PR analyzer/115564 reports a missing warning from the analyzer
on this infinite loop at -O2 and above:
void test (unsigned b)
{
for (unsigned i = b; i >= 0; --i) {}
}
The issue is that there are no useful location_t values in the CFG
by the time the analyzer sees it: two basic blocks with no
statements, connected by edges with UNKNOWN_LOCATION for their
"goto_locus" values. The analyzer's attempts to get a location for the
loop fail with "UNKNOWN_LOCATION", and so it gives up on the warning.
Root cause is that the edge in question is created by gimple_split_edge
within the loop optimizer, and gimple_split_edge creates the new edge
with UNKNOWN_LOCATION.
This patch tweaks gimple_split_edge to copy edge_in->goto_locus's to the
new edge, so that the edge seen by the analyzer has a useful goto_locus
value, fixing the issue.
Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
Successful run of analyzer integration tests on x86_64-pc-linux-gnu,
which shows 8 new true positives from -Wanalyzer-infinite-loop with
the patch.
OK for trunk?
gcc/testsuite/ChangeLog:
PR analyzer/115564
* c-c++-common/analyzer/infinite-loop-pr115564.c: New test.
gcc/ChangeLog:
PR analyzer/115564
* tree-cfg.cc (gimple_split_edge): Propagate any source location
from EDGE_IN to the new edge.
Signed-off-by: David Malcolm <dmalc...@redhat.com>
---
.../c-c++-common/analyzer/infinite-loop-pr115564.c | 8 ++++++++
gcc/tree-cfg.cc | 3 +++
2 files changed, 11 insertions(+)
create mode 100644 gcc/testsuite/c-c++-common/analyzer/infinite-loop-pr115564.c
diff --git a/gcc/testsuite/c-c++-common/analyzer/infinite-loop-pr115564.c
b/gcc/testsuite/c-c++-common/analyzer/infinite-loop-pr115564.c
new file mode 100644
index 000000000000..950d92dd1254
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/analyzer/infinite-loop-pr115564.c
@@ -0,0 +1,8 @@
+/* Verify that we detect the infinite loop below even at -O2. */
+
+/* { dg-additional-options "-O2" } */
+
+void test (unsigned b)
+{
+ for (unsigned i = b; i >= 0; --i) {} /* { dg-warning "infinite loop" } */
+}
diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index 7fb7b92966be..45c0eef6c095 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -3061,6 +3061,9 @@ gimple_split_edge (edge edge_in)
/* set_phi_nodes sets the BB of the PHI nodes, so do it manually here. */
dest->il.gimple.phi_nodes = saved_phis;
+ /* Propagate any source location from EDGE_IN to the new edge. */
+ new_edge->goto_locus = edge_in->goto_locus;
+
return new_bb;
}
--
2.26.3
