This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
RFC: Jump to const_int
- To: gcc at gcc dot gnu dot org, gcc-bugs at gcc dot gnu dot org
- Subject: RFC: Jump to const_int
- From: "John David Anglin" <dave at hiauly1 dot hia dot nrc dot ca>
- Date: Fri, 12 Jan 2001 13:43:22 -0500 (EST)
Flow aborts in make_edges if it finds a plain or unconditional jump that
isn't to a label:
/* Otherwise, we have a plain conditional or unconditional jump. */
else
{
if (! JUMP_LABEL (insn))
abort ();
make_label_edge (edge_cache, bb, JUMP_LABEL (insn), 0);
}
In reviewing the testsuite failures on the vax reported here
<http://gcc.gnu.org/ml/gcc-testresults/2001-01/msg00080.html>,
I found the following testcase fails (991213-3.c) with the above abort:
int jump () { goto * (int (*) ()) 0xbabebec0; }
The rtl generated for jump () is:
;; Function jump
(note 2 0 3 NOTE_INSN_DELETED -1347440721)
(note 3 2 8 NOTE_INSN_FUNCTION_BEG -1347440721)
(jump_insn 8 3 9 (set (pc)
(const_int -1161904448 [0xbabebec0])) -1 (nil)
(nil))
(barrier 9 8 0)
This is not a computed jump because jmp_uses_reg_or_mem only accepts a
REG or MEM that is not in the constant pool.
Changing the predicate for the indirect_jump insn to register_operand
might hide the problem. I think that this would make the jump look like
a computed jump. However, this doesn't seem like the correct solution
since the above jump is effectively an exit.
Should make_edges be changed to recognize a jump to CONST_INT or are
there problems in doing this?
Dave
--
J. David Anglin dave.anglin@nrc.ca
National Research Council of Canada (613) 990-0752 (FAX: 952-6605)