In dominates() there is the following comment:
"We don't think two explicitly different symbols ever alias"
but the corresponding test only check if the storage in the
potentialy dominating instruction is a symbol and if so returns 0
meaning that it can't dominate.
But that's without taking in account that a pointer can point
to this symbol and thus that a store via this symbol can dominate
a store via a pointer.
Fix this by changing the test more in accordance to the comment:
return 0 only if the 2 concerned location correspond to 2 *distinct*
symbols (and thus do not return 0 if one of the location is not a symbol).
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
flow.c | 11 ++++++++++-
validation/alias-distinct.c | 17 +++++++++++++++++
validation/alias-mixed.c | 30 ++++++++++++++++++++++++++++++
validation/alias-same.c | 17 +++++++++++++++++
4 files changed, 74 insertions(+), 1 deletion(-)
create mode 100644 validation/alias-distinct.c
create mode 100644 validation/alias-mixed.c
create mode 100644 validation/alias-same.c
diff --git a/flow.c b/flow.c
index 94a8ec746..4b32f5cc8 100644
--- a/flow.c
+++ b/flow.c
@@ -314,6 +314,15 @@ static inline int same_memop(struct instruction *a, struct instruction *b)
return a->offset == b->offset && a->size == b->size;
}
+static inline int distinct_symbols(pseudo_t a, pseudo_t b)
+{
+ if (a->type != PSEUDO_SYM)
+ return 0;
+ if (b->type != PSEUDO_SYM)
+ return 0;
+ return a->sym != b->sym;
+}
+
/*
* Return 1 if "dom" dominates the access to "pseudo"
* in "insn".
@@ -332,7 +341,7 @@ int dominates(pseudo_t pseudo, struct instruction *insn, struct instruction *dom
if (local)
return 0;
/* We don't think two explicitly different symbols ever alias */
- if (dom->src->type == PSEUDO_SYM)
+ if (distinct_symbols(insn->src, dom->src))
return 0;
/* We could try to do some alias analysis here */
return -1;
diff --git a/validation/alias-distinct.c b/validation/alias-distinct.c
new file mode 100644
index 000000000..42937b24b
--- /dev/null
+++ b/validation/alias-distinct.c
@@ -0,0 +1,17 @@
+extern int g;
+extern int h;
+
+static int foo(void)
+{
+ g = 1;
+ h = 2;
+ return g == 1;
+}
+
+/*
+ * check-name: alias distinct symbols
+ * check-command: test-linearize $file
+ * check-output-ignore
+ *
+ * check-output-contains: ret\\..* *\\$1
+ */
diff --git a/validation/alias-mixed.c b/validation/alias-mixed.c
new file mode 100644
index 000000000..429304774
--- /dev/null
+++ b/validation/alias-mixed.c
@@ -0,0 +1,30 @@
+extern int g;
+
+
+static int foo(int *p)
+{
+ *p = 1;
+ g = 2;
+ return *p == 1;
+}
+
+static int bar(int *p)
+{
+ g = 1;
+ *p = 2;
+ return g == 1;
+}
+
+static test(void)
+{
+ foo(&g);
+ bar(&g);
+}
+
+/*
+ * check-name: alias symbol/pointer
+ * check-command: test-linearize $file
+ * check-output-ignore
+ *
+ * check-output-excludes: ret\\..* *\\$1
+ */
diff --git a/validation/alias-same.c b/validation/alias-same.c
new file mode 100644
index 000000000..55cf42445
--- /dev/null
+++ b/validation/alias-same.c
@@ -0,0 +1,17 @@
+extern int g;
+
+
+static int foo(void)
+{
+ g = 1;
+ g = 2;
+ return g != 1;
+}
+
+/*
+ * check-name: alias same symbols
+ * check-command: test-linearize $file
+ * check-output-ignore
+ *
+ * check-output-contains: ret\\..* *\\$1
+ */
--
2.12.2
--
To unsubscribe from this list: send the line "unsubscribe linux-sparse" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
