/* Perform doloop optimizations Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc. Contributed by Michael P. Hayes (m.hayes@elec.canterbury.ac.nz) This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "rtl.h" #include "flags.h" #include "expr.h" #include "loop.h" #include "hard-reg-set.h" #include "basic-block.h" #include "toplev.h" #include "tm_p.h" #include "cfgloop.h" /* This module is used to modify loops with a determinable number of iterations to use special low-overhead looping instructions. It first validates whether the loop is well behaved and has a determinable number of iterations (either at compile or run-time). It then modifies the loop to use a low-overhead looping pattern as follows: 1. A pseudo register is allocated as the loop iteration counter. 2. The number of loop iterations is calculated and is stored in the loop counter. 3. At the end of the loop, the jump insn is replaced by the doloop_end pattern. The compare must remain because it might be used elsewhere. If the loop-variable or condition register are used elsewhere, they will be eliminated by flow. 4. An optional doloop_begin pattern is inserted at the top of the loop. */ #ifdef HAVE_doloop_end static unsigned HOST_WIDE_INT doloop_iterations_max (const struct loop_info *, enum machine_mode, int); static int doloop_valid_p (const struct loop *, rtx); static int doloop_modify (const struct loop *, rtx, rtx, rtx, rtx, rtx); static int doloop_modify_runtime (const struct loop *, rtx, rtx, rtx, enum machine_mode, rtx); /* Return the loop termination condition for PATTERN or zero if it is not a decrement and branch jump insn. */ rtx doloop_condition_get (rtx pattern) { rtx cmp; rtx inc; rtx reg; rtx condition; /* The canonical doloop pattern we expect is: (parallel [(set (pc) (if_then_else (condition) (label_ref (label)) (pc))) (set (reg) (plus (reg) (const_int -1))) (additional clobbers and uses)]) Some machines (IA-64) make the decrement conditional on the condition as well, so we don't bother verifying the actual decrement. In summary, the branch must be the first entry of the parallel (also required by jump.c), and the second entry of the parallel must be a set of the loop counter register. */ if (GET_CODE (pattern) != PARALLEL) return 0; cmp = XVECEXP (pattern, 0, 0); inc = XVECEXP (pattern, 0, 1); /* Check for (set (reg) (something)). */ if (GET_CODE (inc) != SET || ! REG_P (SET_DEST (inc))) return 0; /* Extract loop counter register. */ reg = SET_DEST (inc); /* Check for (set (pc) (if_then_else (condition) (label_ref (label)) (pc))). */ if (GET_CODE (cmp) != SET || SET_DEST (cmp) != pc_rtx || GET_CODE (SET_SRC (cmp)) != IF_THEN_ELSE || GET_CODE (XEXP (SET_SRC (cmp), 1)) != LABEL_REF || XEXP (SET_SRC (cmp), 2) != pc_rtx) return 0; /* Extract loop termination condition. */ condition = XEXP (SET_SRC (cmp), 0); if ((GET_CODE (condition) != GE && GET_CODE (condition) != NE) || GET_CODE (XEXP (condition, 1)) != CONST_INT) return 0; if (XEXP (condition, 0) == reg) return condition; if (GET_CODE (XEXP (condition, 0)) == PLUS && XEXP (XEXP (condition, 0), 0) == reg) return condition; /* ??? If a machine uses a funny comparison, we could return a canonicalised form here. */ return 0; } /* Return an estimate of the maximum number of loop iterations for the loop specified by LOOP or zero if the loop is not normal. MODE is the mode of the iteration count and NONNEG is nonzero if the iteration count has been proved to be non-negative. */ static unsigned HOST_WIDE_INT doloop_iterations_max (const struct loop_info *loop_info, enum machine_mode mode, int nonneg) { unsigned HOST_WIDE_INT n_iterations_max; enum rtx_code code; rtx min_value; rtx max_value; HOST_WIDE_INT abs_inc; int neg_inc; neg_inc = 0; abs_inc = INTVAL (loop_info->increment); if (abs_inc < 0) { abs_inc = -abs_inc; neg_inc = 1; } if (neg_inc) { code = swap_condition (loop_info->comparison_code); min_value = loop_info->final_equiv_value; max_value = loop_info->initial_equiv_value; } else { code = loop_info->comparison_code; min_value = loop_info->initial_equiv_value; max_value = loop_info->final_equiv_value; } /* Since the loop has a VTOP, we know that the initial test will be true and thus the value of max_value should be greater than the value of min_value. Thus the difference should always be positive and the code must be LT, LE, LTU, LEU, or NE. Otherwise the loop is not normal, e.g., `for (i = 0; i < 10; i--)'. */ switch (code) { case LTU: case LEU: { unsigned HOST_WIDE_INT umax; unsigned HOST_WIDE_INT umin; if (GET_CODE (min_value) == CONST_INT) umin = INTVAL (min_value); else umin = 0; if (GET_CODE (max_value) == CONST_INT) umax = INTVAL (max_value); else umax = ((unsigned) 2 << (GET_MODE_BITSIZE (mode) - 1)) - 1; n_iterations_max = umax - umin; break; } case LT: case LE: { HOST_WIDE_INT smax; HOST_WIDE_INT smin; if (GET_CODE (min_value) == CONST_INT) smin = INTVAL (min_value); else smin = -((unsigned) 1 << (GET_MODE_BITSIZE (mode) - 1)); if (GET_CODE (max_value) == CONST_INT) smax = INTVAL (max_value); else smax = ((unsigned) 1 << (GET_MODE_BITSIZE (mode) - 1)) - 1; n_iterations_max = smax - smin; break; } case