[PATCH] bitint: Handle m_bitfld_load cast in outer m_cast_conditional [PR114555]

[Jakub Jelinek]

Hi!

We ICE on the following testcase, because we use result of a PHI node
which is only conditional because of a m_cast_conditional on the outermost
loops PHI node argument and so is invalid SSA form.

The following patch fixes it like similar cases elsewhere by adding
needed intervening PHI(s).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2024-04-04  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/114555
        * gimple-lower-bitint.cc (bitint_large_huge::handle_cast): For
        m_bitfld_load and save_cast_conditional add any needed PHIs
        and adjust t4 accordingly.

        * gcc.dg/bitint-103.c: New test.
        * gcc.dg/bitint-104.c: New test.

--- gcc/gimple-lower-bitint.cc.jj       2024-03-23 11:19:53.000000000 +0100
+++ gcc/gimple-lower-bitint.cc  2024-04-03 15:31:19.686583203 +0200
@@ -1506,7 +1506,7 @@ bitint_large_huge::handle_cast (tree lhs
          if (m_bitfld_load)
            {
              tree t4;
-             if (!save_first)
+             if (!save_first && !save_cast_conditional)
                t4 = m_data[m_bitfld_load + 1];
              else
                t4 = make_ssa_name (m_limb_type);
@@ -1519,6 +1519,24 @@ bitint_large_huge::handle_cast (tree lhs
              if (edge_true_true)
                add_phi_arg (phi, m_data[m_bitfld_load], edge_true_true,
                             UNKNOWN_LOCATION);
+             if (save_cast_conditional)
+               for (basic_block bb = gsi_bb (m_gsi);;)
+                 {
+                   edge e1 = single_succ_edge (bb);
+                   edge e2 = find_edge (e1->dest, m_bb), e3;
+                   tree t5 = ((e2 && !save_first) ? m_data[m_bitfld_load + 1]
+                              : make_ssa_name (m_limb_type));
+                   phi = create_phi_node (t5, e1->dest);
+                   edge_iterator ei;
+                   FOR_EACH_EDGE (e3, ei, e1->dest->preds)
+                     add_phi_arg (phi, (e3 == e1 ? t4
+                                        : build_zero_cst (m_limb_type)),
+                                  e3, UNKNOWN_LOCATION);
+                   t4 = t5;
+                   if (e2)
+                     break;
+                   bb = e1->dest;
+                 }
              m_data[m_bitfld_load] = t4;
              m_data[m_bitfld_load + 2] = t4;
              m_bitfld_load = 0;
--- gcc/testsuite/gcc.dg/bitint-103.c.jj        2024-04-03 15:34:19.468113199 
+0200
+++ gcc/testsuite/gcc.dg/bitint-103.c   2024-04-03 15:34:05.805300917 +0200
@@ -0,0 +1,16 @@
+/* PR tree-optimization/114555 */
+/* { dg-do compile { target bitint } } */
+/* { dg-options "-std=c23 -O2" } */
+
+#if __BITINT_MAXWIDTH__ >= 1225
+struct S { _BitInt(512) : 98; _BitInt(1225) b : 509; } s;
+_BitInt(1225) a;
+#endif
+
+void
+foo (void)
+{
+#if __BITINT_MAXWIDTH__ >= 1225
+  a ^= (unsigned _BitInt(1025)) s.b;
+#endif
+}
--- gcc/testsuite/gcc.dg/bitint-104.c.jj        2024-04-03 15:36:59.385916107 
+0200
+++ gcc/testsuite/gcc.dg/bitint-104.c   2024-04-03 15:36:28.034346850 +0200
@@ -0,0 +1,17 @@
+/* PR tree-optimization/114555 */
+/* { dg-do compile { target bitint } } */
+/* { dg-options "-std=c23 -O -fno-tree-forwprop" } */
+
+#if __BITINT_MAXWIDTH__ >= 4139
+struct S { _BitInt(31) : 6; _BitInt(513) b : 241; } s;
+_BitInt(4139) a;
+#endif
+
+void
+foo (void)
+{
+#if __BITINT_MAXWIDTH__ >= 4139
+  int i = 0;
+  a -= s.b << i;
+#endif
+}

        Jakub