This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[PR 69355] Correct hole detection when total_scalarization fails
- From: Martin Jambor <mjambor at suse dot cz>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Cc: Richard Biener <rguenther at suse dot de>
- Date: Tue, 26 Jan 2016 18:21:31 +0100
- Subject: [PR 69355] Correct hole detection when total_scalarization fails
- Authentication-results: sourceware.org; auth=none
Hi,
PR 69355 has revealed that when SRA attempts total scalarization of an
aggregate but this fails because the user type-casts a scalar field
and stores into a it a smaller aggregate (and the scalar field is not
written to, whether directly or as a part of an aggregate store), the
pass can loose track of unscalarized data there.
I think that this can happen only when violating strict aliasing rules
but with -fno-strict-aliasing it should work.
Fixed thusly with the patch below (the condition is there to avoid
detecting padding after aggregate-fields in totally-scalarized
aggregates as unscalarized data). Bootstrapped and tested on
x86_64-linux. OK for trunk? And the gcc-5 branch?
Thanks,
Martin
2016-01-26 Martin Jambor <mjambor@suse.cz>
PR tree-optimization/69355
* tree-sra.c (analyze_access_subtree): Correct hole detection when
total_scalarization fails.
testsuite/
* gcc.dg/tree-ssa/pr69355.c: New test.
---
gcc/testsuite/gcc.dg/tree-ssa/pr69355.c | 44 +++++++++++++++++++++++++++++++++
gcc/tree-sra.c | 2 +-
2 files changed, 45 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr69355.c
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr69355.c b/gcc/testsuite/gcc.dg/tree-ssa/pr69355.c
new file mode 100644
index 0000000..f515c21
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr69355.c
@@ -0,0 +1,44 @@
+/* { dg-do run } */
+/* { dg-options "-O -fno-strict-aliasing" } */
+
+struct S
+{
+ void *a;
+ long double b;
+};
+
+struct Z
+{
+ long long l;
+ short s;
+} __attribute__((packed));
+
+struct S __attribute__((noclone, noinline))
+foo (void *v, struct Z *z)
+{
+ struct S t;
+ t.a = v;
+ *(struct Z *) &t.b = *z;
+ return t;
+}
+
+struct Z gz;
+
+int
+main (int argc, char **argv)
+{
+ struct S s;
+
+ if (sizeof (long double) < sizeof (struct Z))
+ return 0;
+
+ gz.l = 0xbeef;
+ gz.s = 0xab;
+
+ s = foo ((void *) 0, &gz);
+
+ if ((((struct Z *) &s.b)->l != gz.l)
+ || (((struct Z *) &s.b)->s != gz.s))
+ __builtin_abort ();
+ return 0;
+}
diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index 740542f..b0e737a 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -2421,7 +2421,7 @@ analyze_access_subtree (struct access *root, struct access *parent,
if (covered_to < limit)
hole = true;
- if (scalar)
+ if (scalar || !allow_replacements)
root->grp_total_scalarization = 0;
}
--
2.7.0