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authorMartin Jambor <mjambor@suse.cz>2020-09-03 22:43:49 +0200
committerMartin Jambor <mjambor@suse.cz>2020-09-03 22:43:49 +0200
commit8ad3fc6ca46c603d9c3efe8e6d4a8f2ff1a893a4 (patch)
treee98cc27d06a6779873ad9b689b774f28378975d6
parentd8f3474ff81b07fd2e758337957711db17eb801e (diff)
sra: Avoid SRAing if there is an aout-of-bounds access (PR 96820)
The testcase causes and ICE in the SRA verifier on x86_64 when compiling with -m32 because build_user_friendly_ref_for_offset looks at an out-of-bounds array_ref within an array_ref which accesses an offset which does not fit into a signed 32bit integer and turns it into an array-ref with a negative index. The best thing is probably to bail out early when encountering an out of bounds access to a local stack-allocated aggregate (and let the DSE just delete such statements) which is what the patch does. I also glanced over to the initial candidate vetting routine to make sure the size would fit into HWI and noticed that it uses unsigned variants whereas the rest of SRA operates on signed offsets and sizes (because get_ref_and_extent does) and so changed that for the sake of consistency. These ancient checks operate on sizes of types as opposed to DECLs but I hope that any issues potentially arising from that are basically hypothetical. gcc/ChangeLog: 2020-08-28 Martin Jambor <mjambor@suse.cz> PR tree-optimization/96820 * tree-sra.c (create_access): Disqualify candidates with accesses beyond the end of the original aggregate. (maybe_add_sra_candidate): Check that candidate type size fits signed uhwi for the sake of consistency. gcc/testsuite/ChangeLog: 2020-08-28 Martin Jambor <mjambor@suse.cz> PR tree-optimization/96820 * gcc.dg/tree-ssa/pr96820.c: New test.
-rw-r--r--gcc/testsuite/gcc.dg/tree-ssa/pr96820.c12
-rw-r--r--gcc/tree-sra.c9
2 files changed, 19 insertions, 2 deletions
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96820.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96820.c
new file mode 100644
index 00000000000..f5c2195f310
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96820.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O1" } */
+
+struct a {
+ int b;
+};
+int main() {
+ struct a d[][6] = {4};
+ struct a e;
+ d[1955249013][1955249013] = e;
+ return e.b;
+}
diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index 754f41302fc..98a6cacbe2a 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -941,6 +941,11 @@ create_access (tree expr, gimple *stmt, bool write)
disqualify_candidate (base, "Encountered an unconstrained access.");
return NULL;
}
+ if (offset + size > tree_to_shwi (DECL_SIZE (base)))
+ {
+ disqualify_candidate (base, "Encountered an access beyond the base.");
+ return NULL;
+ }
access = create_access_1 (base, offset, size);
access->expr = expr;
@@ -1880,12 +1885,12 @@ maybe_add_sra_candidate (tree var)
reject (var, "has incomplete type");
return false;
}
- if (!tree_fits_uhwi_p (TYPE_SIZE (type)))
+ if (!tree_fits_shwi_p (TYPE_SIZE (type)))
{
reject (var, "type size not fixed");
return false;
}
- if (tree_to_uhwi (TYPE_SIZE (type)) == 0)
+ if (tree_to_shwi (TYPE_SIZE (type)) == 0)
{
reject (var, "type size is zero");
return false;