-/* Determine if the pattern generated by add_optab has a clobber,
- such as might be issued for a flags hard register. To make the
- code elsewhere simpler, we handle cc0 in this same framework.
-
- Return the register if one was discovered. Return NULL_RTX if
- if no flags were found. Return pc_rtx if we got confused. */
-
-static rtx
-discover_flags_reg (void)
-{
- rtx tmp;
- tmp = gen_rtx_REG (word_mode, 10000);
- tmp = gen_add3_insn (tmp, tmp, const2_rtx);
-
- /* If we get something that isn't a simple set, or a
- [(set ..) (clobber ..)], this whole function will go wrong. */
- if (GET_CODE (tmp) == SET)
- return NULL_RTX;
- else if (GET_CODE (tmp) == PARALLEL)
- {
- int found;
-
- if (XVECLEN (tmp, 0) != 2)
- return pc_rtx;
- tmp = XVECEXP (tmp, 0, 1);
- if (GET_CODE (tmp) != CLOBBER)
- return pc_rtx;
- tmp = XEXP (tmp, 0);
-
- /* Don't do anything foolish if the md wanted to clobber a
- scratch or something. We only care about hard regs.
- Moreover we don't like the notion of subregs of hard regs. */
- if (GET_CODE (tmp) == SUBREG
- && REG_P (SUBREG_REG (tmp))
- && REGNO (SUBREG_REG (tmp)) < FIRST_PSEUDO_REGISTER)
- return pc_rtx;
- found = (REG_P (tmp) && REGNO (tmp) < FIRST_PSEUDO_REGISTER);
-
- return (found ? tmp : NULL_RTX);
- }
-
- return pc_rtx;
-}
-
-/* It is a tedious task identifying when the flags register is live and
- when it is safe to optimize. Since we process the instruction stream
- multiple times, locate and record these live zones by marking the
- mode of the instructions --
-
- QImode is used on the instruction at which the flags becomes live.
-
- HImode is used within the range (exclusive) that the flags are
- live. Thus the user of the flags is not marked.
-
- All other instructions are cleared to VOIDmode. */
-
-/* Used to communicate with flags_set_1. */
-static rtx flags_set_1_rtx;
-static int flags_set_1_set;
-
-static void
-mark_flags_life_zones (rtx flags)
-{
- int flags_regno;
- int flags_nregs;
- basic_block block;
-
-#ifdef HAVE_cc0
- /* If we found a flags register on a cc0 host, bail. */
- if (flags == NULL_RTX)
- flags = cc0_rtx;
- else if (flags != cc0_rtx)
- flags = pc_rtx;
-#endif
-
- /* Simple cases first: if no flags, clear all modes. If confusing,
- mark the entire function as being in a flags shadow. */
- if (flags == NULL_RTX || flags == pc_rtx)
- {
- enum machine_mode mode = (flags ? HImode : VOIDmode);
- rtx insn;
- for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
- PUT_MODE (insn, mode);
- return;
- }
-
-#ifdef HAVE_cc0
- flags_regno = -1;
- flags_nregs = 1;
-#else
- flags_regno = REGNO (flags);
- flags_nregs = hard_regno_nregs[flags_regno][GET_MODE (flags)];
-#endif
- flags_set_1_rtx = flags;
-
- /* Process each basic block. */
- FOR_EACH_BB_REVERSE (block)
- {
- rtx insn, end;
- int live;
-
- insn = BB_HEAD (block);
- end = BB_END (block);
-
- /* Look out for the (unlikely) case of flags being live across
- basic block boundaries. */
- live = 0;
-#ifndef HAVE_cc0
- {
- int i;
- for (i = 0; i < flags_nregs; ++i)
- live |= REGNO_REG_SET_P (df_get_live_in (block), flags_regno + i);
- }
-#endif
-
- while (1)
- {
- /* Process liveness in reverse order of importance --
- alive, death, birth. This lets more important info
- overwrite the mode of lesser info. */
-
- if (INSN_P (insn))
- {
-#ifdef HAVE_cc0
- /* In the cc0 case, death is not marked in reg notes,
- but is instead the mere use of cc0 when it is alive. */
- if (live && reg_mentioned_p (cc0_rtx, PATTERN (insn)))
- live = 0;
-#else
- /* In the hard reg case, we watch death notes. */
- if (live && find_regno_note (insn, REG_DEAD, flags_regno))
- live = 0;
-#endif
- PUT_MODE (insn, (live ? HImode : VOIDmode));
-
- /* In either case, birth is denoted simply by its presence
- as the destination of a set. */
- flags_set_1_set = 0;
- note_stores (PATTERN (insn), flags_set_1, NULL);
- if (flags_set_1_set)
- {
- live = 1;
- PUT_MODE (insn, QImode);
- }
- }
- else
- PUT_MODE (insn, (live ? HImode : VOIDmode));
-
- if (insn == end)
- break;
- insn = NEXT_INSN (insn);
- }
- }
-}
-
-/* A subroutine of mark_flags_life_zones, called through note_stores. */
-
-static void
-flags_set_1 (rtx x, const_rtx pat, void *data ATTRIBUTE_UNUSED)
-{
- if (GET_CODE (pat) == SET
- && reg_overlap_mentioned_p (x, flags_set_1_rtx))
- flags_set_1_set = 1;
-}
-