lower-bitint: Fix handle_cast ICE [PR113102]

My recent change to use m_data[save_data_cnt] instead of
m_data[save_data_cnt + 1] when inside of a loop (m_bb is non-NULL)
broke the following testcase.  When we create a PHI node on the loop
using prepare_data_in_out, both m_data[save_data_cnt{, + 1}] are
computed and the fix was right, but there are also cases when we in
a loop (m_bb non-NULL) emit a nested cast with too few limbs and
then just use constant indexes for all accesses - in that case
only m_data[save_data_cnt + 1] is initialized and m_data[save_data_cnt]
is NULL.  In those cases, we want to use the former.

2023-12-22  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/113102
	* gimple-lower-bitint.cc (bitint_large_huge::handle_cast): Only
	use m_data[save_data_cnt] if it is non-NULL.

	* gcc.dg/bitint-58.c: New test.

diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc
index 045836ece22fa43a6d5e1eb5dbab60e78d2ae533..880938999f4b1af107d82dc8af0c3038243b89af 100644 (file)
--- a/gcc/gimple-lower-bitint.cc
+++ b/gcc/gimple-lower-bitint.cc
@@ -1491,7 +1491,7 @@ bitint_large_huge::handle_cast (tree lhs_type, tree rhs1, tree idx)
                m_data_cnt = tree_to_uhwi (m_data[save_data_cnt + 2]);
              if (TYPE_UNSIGNED (rhs_type))
                t = build_zero_cst (m_limb_type);
-             else if (m_bb)
+             else if (m_bb && m_data[save_data_cnt])
                t = m_data[save_data_cnt];
              else
                t = m_data[save_data_cnt + 1];

diff --git a/gcc/testsuite/gcc.dg/bitint-58.c b/gcc/testsuite/gcc.dg/bitint-58.c
new file mode 100644 (file)
index 0000000..4368788
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/bitint-58.c
@@ -0,0 +1,31 @@
+/* PR tree-optimization/113102 */
+/* { dg-do compile { target bitint } } */
+/* { dg-options "-std=c23 -O2" } */
+
+_BitInt(3) a;
+#if __BITINT_MAXWIDTH__ >= 4097
+_BitInt(8) b;
+_BitInt(495) c;
+_BitInt(513) d;
+_BitInt(1085) e;
+_BitInt(4096) f;
+
+void
+foo (void)
+{
+  a -= (_BitInt(4097)) d >> b;
+}
+
+void
+bar (void)
+{
+  __builtin_sub_overflow ((_BitInt(767)) c >> e, 0, &a);
+}
+
+void
+baz (void)
+{
+  _BitInt(768) x = (_BitInt(257))f;
+  b /= x >> 0 / 0;     /* { dg-warning "division by zero" } */
+}
+#endif