > + const A x = c ? A {true, 1} : A {false, 0}; > + if (x.a) > + __builtin_abort (); > +} > > Jakub > >
--- gcc/gimplify.c.jj 2017-03-21 07:56:55.000000000 +0100 +++ gcc/gimplify.c 2017-03-21 13:37:45.555612652 +0100 @@ -5098,6 +5098,14 @@ gimplify_modify_expr_rhs (tree *expr_p, if (ret != GS_ERROR) ret = GS_OK; + /* If we are going to write RESULT more than once, clear + TREE_READONLY flag, otherwise we might incorrectly promote + the variable to static const and initialize it at compile + time in one of the branches. */ + if (VAR_P (result) + && TREE_TYPE (TREE_OPERAND (cond, 1)) != void_type_node + && TREE_TYPE (TREE_OPERAND (cond, 2)) != void_type_node) + TREE_READONLY (result) = 0; if (TREE_TYPE (TREE_OPERAND (cond, 1)) != void_type_node) TREE_OPERAND (cond, 1) = build2 (code, void_type_node, result, --- gcc/testsuite/g++.dg/torture/pr80129.C.jj 2017-03-21 13:40:04.179852313 +0100 +++ gcc/testsuite/g++.dg/torture/pr80129.C 2017-03-21 13:41:32.121735570 +0100 @@ -0,0 +1,14 @@ +// PR c++/80129 +// { dg-do run } +// { dg-options "-std=c++11" } + +struct A { bool a; int b; }; + +int +main () +{ + bool c = false; + const A x = c ? A {true, 1} : A {false, 0}; + if (x.a) + __builtin_abort (); +}