[gcc r9-9908] tree-optimization/97953 - fix bougs range recorded by EVRP

[Richard Biener]

https://gcc.gnu.org/g:c018cf9d12c5909a852c33a200cf816204c219b3

commit r9-9908-gc018cf9d12c5909a852c33a200cf816204c219b3
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Nov 26 16:13:08 2020 +0100

    tree-optimization/97953 - fix bougs range recorded by EVRP
    
    EVRP records some ranges from asserts into SSA_NAME_RANGE_INFO
    but fails to assert that the condition the range is derived from
    is always true after the SSA names definition.  The patch implements
    the simplest post-dominance check, basic-block equality.
    
    2020-11-26  Richard Biener  <rguenther@suse.de>
    
            PR tree-optimization/97953
            * gimple-ssa-evrp-analyze.c
            (evrp_range_analyzer::record_ranges_from_incoming_edge): Make
            sure the condition post-dominates the SSA definition before
            recording into SSA_NAME_RANGE_INFO.
    
            * gcc.dg/pr97953.c: New testcase.
    
    (cherry picked from commit c76b3f9e83353a4cd437ca137c1fb835c9b5c21f)

Diff:
---
 gcc/gimple-ssa-evrp-analyze.c  |  6 +++++-
 gcc/testsuite/gcc.dg/pr97953.c | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/gcc/gimple-ssa-evrp-analyze.c b/gcc/gimple-ssa-evrp-analyze.c
index bb4e2d6e798..3a6956c59c6 100644
--- a/gcc/gimple-ssa-evrp-analyze.c
+++ b/gcc/gimple-ssa-evrp-analyze.c
@@ -217,7 +217,11 @@ evrp_range_analyzer::record_ranges_from_incoming_edge (basic_block bb)
 	      push_value_range (vrs[i].first, vrs[i].second);
 	      if (is_fallthru
 		  && m_update_global_ranges
-		  && all_uses_feed_or_dominated_by_stmt (vrs[i].first, stmt))
+		  && all_uses_feed_or_dominated_by_stmt (vrs[i].first, stmt)
+		  /* The condition must post-dominate the definition point.  */
+		  && (SSA_NAME_IS_DEFAULT_DEF (vrs[i].first)
+		      || (gimple_bb (SSA_NAME_DEF_STMT (vrs[i].first))
+			  == pred_e->src)))
 		{
 		  set_ssa_range_info (vrs[i].first, vrs[i].second);
 		  maybe_set_nonzero_bits (pred_e, vrs[i].first);
diff --git a/gcc/testsuite/gcc.dg/pr97953.c b/gcc/testsuite/gcc.dg/pr97953.c
new file mode 100644
index 00000000000..6219619d67b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr97953.c
@@ -0,0 +1,24 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-tree-fre" } */
+
+int __attribute__((noipa))
+foo (int flag, int *p)
+{
+  int val = *p;
+  if (flag)
+    {
+      if (val != 1)
+        __builtin_unreachable ();
+      return 0;
+    }
+  int val2 = *p;
+  return val2 == 2;
+}
+
+int main()
+{
+  int i = 2;
+  if (foo (0, &i) != 1)
+    __builtin_abort ();
+  return 0;
+}