This is v2 which uses Richi's code.
This amends "the post-dominance check to deal with
SSA cycles [...]. We need to constrain the load to
be in the same or a subloop (use
flow_loop_nested_p, not loop depth) or in the same
BB when either the load or the PHI is in an irreducible region."
(as described by Richard).
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/116835
gcc/ChangeLog:
* tree-ssa-phiprop.cc (propagate_with_phi): Admend the
post-dom check to deal with ssa cycles.
gcc/testsuite/ChangeLog:
* gcc.dg/torture/pr116835.c: New test.
* gcc.dg/tree-ssa/phiprop-6.c: New test.
* gcc.dg/tree-ssa/phiprop-7.c: New test.
Signed-off-by: Andrew Pinski <[email protected]>
Co-authored-by: Richard Biener <[email protected]>
---
gcc/testsuite/gcc.dg/torture/pr116835.c | 33 +++++++++++++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/phiprop-6.c | 21 +++++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/phiprop-7.c | 21 +++++++++++++++
gcc/tree-ssa-phiprop.cc | 12 +++++++++
4 files changed, 87 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr116835.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phiprop-6.c
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phiprop-7.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/testsuite/gcc.dg/tree-ssa/phiprop-6.c
b/gcc/testsuite/gcc.dg/tree-ssa/phiprop-6.c
new file mode 100644
index 00000000000..8561cd14480
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phiprop-6.c
@@ -0,0 +1,21 @@
+/* { dg-do compile { target { weak_undefined } } } */
+/* { dg-options "-O2 -fdump-tree-phiprop-details" } */
+/* { dg-add-options weak_undefined } */
+
+/* PR tree-optimization/116835 */
+
+extern int a __attribute__((weak));
+int b;
+
+int
+bar (int c)
+{
+ int *p = &a;
+ for (int j = 0; j < c; ++j)
+ p = &b;
+ return *p;
+}
+/* The weak load is conditional with the loop so we cannot make it
unconditional. */
+/* { dg-final { scan-tree-dump-not "Removing dead stmt:" "phiprop1"} } */
+/* { dg-final { scan-tree-dump-not "Inserting PHI for result of load"
"phiprop1"} } */
+
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phiprop-7.c
b/gcc/testsuite/gcc.dg/tree-ssa/phiprop-7.c
new file mode 100644
index 00000000000..ebce03ea630
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phiprop-7.c
@@ -0,0 +1,21 @@
+/* { dg-do compile { target { weak_undefined } } } */
+/* { dg-options "-O2 -fdump-tree-phiprop-details" } */
+/* { dg-add-options weak_undefined } */
+
+/* PR tree-optimization/116835 */
+
+extern int a __attribute__((weak));
+int b;
+
+int
+bar (int c)
+{
+ int *p = &a;
+ for (int j = 0; j < *p; ++j)
+ p = &b;
+ return *p;
+}
+/* The weak load is unconditional due to the conditional so we can remove it
unconditionally. */
+/* { dg-final { scan-tree-dump "Removing dead stmt:" "phiprop1"} } */
+/* { dg-final { scan-tree-dump "Inserting PHI for result of load" "phiprop1"}
} */
+
diff --git a/gcc/tree-ssa-phiprop.cc b/gcc/tree-ssa-phiprop.cc
index a2e039fb72d..d24613d5893 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
@@ -348,6 +349,17 @@ propagate_with_phi (basic_block bb, gphi *vphi, gphi *phi,
bb, gimple_bb (use_stmt)))
delay = true;
+ /* Amend the post-dominance check for SSA cycles, we need to
+ make sure each PHI result value is dereferenced.
+ We only want to delay this if we don't insert a phi. */
+ if (!(gimple_bb (use_stmt) == bb
+ || (!(bb->flags & BB_IRREDUCIBLE_LOOP)
+ && !(gimple_bb (use_stmt)->flags & BB_IRREDUCIBLE_LOOP)
+ && (bb->loop_father == gimple_bb (use_stmt)->loop_father
+ || flow_loop_nested_p (bb->loop_father,
+ gimple_bb
(use_stmt)->loop_father)))))
+ delay = true;
+
/* Check whether this is a load of *ptr. */
if (!(is_gimple_assign (use_stmt)
&& gimple_assign_rhs_code (use_stmt) == MEM_REF
--
2.43.0
