Handle epilogues that contain jumps

The prologue/epilogue pass allows the prologue sequence to contain
jumps.  The sequence is then partitioned into basic blocks using
find_many_sub_basic_blocks.

This patch treats epilogues in a similar way.  Since only one block
might need to be split, the patch (re)introduces a find_sub_basic_blocks
routine to handle a single block.

The new routine hard-codes the assumption that split_block will chain
the new block immediately after the original block.  The routine doesn't
try to replicate the fix for PR81030, since that was specific to
gimple->rtl expansion.

The patch is needed for follow-on aarch64 patches that add conditional
code to the epilogue.  The tests are part of those patches.

gcc/
	* cfgbuild.h (find_sub_basic_blocks): Declare.
	* cfgbuild.cc (update_profile_for_new_sub_basic_block): New function,
	split out from...
	(find_many_sub_basic_blocks): ...here.
	(find_sub_basic_blocks): New function.
	* function.cc (thread_prologue_and_epilogue_insns): Handle
	epilogues that contain jumps.

1 files changed, 4 insertions, 0 deletions

diff --git a/gcc/function.cc b/gcc/function.cc
index 336af28..afb0b33 100644
--- a/gcc/function.cc
+++ b/gcc/function.cc
@@ -6112,6 +6112,8 @@ thread_prologue_and_epilogue_insns (void)
 		  && returnjump_p (BB_END (e->src)))
 		e->flags &= ~EDGE_FALLTHRU;
 	    }
+
+	  find_sub_basic_blocks (BLOCK_FOR_INSN (epilogue_seq));
 	}
       else if (next_active_insn (BB_END (exit_fallthru_edge->src)))
 	{
@@ -6210,6 +6212,8 @@ thread_prologue_and_epilogue_insns (void)
 	  set_insn_locations (seq, epilogue_location);
 
 	  emit_insn_before (seq, insn);
+
+	  find_sub_basic_blocks (BLOCK_FOR_INSN (insn));
 	}
     }