[gcc r14-9565] middle-end/113396 - int128 array index and value-ranges

[gcc r14-9565] middle-end/113396 - int128 array index and value-ranges

[Richard Biener]

https://gcc.gnu.org/g:6a55e39bdb1fdb570730c08413ebbe744e493411

commit r14-9565-g6a55e39bdb1fdb570730c08413ebbe744e493411
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Mar 19 15:25:16 2024 +0100

    middle-end/113396 - int128 array index and value-ranges
    
    The following fixes bogus truncation of a value-range for an int128
    array index when computing the maximum extent for a variable array
    reference.  Instead of possibly slowing things down by using
    widest_int the following makes sure the range bounds fit within
    the constraints offset_int were designed for.
    
            PR middle-end/113396
            * tree-dfa.cc (get_ref_base_and_extent): Use index range
            bounds only if they fit within the address-range constraints
            of offset_int.
    
            * gcc.dg/torture/pr113396.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr113396.c | 19 +++++++++++++++++++
 gcc/tree-dfa.cc                         |  6 ++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr113396.c b/gcc/testsuite/gcc.dg/torture/pr113396.c
new file mode 100644
index 00000000000..585f717bdda
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr113396.c
@@ -0,0 +1,19 @@
+/* { dg-do run } */
+/* { dg-require-effective-target int128 } */
+
+unsigned char m[] = {5, 79, 79, 79, 79};
+__int128 p;
+int main()
+{
+  int g1 = 0;
+  p = 0;
+  for (int aj = 0; aj < 256; aj++)
+   {
+      m[0] = -4;
+      for (; p >= 0; p -= 1) {
+        g1 = m[p];
+      }
+  }
+  if (g1 != 0xfc)
+    __builtin_abort();
+}
diff --git a/gcc/tree-dfa.cc b/gcc/tree-dfa.cc
index cbd3774b21f..93e53b29a6d 100644
--- a/gcc/tree-dfa.cc
+++ b/gcc/tree-dfa.cc
@@ -549,7 +549,8 @@ get_ref_base_and_extent (tree exp, poly_int64 *poffset,
 		    /* Try to constrain maxsize with range information.  */
 		    offset_int omax
 		      = offset_int::from (max, TYPE_SIGN (TREE_TYPE (index)));
-		    if (known_lt (lbound, omax))
+		    if (wi::get_precision (max) <= ADDR_MAX_BITSIZE
+			&& known_lt (lbound, omax))
 		      {
 			poly_offset_int rmaxsize;
 			rmaxsize = (omax - lbound + 1)
@@ -567,7 +568,8 @@ get_ref_base_and_extent (tree exp, poly_int64 *poffset,
 		    /* Try to adjust bit_offset with range information.  */
 		    offset_int omin
 		      = offset_int::from (min, TYPE_SIGN (TREE_TYPE (index)));
-		    if (known_le (lbound, omin))
+		    if (wi::get_precision (min) <= ADDR_MAX_BITSIZE
+			&& known_le (lbound, omin))
 		      {
 			poly_offset_int woffset
 			  = wi::sext (omin - lbound,