[Bug rtl-optimization/60651] Mode switching instructions are sometimes emitted in the wrong order

["amylaar at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60651

--- Comment #2 from Jorn Wolfgang Rennecke <amylaar at gcc dot gnu.org> ---
Created attachment 32526
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32526&action=edit
preprocessed libjava file

With the latest proposed patch, we get an assertion failure building libjava
during the i686-pc-linux-gnu bootstrap; this is the command line:

./cc1plus -fpreprocessed interpret.ii -quiet -dumpbase interpret.cc
-mtune=generic -march=pentiumpro -auxbase-strip .libs/interpret.o -g -O2
-Wswitch-enum -Wextra -Wall -version -fno-rtti -fnon-call-exceptions
-fdollars-in-identifiers -ffloat-store -fomit-frame-pointer -fwrapv -fPIC -o
interpret.s

The block in question looks like this:

(code_label/s 9087 9590 9090 17 990 "" [1 uses])

(note 9090 9087 9088 17 [bb 17] NOTE_INSN_BASIC_BLOCK)

where the BB_HEAD is the CODE_LABEL, and the BB_END is the
NOTE_INSN_BASIC_BLOCK.

The caller of new_seginfo is the abnormal-edge code that I've patched to
handle non-empty blocks differently; this block is mistaken for a non-empty
block.

Now, interestingly, the pre-existing code already handles this incorrectly,
by inserting instructions between the CODE_LABEL an the NOTE_INSN_BASIC_BLOCK.