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?
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
