On Tue, 4 Mar 2014, Jakub Jelinek wrote:
> Hi!
>
> As discussed in the PR, the assumption that in !optimize functions
> all SSA_NAMEs for a particular PARM_DECL or RESULT_DECL can be coalesced
> together is wrong for -flto, if you compile with optimizations the object
> file and then link with -O0 -flto, because the SSA_NAMEs can already
> overlap.
>
> As we don't have info right now if a particular function has always been
> compiled with !optimize during the LTO pipeline, this patch fixes the
> wrong-code by always assuming it might be optimized at some point if
> in_lto_p.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok.
Thanks,
Richard.
> 2014-03-04 Jakub Jelinek <ja...@redhat.com>
>
> PR lto/60404
> * cfgexpand.c (expand_used_vars): Do not assume all SSA_NAMEs
> of PARM/RESULT_DECLs must be coalesced with optimize && in_lto_p.
> * tree-ssa-coalesce.c (coalesce_ssa_name): Use MUST_COALESCE_COST - 1
> cost for in_lto_p.
>
> * gcc.dg/lto/pr60404_0.c: New test.
> * gcc.dg/lto/pr60404_1.c: New file.
> * gcc.dg/lto/pr60404_2.c: New file.
>
> --- gcc/cfgexpand.c.jj 2014-03-04 10:57:18.000000000 +0100
> +++ gcc/cfgexpand.c 2014-03-04 11:12:12.684524383 +0100
> @@ -1652,10 +1652,12 @@ expand_used_vars (void)
> debug info, there is no need to do so if optimization is disabled
> because all the SSA_NAMEs based on these DECLs have been coalesced
> into a single partition, which is thus assigned the canonical RTL
> - location of the DECLs. */
> + location of the DECLs. If in_lto_p, we can't rely on optimize,
> + a function could be compiled with -O1 -flto first and only the
> + link performed at -O0. */
> if (TREE_CODE (SSA_NAME_VAR (var)) == VAR_DECL)
> expand_one_var (var, true, true);
> - else if (DECL_IGNORED_P (SSA_NAME_VAR (var)) || optimize)
> + else if (DECL_IGNORED_P (SSA_NAME_VAR (var)) || optimize || in_lto_p)
> {
> /* This is a PARM_DECL or RESULT_DECL. For those partitions that
> contain the default def (representing the parm or result itself)
> --- gcc/tree-ssa-coalesce.c.jj 2014-01-03 11:40:57.000000000 +0100
> +++ gcc/tree-ssa-coalesce.c 2014-03-04 11:15:46.955296026 +0100
> @@ -1289,9 +1289,12 @@ coalesce_ssa_name (void)
> _require_ that all the names originating from it be
> coalesced, because there must be a single partition
> containing all the names so that it can be assigned
> - the canonical RTL location of the DECL safely. */
> + the canonical RTL location of the DECL safely.
> + If in_lto_p, a function could have been compiled
> + originally with optimizations and only the link
> + performed at -O0, so we can't actually require it. */
> const int cost
> - = TREE_CODE (SSA_NAME_VAR (a)) == VAR_DECL
> + = (TREE_CODE (SSA_NAME_VAR (a)) == VAR_DECL || in_lto_p)
> ? MUST_COALESCE_COST - 1 : MUST_COALESCE_COST;
> add_coalesce (cl, SSA_NAME_VERSION (a),
> SSA_NAME_VERSION (*slot), cost);
> --- gcc/testsuite/gcc.dg/lto/pr60404_0.c.jj 2014-03-04 11:19:48.503909557
> +0100
> +++ gcc/testsuite/gcc.dg/lto/pr60404_0.c 2014-03-04 11:09:51.590333222
> +0100
> @@ -0,0 +1,15 @@
> +/* { dg-lto-do run } */
> +/* { dg-lto-options { { -O1 -flto } } } */
> +/* { dg-extra-ld-options { -O0 } } */
> +
> +extern void fn2 (int);
> +int a[1], b;
> +
> +int
> +main ()
> +{
> + fn2 (0);
> + if (b != 0 || a[b] != 0)
> + __builtin_abort ();
> + return 0;
> +}
> --- gcc/testsuite/gcc.dg/lto/pr60404_1.c.jj 2014-03-04 11:19:51.057894910
> +0100
> +++ gcc/testsuite/gcc.dg/lto/pr60404_1.c 2014-03-04 09:32:35.000000000
> +0100
> @@ -0,0 +1,4 @@
> +void
> +fn1 (int p)
> +{
> +}
> --- gcc/testsuite/gcc.dg/lto/pr60404_2.c.jj 2014-03-04 11:19:54.578874717
> +0100
> +++ gcc/testsuite/gcc.dg/lto/pr60404_2.c 2014-03-04 09:33:18.000000000
> +0100
> @@ -0,0 +1,9 @@
> +extern int b;
> +extern void fn1 (int);
> +
> +void
> +fn2 (int p)
> +{
> + b = p++;
> + fn1 (p);
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imend"orffer
