[gcc r13-2305] tree-optimization/65244 - include asserts in predicates for uninit

[gcc r13-2305] tree-optimization/65244 - include asserts in predicates for uninit

[Richard Biener]

https://gcc.gnu.org/g:40f347881ade08fe9c0f8b527f8b54bd53aed195

commit r13-2305-g40f347881ade08fe9c0f8b527f8b54bd53aed195
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Aug 30 10:31:26 2022 +0200

    tree-optimization/65244 - include asserts in predicates for uninit
    
    When uninit computes the actual predicates from the control dependence
    edges it currently skips those that are assert-like (where one edge
    leads to a block which ends in a noreturn call).  That leads to
    bogus uninit diagnostics when applied on the USE side.
    
            PR tree-optimization/65244
            * gimple-predicate-analysis.h (predicate::init_from_control_deps):
            Add argument to specify whether the predicate is for the USE.
            * gimple-predicate-analysis.cc (predicate::init_from_control_deps):
            Also include predicates effective fallthru control edges when
            the predicate is for the USE.
    
            * gcc.dg/uninit-pr65244-2.c: New testcase.

Diff:
---
 gcc/gimple-predicate-analysis.cc        | 17 +++++++++++------
 gcc/gimple-predicate-analysis.h         |  2 +-
 gcc/testsuite/gcc.dg/uninit-pr65244-2.c | 20 ++++++++++++++++++++
 3 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/gcc/gimple-predicate-analysis.cc b/gcc/gimple-predicate-analysis.cc
index 6b2e347536a..49500b77832 100644
--- a/gcc/gimple-predicate-analysis.cc
+++ b/gcc/gimple-predicate-analysis.cc
@@ -1666,7 +1666,7 @@ predicate::normalize (gimple *use_or_def, bool is_use)
 
 void
 predicate::init_from_control_deps (const vec<edge> *dep_chains,
-				   unsigned num_chains)
+				   unsigned num_chains, bool is_use)
 {
   gcc_assert (is_empty ());
 
@@ -1675,7 +1675,8 @@ predicate::init_from_control_deps (const vec<edge> *dep_chains,
     return;
 
   if (DEBUG_PREDICATE_ANALYZER && dump_file)
-    fprintf (dump_file, "init_from_control_deps {%s}:\n",
+    fprintf (dump_file, "init_from_control_deps [%s] {%s}:\n",
+	     is_use ? "USE" : "DEF",
 	     format_edge_vecs (dep_chains, num_chains).c_str ());
 
   /* Convert the control dependency chain into a set of predicates.  */
@@ -1711,8 +1712,12 @@ predicate::init_from_control_deps (const vec<edge> *dep_chains,
 	  if (is_gimple_call (cond_stmt) && EDGE_COUNT (e->src->succs) >= 2)
 	    /* Ignore EH edge.  Can add assertion on the other edge's flag.  */
 	    continue;
-	  /* Skip if there is essentially one succesor.  */
-	  if (EDGE_COUNT (e->src->succs) == 2)
+	  /* Skip this edge if it is bypassing an abort - when the
+	     condition is not satisfied we are neither reaching the
+	     definition nor the use so it isn't meaningful.  Note if
+	     we are processing the use predicate the condition is
+	     meaningful.  See PR65244.  */
+	  if (!is_use && EDGE_COUNT (e->src->succs) == 2)
 	    {
 	      edge e1;
 	      edge_iterator ei1;
@@ -1941,7 +1946,7 @@ uninit_analysis::init_use_preds (predicate &use_preds, basic_block def_bb,
      condition under which the definition in DEF_BB is used in USE_BB.
      Each OR subexpression is represented by one element of DEP_CHAINS,
      where each element consists of a series of AND subexpressions.  */
-  use_preds.init_from_control_deps (dep_chains, num_chains);
+  use_preds.init_from_control_deps (dep_chains, num_chains, true);
   return !use_preds.is_empty ();
 }
 
@@ -2050,7 +2055,7 @@ uninit_analysis::init_from_phi_def (gphi *phi)
   /* Convert control dependence chains to the predicate in *THIS under
      which the PHI operands are defined to values for which M_EVAL is
      false.  */
-  m_phi_def_preds.init_from_control_deps (dep_chains, num_chains);
+  m_phi_def_preds.init_from_control_deps (dep_chains, num_chains, false);
   return !m_phi_def_preds.is_empty ();
 }
 
diff --git a/gcc/gimple-predicate-analysis.h b/gcc/gimple-predicate-analysis.h
index 48da8f70efd..bc0248d7a93 100644
--- a/gcc/gimple-predicate-analysis.h
+++ b/gcc/gimple-predicate-analysis.h
@@ -65,7 +65,7 @@ class predicate
     return m_preds;
   }
 
-  void init_from_control_deps (const vec<edge> *, unsigned);
+  void init_from_control_deps (const vec<edge> *, unsigned, bool);
 
   void dump (gimple *, const char *) const;
 
diff --git a/gcc/testsuite/gcc.dg/uninit-pr65244-2.c b/gcc/testsuite/gcc.dg/uninit-pr65244-2.c
new file mode 100644
index 00000000000..a28893cdcb5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-pr65244-2.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-Og -Wuninitialized -ftree-bit-ccp -fno-thread-jumps -fdump-tree-uninit2" } */
+
+void exit(int __status) __attribute__ ((__noreturn__));
+int posix_memalign(void **__memptr, __SIZE_TYPE__ __alignment,
+		   __SIZE_TYPE__ __size);
+
+void *f(void)
+{
+  void *ptr;
+
+  if (posix_memalign(&ptr, 16, 256) != 0)
+    exit(1);
+
+  return ptr; /* { dg-bogus "uninitialized" } */
+}
+
+/* Make sure the uninit pass has something to do, add to the set of
+   disabled optimizations if not.  */
+/* { dg-final { scan-tree-dump "# ptr_. = PHI" "uninit2" } } */