[gcc r13-4739] loop-invariant: Split preheader edge if the preheader bb ends with jump [PR106751]

[gcc r13-4739] loop-invariant: Split preheader edge if the preheader bb ends with jump [PR106751]

[Jakub Jelinek]

https://gcc.gnu.org/g:ddcaa60983b50378bde1b7e327086fe0ce101795

commit r13-4739-gddcaa60983b50378bde1b7e327086fe0ce101795
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Dec 16 10:19:22 2022 +0100

    loop-invariant: Split preheader edge if the preheader bb ends with jump [PR106751]
    
    The RTL loop passes only request simple preheaders, but don't require
    fallthru preheaders, while move_invariant_reg apparently assumes the
    latter, that it can just append instruction(s) to the end of the preheader
    basic block.
    
    The following patch fixes that by splitting the preheader edge if
    the preheader bb ends with a JUMP_INSN (asm goto in this case).
    Without that we get control flow in the middle of a bb.
    
    2022-12-16  Jakub Jelinek  <jakub@redhat.com>
    
            PR rtl-optimization/106751
            * loop-invariant.cc (move_invariant_reg): If preheader bb ends
            with a JUMP_INSN, split the preheader edge and emit invariants
            into the new preheader basic block.
    
            * gcc.c-torture/compile/pr106751.c: New test.

Diff:
---
 gcc/loop-invariant.cc                          |  2 ++
 gcc/testsuite/gcc.c-torture/compile/pr106751.c | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/gcc/loop-invariant.cc b/gcc/loop-invariant.cc
index f3248540fb1..9b5f6cd3223 100644
--- a/gcc/loop-invariant.cc
+++ b/gcc/loop-invariant.cc
@@ -1837,6 +1837,8 @@ move_invariant_reg (class loop *loop, unsigned invno)
       else if (dump_file)
 	fprintf (dump_file, "Invariant %d moved without introducing a new "
 			    "temporary register\n", invno);
+      if (JUMP_P (BB_END (preheader)))
+	preheader = split_edge (loop_preheader_edge (loop));
       reorder_insns (inv->insn, inv->insn, BB_END (preheader));
       df_recompute_luids (preheader);
 
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr106751.c b/gcc/testsuite/gcc.c-torture/compile/pr106751.c
new file mode 100644
index 00000000000..5fbf93bd332
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr106751.c
@@ -0,0 +1,17 @@
+/* PR rtl-optimization/106751 */
+
+int *foo (void);
+
+void
+bar (void)
+{
+  asm goto ("" : : : : lab);
+  __builtin_unreachable ();
+lab:
+  while (1)
+    {
+      int o;
+      asm ("" : "=r" (o) : "g" (1));
+      *foo () = o;
+    }
+}