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Re: [PATCH] Unshare constants in the constant pool (PR target/42894)
On Thu, Jan 27, 2011 at 09:48:00AM +0100, Jakub Jelinek wrote:
> On Wed, Jan 26, 2011 at 06:29:25PM -0700, Jeff Law wrote:
> > Well, one could easily argue that using the original expression in the
> > REG_EQUAL note is incorrect as well. In fact, looking over all the
> > calls to set_unique_reg_note shows that most either copy the value or
> > generate a new one.
> >
> > I think that means we actually want both the varasm.c and the expr.c
> > change to avoid incorrect sharing.
>
> I think the reason why most of the set_unique_reg_note calls copy_rtx
> is that the pattern is usually kept in the insn (or in some other insn).
> In the emit_move_insn case it specifically tests that the pattern is not
> there (well, some weird target could embed it in some unspec or something),
> the reason I changed force_const_mem was to deal with any other uses of
> force_const_mem.
>
> But I guess if you strongly prefer to have it in both places I can test a
> patch.
This passed bootstrap/regtest on x86_64-linux and i686-linux too:
2011-01-27 Jakub Jelinek <jakub@redhat.com>
PR target/42894
* varasm.c (force_const_mem): Store copy of x in desc->constant
instead of x itself.
* expr.c (emit_move_insn): Add a copy of y_cst instead of y_cst
itself into REG_EQUAL note.
* gcc.dg/tls/pr42894.c: New test.
--- gcc/varasm.c.jj 2011-01-25 12:58:41.000000000 +0100
+++ gcc/varasm.c 2011-01-26 14:07:50.635389932 +0100
@@ -3518,7 +3518,7 @@ force_const_mem (enum machine_mode mode,
pool->offset &= ~ ((align / BITS_PER_UNIT) - 1);
desc->next = NULL;
- desc->constant = tmp.constant;
+ desc->constant = copy_rtx (tmp.constant);
desc->offset = pool->offset;
desc->hash = hash;
desc->mode = mode;
--- gcc/expr.c.jj 2011-01-26 14:07:50.635389932 +0100
+++ gcc/expr.c 2011-01-27 17:05:04.936795133 +0100
@@ -3398,7 +3398,7 @@ emit_move_insn (rtx x, rtx y)
&& (set = single_set (last_insn)) != NULL_RTX
&& SET_DEST (set) == x
&& ! rtx_equal_p (y_cst, SET_SRC (set)))
- set_unique_reg_note (last_insn, REG_EQUAL, y_cst);
+ set_unique_reg_note (last_insn, REG_EQUAL, copy_rtx (y_cst));
return last_insn;
}
--- gcc/testsuite/gcc.dg/tls/pr42894.c.jj 2011-01-26 16:29:13.765389223 +0100
+++ gcc/testsuite/gcc.dg/tls/pr42894.c 2011-01-26 16:31:46.830433380 +0100
@@ -0,0 +1,12 @@
+/* PR target/42894 */
+/* { dg-do compile } */
+/* { dg-options "-march=armv5te -mthumb" { target arm*-*-* } } */
+/* { dg-require-effective-target tls } */
+
+extern __thread int t;
+
+void
+foo (int a)
+{
+ t = a;
+}
Jakub