On 6/21/19 6:28 AM, Richard Biener wrote:
> On Fri, Jun 21, 2019 at 12:24 AM Jeff Law <l...@redhat.com> wrote:
>>
>> As outlined in the BZ, our alias analysis code is context insensitive.
>> So when we copy-propagate pointers, we can can and do copy PTA
>> information from members to the representative pointer in the copy-of
>> chain (we do this when the representative pointer has no associated PTA
>> information).
>>
>> However, [E]VRP can set the non-nullness of a pointer using context
>> sensitive information. So we have to be more careful when copying PTA
>> information.
>>
>> We already have similar issues with alignment information as well. This
>> patch just extends the hack to avoid copying alignment information in
>> some circumstances to also avoid copying the non-nullness property.
>>
>> Bootstrapped and regression tested on x86_64-linux-gnu. OK for the trunk?
>
> I think this should be done in reset_flow_sensitive_info () as well
> and tree-ssa-copy.c should use that function instead of calling
> mark_ptr_info_alignment_unknown.
>
> I'd probably avoid the new clear_ptr_nonnull function since it might make
> people miss the other half (alignment).
>
> Otherwise looks OK.
Given that reset_flow_sensitive_info is used in a variety of other
places, the requested changes seemed well past the line that required
another bootstrap & regression test, which went fine.
Attached is what I actually installed. I'll backport to gcc-9 after a
few days. I'll need to look at a gcc-8 to see if it's potentially
needed there as well.
jeff
* gcc.c-torture/execute/pr90949.c: New test.
* tree-ssa-copy.c (fini_copy_prop): Use reset_flow_sensitive_info.
* tree-ssanames.c (reset_flow_sensitive_info): Reset non-null state.
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr90949.c
b/gcc/testsuite/gcc.c-torture/execute/pr90949.c
new file mode 100644
index 00000000000..8c2ae3972d4
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr90949.c
@@ -0,0 +1,42 @@
+void __attribute__ ((noipa, noinline)) my_puts (const char *str) { }
+
+void __attribute__ ((noipa, noinline)) my_free (void *p) { }
+
+
+struct Node
+{
+ struct Node *child;
+};
+
+struct Node space[2] = { };
+
+struct Node * __attribute__ ((noipa, noinline)) my_malloc (int bytes)
+{
+ return &space[0];
+}
+
+void
+walk (struct Node *module, int cleanup)
+{
+ if (module == 0)
+ {
+ return;
+ }
+ if (!cleanup)
+ {
+ my_puts ("No cleanup");
+ }
+ walk (module->child, cleanup);
+ if (cleanup)
+ {
+ my_free (module);
+ }
+}
+
+int
+main ()
+{
+ struct Node *node = my_malloc (sizeof (struct Node));
+ node->child = 0;
+ walk (node, 1);
+}
diff --git a/gcc/tree-ssa-copy.c b/gcc/tree-ssa-copy.c
index 89532633e42..28ff8d3fbe2 100644
--- a/gcc/tree-ssa-copy.c
+++ b/gcc/tree-ssa-copy.c
@@ -545,13 +545,12 @@ fini_copy_prop (void)
duplicate_ssa_name_ptr_info (copy_of[i].value,
SSA_NAME_PTR_INFO (var));
/* Points-to information is cfg insensitive,
- but alignment info might be cfg sensitive, if it
- e.g. is derived from VRP derived non-zero bits.
- So, do not copy alignment info if the two SSA_NAMEs
- aren't defined in the same basic block. */
+ but [E]VRP might record context sensitive alignment
+ info, non-nullness, etc. So reset context sensitive
+ info if the two SSA_NAMEs aren't defined in the same
+ basic block. */
if (var_bb != copy_of_bb)
- mark_ptr_info_alignment_unknown
- (SSA_NAME_PTR_INFO (copy_of[i].value));
+ reset_flow_sensitive_info (copy_of[i].value);
}
else if (!POINTER_TYPE_P (TREE_TYPE (var))
&& SSA_NAME_RANGE_INFO (var)
diff --git a/gcc/tree-ssanames.c b/gcc/tree-ssanames.c
index 5bac799e9a3..8b80bce8945 100644
--- a/gcc/tree-ssanames.c
+++ b/gcc/tree-ssanames.c
@@ -820,7 +820,12 @@ reset_flow_sensitive_info (tree name)
{
/* points-to info is not flow-sensitive. */
if (SSA_NAME_PTR_INFO (name))
- mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (name));
+ {
+ /* [E]VRP can derive context sensitive alignment info and
+ non-nullness properties. We must reset both. */
+ mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (name));
+ SSA_NAME_PTR_INFO (name)->pt.null = 1;
+ }
}
else
SSA_NAME_RANGE_INFO (name) = NULL;
