An expression like "x == 0/0" does not test any actual bits in field x,
so it resolves to true, but expr_simplify() was not smart enough to see
this.
This goes beyond an optimization, to become a bug fix, because
expr_normalize() will assert-fail for expressions that become trivial
when this simplification is omitted. For example:
$ echo 'eth.dst == 0/0 && eth.dst == 0/0' | tests/ovstest test-ovn
normalize-expr
test-ovn: ../include/openvswitch/list.h:245: assertion
!ovs_list_is_empty(list) failed in ovs_list_front()
Aborted (core dumped)
This commit fixes this and related problems.
The test added by this commit is very specific to the particular problem,
whereas a more general test would be better. A later commit adds the
general test.
Signed-off-by: Ben Pfaff <b...@ovn.org>
---
ovn/lib/expr.c | 15 ++++++++++++++-
tests/ovn.at | 8 ++++++++
2 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/ovn/lib/expr.c b/ovn/lib/expr.c
index 4ae6b0b..a5dbcfa 100644
--- a/ovn/lib/expr.c
+++ b/ovn/lib/expr.c
@@ -1669,6 +1669,18 @@ expr_annotate(struct expr *expr, const struct shash
*symtab, char **errorp)
}
static struct expr *
+expr_simplify_eq(struct expr *expr)
+{
+ const union mf_subvalue *mask = &expr->cmp.mask;
+ if (is_all_zeros(mask, sizeof *mask)) {
+ /* Simplify "ip4.dst == 0/0" to just "1" (plus a prerequisite). */
+ expr_destroy(expr);
+ return expr_create_boolean(true);
+ }
+ return expr;
+}
+
+static struct expr *
expr_simplify_ne(struct expr *expr)
{
struct expr *new = NULL;
@@ -1742,7 +1754,8 @@ expr_simplify(struct expr *expr)
switch (expr->type) {
case EXPR_T_CMP:
- return (expr->cmp.relop == EXPR_R_EQ || !expr->cmp.symbol->width ? expr
+ return (!expr->cmp.symbol->width ? expr
+ : expr->cmp.relop == EXPR_R_EQ ? expr_simplify_eq(expr)
: expr->cmp.relop == EXPR_R_NE ? expr_simplify_ne(expr)
: expr_simplify_relational(expr));
diff --git a/tests/ovn.at b/tests/ovn.at
index 8be774e..b2808e2 100644
--- a/tests/ovn.at
+++ b/tests/ovn.at
@@ -425,6 +425,14 @@ AT_CHECK([ovstest test-ovn exhaustive --operation=simplify
--nvars=1 --svars=1 3
])
AT_CLEANUP
+AT_SETUP([ovn -- simplification special cases])
+simplify() {
+ echo "$1" | ovstest test-ovn simplify-expr
+}
+AT_CHECK([simplify 'eth.dst == 0/0'], [0], [1
+])
+AT_CLEANUP
+
AT_SETUP([ovn -- 4-term numeric expression normalization])
AT_CHECK([ovstest test-ovn exhaustive --operation=normalize --nvars=3
--svars=0 --bits=1 4], [0],
[Tested normalizing 1207162 expressions of 4 terminals with 3 numeric vars
(each 1 bits) in terms of operators == != < <= > >=.
--
2.1.3
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