[gcc r15-7807] Fix folding of BIT_NOT_EXPR for POLY_INT_CST [PR118976]

[Richard Sandiford via Gcc-cvs]

https://gcc.gnu.org/g:78380fd7f743e23dfdf013d68a2f0347e1511550

commit r15-7807-g78380fd7f743e23dfdf013d68a2f0347e1511550
Author: Richard Sandiford <richard.sandif...@arm.com>
Date:   Tue Mar 4 10:44:35 2025 +0000

    Fix folding of BIT_NOT_EXPR for POLY_INT_CST [PR118976]
    
    There was an embarrassing typo in the folding of BIT_NOT_EXPR for
    POLY_INT_CSTs: it used - rather than ~ on the poly_int.  Not sure
    how that happened, but it might have been due to the way that
    ~x is implemented as -1 - x internally.
    
    gcc/
            PR tree-optimization/118976
            * fold-const.cc (const_unop): Use ~ rather than - for BIT_NOT_EXPR.
            * config/aarch64/aarch64.cc (aarch64_test_sve_folding): New 
function.
            (aarch64_run_selftests): Run it.

Diff:
---
 gcc/config/aarch64/aarch64.cc | 11 +++++++++++
 gcc/fold-const.cc             |  2 +-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index fe76730b0a7c..af3871ce8a1f 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -31336,6 +31336,16 @@ aarch64_test_sysreg_encoding_clashes (void)
     }
 }
 
+/* Test SVE arithmetic folding.  */
+
+static void
+aarch64_test_sve_folding ()
+{
+  tree res = fold_unary (BIT_NOT_EXPR, ssizetype,
+                        ssize_int (poly_int64 (1, 1)));
+  ASSERT_TRUE (operand_equal_p (res, ssize_int (poly_int64 (-2, -1))));
+}
+
 /* Run all target-specific selftests.  */
 
 static void
@@ -31344,6 +31354,7 @@ aarch64_run_selftests (void)
   aarch64_test_loading_full_dump ();
   aarch64_test_fractional_cost ();
   aarch64_test_sysreg_encoding_clashes ();
+  aarch64_test_sve_folding ();
 }
 
 } // namespace selftest
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index f9f7f4d2f917..fef7a6cc48ef 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -1964,7 +1964,7 @@ const_unop (enum tree_code code, tree type, tree arg0)
       if (TREE_CODE (arg0) == INTEGER_CST)
        return fold_not_const (arg0, type);
       else if (POLY_INT_CST_P (arg0))
-       return wide_int_to_tree (type, -poly_int_cst_value (arg0));
+       return wide_int_to_tree (type, ~poly_int_cst_value (arg0));
       /* Perform BIT_NOT_EXPR on each element individually.  */
       else if (TREE_CODE (arg0) == VECTOR_CST)
        {