[PATCH] cse: avoid signed overflow in compute_const_anchors [PR 104843]

[Xi Ruoyao via Gcc-patches]

Bootstrapped and tested on mips64el-linux-gnuabi64, and MIPS is the only
port with a non-zero targetm.const_anchor.  Ok for trunk?

-- >8 --

With a non-zero const_anchor, the behavior of this function relied on
signed overflow.

gcc/

        PR rtl-optimization/104843
        * cse.cc (compute_const_anchors): Cast to unsigned HOST_WIDE_INT
        to perform overflow arithmetics safely.
---
 gcc/cse.cc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gcc/cse.cc b/gcc/cse.cc
index a18b599d324..7c39a009449 100644
--- a/gcc/cse.cc
+++ b/gcc/cse.cc
@@ -1169,10 +1169,10 @@ compute_const_anchors (rtx cst,
                       HOST_WIDE_INT *lower_base, HOST_WIDE_INT *lower_offs,
                       HOST_WIDE_INT *upper_base, HOST_WIDE_INT *upper_offs)
 {
-  HOST_WIDE_INT n = INTVAL (cst);
+  unsigned HOST_WIDE_INT n = INTVAL (cst);
 
   *lower_base = n & ~(targetm.const_anchor - 1);
-  if (*lower_base == n)
+  if (*lower_base == INTVAL (cst))
     return false;
 
   *upper_base =
-- 
2.35.1