On January 19, 2018 10:52:08 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>Before emutls lowering, expressions like &MEM_REF[(whatever)&e].a
>for static __thread e is considered gimple invariant (after all, for
>native TLS we do that too) and gimple invariants are shareable trees.
>lower_emutls* then has code to update the VAR_DECL in there with an
>SSA_NAME
>and if needed, split it appart into another stmt (i.e. manually
>regimplify)
>if needed, but doesn't take into account the possible tree sharing,
>which can result in 1) invalid tree sharing, because after changing the
>VAR_DECL for a SSA_NAME it is no longer gimple invariant 2) might not
>break it appart anymore the second and further times 3) might use
>SSA_NAME
>that doesn't dominate it.
>
>Fixed by checking if we'll need to update the ADDR_EXPR operand or
>anything
>in there and unsharing if so before actually changing it.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
>2018-01-19 Jakub Jelinek <ja...@redhat.com>
>
> PR middle-end/83945
> * tree-emutls.c: Include gimplify.h.
> (lower_emutls_2): New function.
> (lower_emutls_1): If ADDR_EXPR is a gimple invariant and walk_tree
> with lower_emutls_2 callback finds some TLS decl in it, unshare_expr
> it before further processing.
>
> * gcc.dg/tls/pr83945.c: New test.
>
>--- gcc/tree-emutls.c.jj 2018-01-03 10:19:54.790533899 +0100
>+++ gcc/tree-emutls.c 2018-01-19 19:11:14.849321308 +0100
>@@ -34,6 +34,7 @@ along with GCC; see the file COPYING3.
> #include "gimple-walk.h"
> #include "langhooks.h"
> #include "tree-iterator.h"
>+#include "gimplify.h"
>
>/* Whenever a target does not support thread-local storage (TLS)
>natively,
> we can emulate it with some run-time support in libgcc. This will in
>@@ -429,6 +430,20 @@ gen_emutls_addr (tree decl, struct lower
> return addr;
> }
>
>+/* Callback for lower_emutls_1, return non-NULL if there is any TLS
>+ VAR_DECL in the subexpressions. */
>+
>+static tree
>+lower_emutls_2 (tree *ptr, int *walk_subtrees, void *)
>+{
>+ tree t = *ptr;
>+ if (TREE_CODE (t) == VAR_DECL)
>+ return DECL_THREAD_LOCAL_P (t) ? t : NULL_TREE;
>+ else if (!EXPR_P (t))
>+ *walk_subtrees = 0;
>+ return NULL_TREE;
>+}
>+
>/* Callback for walk_gimple_op. D = WI->INFO is a struct
>lower_emutls_data.
> Given an operand *PTR within D->STMT, if the operand references a TLS
> variable, then lower the reference to a call to the runtime. Insert
>@@ -455,6 +470,13 @@ lower_emutls_1 (tree *ptr, int *walk_sub
> {
> bool save_changed;
>
>+ /* Gimple invariants are shareable trees, so before changing
>+ anything in them if we will need to change anything, unshare
>+ them. */
>+ if (is_gimple_min_invariant (t)
>+ && walk_tree (&TREE_OPERAND (t, 0), lower_emutls_2, NULL,
>NULL))
>+ *ptr = t = unshare_expr (t);
>+
> /* If we're allowed more than just is_gimple_val, continue. */
> if (!wi->val_only)
> {
>--- gcc/testsuite/gcc.dg/tls/pr83945.c.jj 2018-01-19 19:16:52.376346273
>+0100
>+++ gcc/testsuite/gcc.dg/tls/pr83945.c 2018-01-19 19:16:25.186344529
>+0100
>@@ -0,0 +1,21 @@
>+/* PR middle-end/83945 */
>+/* { dg-do compile { target tls } } */
>+/* { dg-options "-O2" } */
>+
>+struct S { int a[1]; };
>+__thread struct T { int c; } e;
>+int f;
>+void bar (int);
>+
>+void
>+foo (int f, int x)
>+{
>+ struct S *h = (struct S *) &e.c;
>+ for (;;)
>+ {
>+ int *a = h->a, i;
>+ for (i = x; i; i--)
>+ bar (a[f]);
>+ bar (a[f]);
>+ }
>+}
>
> Jakub
