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Subject: [Bug bootstrap/46856] [4.6 regression] internal compiler error in final_scan_insn breaks m68k-linux bootstrap
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46856

--- Comment #4 from Mikael Pettersson <mikpe at it dot uu.se> 2010-12-11 12:17:46 UTC ---
Jakub's r166371 is innocent, all it did was to revert an expansion mode change
in r162618 (2nd PR44790 patch).  Trunk actually started to ICE for this test
case on m68k in r162270:

Author: bernds
Date: Fri Jul 16 23:47:46 2010
New Revision: 162270

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=162270
Log:
    PR target/42235
    * postreload.c (reload_cse_move2add): Return bool, true if anything.
    changed.  All callers changed.
    (move2add_use_add2_insn): Likewise.
    (move2add_use_add3_insn): Likewise.
    (reload_cse_regs): If reload_cse_move2add changed anything, rerun
    reload_combine.
    (RELOAD_COMBINE_MAX_USES): Bump to 16.
    (last_jump_ruid): New static variable.
    (struct reg_use): New members CONTAINING_MEM and RUID.
    (reg_state): New members ALL_OFFSETS_MATCH and REAL_STORE_RUID.
    (reload_combine_split_one_ruid, reload_combine_split_ruids,
    reload_combine_purge_insn_uses, reload_combine_closest_single_use
    reload_combine_purge_reg_uses_after_ruid,
    reload_combine_recognize_const_pattern): New static functions.
    (reload_combine_recognize_pattern): Verify that ALL_OFFSETS_MATCH
    is true for our reg and that we have available index regs.
    (reload_combine_note_use): New args RUID and CONTAINING_MEM.  All
    callers changed.  Use them to initialize fields in struct reg_use.
    (reload_combine): Initialize last_jump_ruid.  Be careful when to
    take PREV_INSN of the scanned insn.  Update REAL_STORE_RUID fields.
    Call reload_combine_recognize_const_pattern.
    (reload_combine_note_store): Update REAL_STORE_RUID field.

which supports Jakub's statement that reload_combine_recognize_const_pattern
misbehaves.