bitint: Fix bitfield loads in handle_cast [PR114433]

We ICE on the following testcase, because handle_cast was incorrectly
testing !m_first to see whether it should use m_data[m_bitfld_load + 1]
or fresh SSA_NAME for a PHI result.
Now, m_first is in the routine sometimes temporarily cleared in between
doing prepare_data_in_out and the !m_first check and only before returning
restored from the save_first copy.
Without this patch, we try to use the same SSA_NAME (_12 here) in 2
different PHI results which is obviously invalid IL and ICEs very quickly.

2024-03-23  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/114433
	* gimple-lower-bitint.cc (bitint_large_huge::handle_cast): For
	m_bitfld_load check save_first rather than m_first.

	* gcc.dg/torture/bitint-68.c: New test.

diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc
index 6f13c657c6b825f8e0532cb3a8016802759244c2..40a1084afb3bb824a90c77dac9cfe0019baed967 100644 (file)
--- a/gcc/gimple-lower-bitint.cc
+++ b/gcc/gimple-lower-bitint.cc
@@ -1506,7 +1506,7 @@ bitint_large_huge::handle_cast (tree lhs_type, tree rhs1, tree idx)
          if (m_bitfld_load)
            {
              tree t4;
-             if (!m_first)
+             if (!save_first)
                t4 = m_data[m_bitfld_load + 1];
              else
                t4 = make_ssa_name (m_limb_type);

diff --git a/gcc/testsuite/gcc.dg/torture/bitint-68.c b/gcc/testsuite/gcc.dg/torture/bitint-68.c
new file mode 100644 (file)
index 0000000..8320e8e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/bitint-68.c
@@ -0,0 +1,28 @@
+/* PR tree-optimization/114433 */
+/* { dg-do run { target bitint } } */
+/* { dg-options "-std=c23" } */
+/* { dg-skip-if "" { ! run_expensive_tests }  { "*" } { "-O0" "-O2" } } */
+/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
+
+#if __BITINT_MAXWIDTH__ >= 511
+struct S { int : 31; _BitInt(511) b : 300; } s;
+
+__attribute__((noipa)) _BitInt(511)
+foo (void) 
+{
+  return s.b << 1;
+}
+#endif
+
+int
+main ()
+{
+#if __BITINT_MAXWIDTH__ >= 511
+  s.b = 642460398785925402356009598661384732715767737595497615767135001949421105426024498988100867wb;
+  if (foo () != ((_BitInt(511)) 642460398785925402356009598661384732715767737595497615767135001949421105426024498988100867wb) << 1)
+    __builtin_abort ();
+  s.b = 2655156766298562299560755420298083843774074962786295887660222690220887wb;
+  if (foo () != ((_BitInt(511)) 2655156766298562299560755420298083843774074962786295887660222690220887wb) << 1)
+    __builtin_abort ();
+#endif
+}