phiprop can sometimes prop loads back into loops
and in some cases cause wrong code when the load
was from a weak symbol as now it becomes an unconditional
load before the loop.
Bootstrapped and tested on x86_64-linux-gnu with no regressions.
PR tree-optimization/116835
gcc/ChangeLog:
* tree-ssa-phiprop.cc (propagate_with_phi): Check
the use is at the same or deeper loop depth than
the phi node.
(pass_phiprop::execute): Initialize loops.
gcc/testsuite/ChangeLog:
* gcc.dg/torture/pr116835.c: New test.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
---
gcc/testsuite/gcc.dg/torture/pr116835.c | 33 +++++++++++++++++++++++++
gcc/tree-ssa-phiprop.cc | 14 ++++++++++-
2 files changed, 46 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr116835.c
diff --git a/gcc/testsuite/gcc.dg/torture/pr116835.c
b/gcc/testsuite/gcc.dg/torture/pr116835.c
new file mode 100644
index 00000000000..31d3b59d945
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr116835.c
@@ -0,0 +1,33 @@
+/* { dg-do run { target { weak_undefined } } } */
+/* { dg-add-options weak_undefined } */
+
+/* PR tree-optimization/116835 */
+/* phiprop would prop into the loop the load of b
+ and also prop the load of a before the loop.
+ Which is incorrect as a is a weak symbol. */
+
+struct s1
+{
+ int t;
+ int t1;
+};
+typedef struct s1 type;
+extern type a __attribute__((weak));
+int t;
+type b;
+type bar (int c) __attribute__((noipa, noinline));
+type
+bar (int c)
+{
+ t = 1;
+ type *p = &a;
+ for (int j = 0; j < c; ++j)
+ p = &b;
+ return *p;
+}
+
+int main(void)
+{
+ if (bar(&a == nullptr).t)
+ __builtin_abort();
+}
diff --git a/gcc/tree-ssa-phiprop.cc b/gcc/tree-ssa-phiprop.cc
index a2e1fb16a30..c5fe231d3e9 100644
--- a/gcc/tree-ssa-phiprop.cc
+++ b/gcc/tree-ssa-phiprop.cc
@@ -35,6 +35,7 @@ along with GCC; see the file COPYING3. If not see
#include "tree-ssa-loop.h"
#include "tree-cfg.h"
#include "tree-ssa-dce.h"
+#include "cfgloop.h"
/* This pass propagates indirect loads through the PHI node for its
address to make the load source possibly non-addressable and to
@@ -348,11 +349,17 @@ propagate_with_phi (basic_block bb, gphi *phi, struct
phiprop_d *phivn,
calculate_dominance_info (CDI_POST_DOMINATORS);
/* Only replace loads in blocks that post-dominate the PHI node. That
- makes sure we don't end up speculating loads. */
+ makes sure we don't end up speculating loads. */
if (!dominated_by_p (CDI_POST_DOMINATORS,
bb, gimple_bb (use_stmt)))
continue;
+ /* Only replace loads in blocks are in the same loop
+ are inside an deeper loop. This is to make sure not
+ to prop back into the loop. */
+ if (bb_loop_depth (gimple_bb (use_stmt)) < bb_loop_depth (bb))
+ continue;
+
/* Check whether this is a load of *ptr. */
if (!(is_gimple_assign (use_stmt)
&& gimple_assign_rhs_code (use_stmt) == MEM_REF
@@ -520,6 +527,10 @@ pass_phiprop::execute (function *fun)
size_t n;
auto_bitmap dce_ssa_names;
+ /* Find the loops, so that we can prevent moving loads in
+ them. */
+ loop_optimizer_init (AVOID_CFG_MODIFICATIONS);
+
calculate_dominance_info (CDI_DOMINATORS);
n = num_ssa_names;
@@ -548,6 +559,7 @@ pass_phiprop::execute (function *fun)
free (phivn);
free_dominance_info (CDI_POST_DOMINATORS);
+ loop_optimizer_finalize ();
return did_something ? TODO_update_ssa_only_virtuals : 0;
}
--
2.43.0
