[gcc r13-1133] match.pd: Fix up __builtin_mul_overflow_p signed type optimization [PR105984]

[gcc r13-1133] match.pd: Fix up __builtin_mul_overflow_p signed type optimization [PR105984]

[Jakub Jelinek]

https://gcc.gnu.org/g:74e6a40335765077e235269f19d2d9905d0d9e44

commit r13-1133-g74e6a40335765077e235269f19d2d9905d0d9e44
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Jun 16 14:36:04 2022 +0200

    match.pd: Fix up __builtin_mul_overflow_p signed type optimization [PR105984]
    
    Earlier in the simplification pattern, we require that @0 has compatible
    type to the type of IMAGPART_EXPR, but for @1 which is a non-zero constant
    all we require is that it the constant fits into that type.
    Later the code checks if the constant is negative, because when min / max
    values are divided by negative divisor, lo will be higher than hi.
    In the following testcase, @1 has unsigned char type, while @0 has
    int type, so @1 which is 254 is wi::neg_p and we were swapping lo and hi,
    even when @1 cast to int isn't negative.
    
    We could use tree_int_cst_sgn (@1) < 0 as the check instead and it would
    work both for narrower types of @1 and even same or wider ones, but
    I've noticed we probably don't want to call fold_convert (TREE_TYPE (@0), @1)
    twice and when we save that result in a temporary, we can just use wi::neg_p
    on that temporary.
    
    2022-06-16  Jakub Jelinek  <jakub@redhat.com>
    
            PR tree-optimization/105984
            * match.pd (__builtin_mul_overflow_p (x, cst, (stype) 0) ->
            x > stype_max / cst || x < stype_min / cst): fold_convert @1
            to TREE_TYPE (@0) just once and test for negative divisor
            also on that folded constant instead of on @1.
    
            * gcc.c-torture/execute/pr105984.c: New test.

Diff:
---
 gcc/match.pd                                   |  9 ++++-----
 gcc/testsuite/gcc.c-torture/execute/pr105984.c | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/gcc/match.pd b/gcc/match.pd
index c0aa3a2342b..ae5dc820fa5 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -6076,16 +6076,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
       (convert (eq @0 { TYPE_MIN_VALUE (TREE_TYPE (@0)); }))
       (with
        {
+	 tree div = fold_convert (TREE_TYPE (@0), @1);
 	 tree lo = int_const_binop (TRUNC_DIV_EXPR,
-				    TYPE_MIN_VALUE (TREE_TYPE (@0)),
-				    fold_convert (TREE_TYPE (@0), @1));
+				    TYPE_MIN_VALUE (TREE_TYPE (@0)), div);
 	 tree hi = int_const_binop (TRUNC_DIV_EXPR,
-				    TYPE_MAX_VALUE (TREE_TYPE (@0)),
-				    fold_convert (TREE_TYPE (@0), @1));
+				    TYPE_MAX_VALUE (TREE_TYPE (@0)), div);
 	 tree etype = range_check_type (TREE_TYPE (@0));
 	 if (etype)
 	   {
-	     if (wi::neg_p (wi::to_wide (@1)))
+	     if (wi::neg_p (wi::to_wide (div)))
 	       std::swap (lo, hi);
 	     lo = fold_convert (etype, lo);
 	     hi = fold_convert (etype, hi);
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr105984.c b/gcc/testsuite/gcc.c-torture/execute/pr105984.c
new file mode 100644
index 00000000000..9143b3d3e7e
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr105984.c
@@ -0,0 +1,19 @@
+/* PR tree-optimization/105984 */
+
+unsigned long long g;
+
+static inline unsigned long long
+foo (unsigned char c)
+{
+  g -= __builtin_mul_overflow_p (4, (unsigned char) ~c, 0);
+  return g;
+}
+
+int
+main ()
+{
+  unsigned long long x = foo (1);
+  if (x != 0)
+    __builtin_abort ();
+  return 0;
+}