Re: RFA: MN10300: Add support for SETLB and Lcc instructions

[Nick Clifton]

Hi Richard,

Thanks for the review. Attached is a revised patch which addresses the issues that you raised:

+/* A special mode used to distinguish the Lcc branch instruction

+   from the Bcc branch instruction.  */
+CC_MODE (CC_LCC);

Why not just use an unspec on the lcc insn.

I should have done. The CC_LCC mode was a holdover from when I was trying to get the doloop patterns to work. The doloop pattern recognizer does not accept UNSPECs, so I had to use a unique CC mode instead. The revised patch uses an UNSPEC.

+  /* What we're doing here is looking for a conditional branch which
+     branches backwards without crossing any non-debug labels.  I.e.
+     the loop has to enter from the top.  */

Ug.  Surely we can re-use the existing loop detection code to find the
inner-most loops.

Cheers
  Nick

gcc/ChangeLog
2011-03-08  Nick Clifton  <ni...@redhat.com>

        * config/mn10300/mn10300.c: Include cfgloop.h.
        (DUMP): New macro.
        (mn10300_insert_setlb_lcc): New function.  Inserts a SETLB and a
        Lcc or a FLcc insn into the instruction stream.
        (mn10300_block_contains_call): New function.  Returns true if the
        given basic block contains a CALL insn.
        (mn10300_loop_contains_call_insn): New function.  Returns true if
        the given loop contains a CALL insn.
        (mn10300_scan_for_setlb_lcc): New function.  Finds opportunities
        to use the SETLB and Lcc or FLcc insns.
        (mn10300_reorg): Invoke mn10300_scan_for_setlb_lcc.
        (TARGET_FLAGS): Add MASK_ALLOW_SETLB.
        * config/mn10300/mn10300.opt (msetlb): New option.  Used to
        disable the SETLB optimization.
        * config/mn10300/mn10300.h (TARGET_CPU_CPP_BUILTINS): Add
        __SETLB__ or __NO_SETLB__.
        * config/mn10300/mn10300.md (UNSPEC_SETLB): New constant.
        (cmpsi): Make visible.
        (setlb): New pattern.
        (Lcc): New pattern.
        (FLcc): New pattern.
        * doc/invoke.texi: Document -mno-setlb option.

We can, but it is a lot more complicated than just performing a simple scan. Still I have tried my best to follow up on this. One thing that does worry me however is that I encountered a segmentation fault whilst trying to free the loop data. (See a comment in the patch for more details). I tried to follow the example of other passes that use the loop information, but I must have gotten something wrong. Any pointers on how to fix this are greatly appreciated.

mn10300.setlb.patch.3
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