[gcc(refs/users/aoliva/heads/testme)] [ifcombine] avoid bitfield refs that could trap [PR118514]

[Alexandre Oliva via Gcc-cvs]

https://gcc.gnu.org/g:58dbf143f4d724222c754766d4957f5e099244d9

commit 58dbf143f4d724222c754766d4957f5e099244d9
Author: Alexandre Oliva <ol...@gnu.org>
Date:   Sat Jan 18 00:40:51 2025 -0300

    [ifcombine] avoid bitfield refs that could trap [PR118514]

Diff:
---
 gcc/gimple-fold.cc                    | 13 +++++++++----
 gcc/testsuite/gcc.dg/field-merge-23.c | 19 +++++++++++++++++++
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 3c971a29ef04..612810c35b08 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -7686,10 +7686,10 @@ decode_field_reference (tree *pexp, HOST_WIDE_INT 
*pbitsize,
       || bs <= shiftrt
       || offset != 0
       || TREE_CODE (inner) == PLACEHOLDER_EXPR
-      /* Reject out-of-bound accesses (PR79731).  */
-      || (! AGGREGATE_TYPE_P (TREE_TYPE (inner))
-         && compare_tree_int (TYPE_SIZE (TREE_TYPE (inner)),
-                              bp + bs) < 0)
+      /* Reject out-of-bound accesses (PR79731, PR118514).  */
+      || !tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (inner)))
+      || compare_tree_int (TYPE_SIZE (TREE_TYPE (inner)),
+                          bp + bs) < 0
       || (INTEGRAL_TYPE_P (TREE_TYPE (inner))
          && !type_has_mode_precision_p (TREE_TYPE (inner))))
     return NULL_TREE;
@@ -7859,6 +7859,11 @@ make_bit_field_load (location_t loc, tree inner, tree 
orig_inner, tree type,
       gimple *new_stmt = gsi_stmt (i);
       if (gimple_has_mem_ops (new_stmt))
        gimple_set_vuse (new_stmt, reaching_vuse);
+      gcc_checking_assert (! (gimple_assign_load_p (point)
+                             && gimple_assign_load_p (new_stmt))
+                          || (tree_could_trap_p (gimple_assign_rhs1 (point))
+                              == tree_could_trap_p (gimple_assign_rhs1
+                                                    (new_stmt))));
     }
 
   gimple_stmt_iterator gsi = gsi_for_stmt (point);
diff --git a/gcc/testsuite/gcc.dg/field-merge-23.c 
b/gcc/testsuite/gcc.dg/field-merge-23.c
new file mode 100644
index 000000000000..96604d43c9de
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/field-merge-23.c
@@ -0,0 +1,19 @@
+/* { dg-do run } */
+/* { dg-options "-O" } */
+
+/* PR tree-optimization/118514 */
+
+/* Check that we don't create BIT_FIELD_REFs that could trap, because they are
+   assumed not to trap and could be pulled out of loops.  */
+
+int a, c = 1;
+unsigned char b[1], d;
+int main() {
+  while (a || !c) {
+    signed char e = b[1000000000];
+    d = e < 0 || b[1000000000] > 1;
+    if (d)
+      __builtin_abort ();
+  }
+  return 0;
+}