NE: if (GET_CODE (min_value) == CONST_INT && GET_CODE (max_value) == CONST_INT) n_iterations_max = INTVAL (max_value) - INTVAL (min_value); else /* We need to conservatively assume that we might have the maximum number of iterations without any additional knowledge. */ n_iterations_max = ((unsigned) 2 << (GET_MODE_BITSIZE (mode) - 1)) - 1; break; default: return 0; } n_iterations_max /= abs_inc; /* If we know that the iteration count is non-negative then adjust n_iterations_max if it is so large that it appears negative. */ if (nonneg && n_iterations_max > ((unsigned) 1 << (GET_MODE_BITSIZE (mode) - 1))) n_iterations_max = ((unsigned) 1 << (GET_MODE_BITSIZE (mode) - 1)) - 1; return n_iterations_max; } /* Return nonzero if the loop specified by LOOP is suitable for the use of special low-overhead looping instructions. */ static int doloop_valid_p (const struct loop *loop, rtx jump_insn) { const struct loop_info *loop_info = LOOP_INFO (loop); /* The loop must have a conditional jump at the end. */ if (! any_condjump_p (jump_insn) || ! onlyjump_p (jump_insn)) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Invalid jump at loop end.\n"); return 0; } /* Give up if a loop has been completely unrolled. */ if (loop_info->n_iterations == loop_info->unroll_number) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Loop completely unrolled.\n"); return 0; } /* The loop must have a single exit target. A break or return statement within a loop will generate multiple loop exits. Another example of a loop that currently generates multiple exit targets is for (i = 0; i < (foo ? 8 : 4); i++) { }. */ if (loop_info->has_multiple_exit_targets || loop->exit_count) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Loop has multiple exit targets.\n"); return 0; } /* An indirect jump may jump out of the loop. */ if (loop_info->has_indirect_jump) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Indirect jump in function.\n"); return 0; } /* A called function may clobber any special registers required for low-overhead looping. */ if (loop_info->has_call) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Function call in loop.\n"); return 0; } /* Some targets (eg, PPC) use the count register for branch on table instructions. ??? This should be a target specific check. */ if (loop_info->has_tablejump) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Computed branch in the loop.\n"); return 0; } if (! loop_info->increment) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Could not determine iteration info.\n"); return 0; } if (GET_CODE (loop_info->increment) != CONST_INT) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Increment not an integer constant.\n"); return 0; } /* There is no guarantee that a NE loop will terminate if the absolute increment is not unity. ??? We could compute this condition at run-time and have an additional jump around the loop to ensure an infinite loop. */ if (loop_info->comparison_code == NE && !loop_info->preconditioned && INTVAL (loop_info->increment) != -1 && INTVAL (loop_info->increment) != 1) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: NE loop with non-unity increment.\n"); return 0; } /* Check for loops that may not terminate under special conditions. */ if (! loop_info->n_iterations && ((loop_info->comparison_code == LEU && INTVAL (loop_info->increment) > 0) || (loop_info->comparison_code == GEU && INTVAL (loop_info->increment) < 0) || (loop_info->comparison_code == LTU && INTVAL (loop_info->increment) > 1) || (loop_info->comparison_code == GTU && INTVAL (loop_info->increment) < -1))) { /* If the comparison is LEU and the comparison value is UINT_MAX then the loop will not terminate. Similarly, if the comparison code is GEU and the comparison value is 0, the loop will not terminate. If the absolute increment is not 1, the loop can be infinite even with LTU/GTU, e.g. for (i = 3; i > 0; i -= 2) Note that with LE and GE, the loop behavior is undefined (C++ standard section 5 clause 5) if an overflow occurs, say between INT_MAX and INT_MAX + 1. We thus don't have to worry about these two cases. ??? We could compute these conditions at run-time and have a additional jump around the loop to ensure an infinite loop. However, it is very unlikely that this is the intended behavior of the loop and checking for these rare boundary conditions would pessimize all other code. If the loop is executed only a few times an extra check to restart the loop could use up most of the benefits of using a count register loop. Note however, that normally, this restart branch would never execute, so it could be predicted well by the CPU. We should generate the pessimistic code by default, and have an option, e.g. -funsafe-loops that would enable count-register loops in this case. */ if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Possible infinite iteration case ignored.\n"); } return 1; } /* Modify the loop to use the low-overhead looping insn where LOOP describes the loop, ITERATIONS is an RTX containing the desired number of loop iterations, ITERATIONS_MAX is a CONST_INT specifying the maximum number of loop iterations, and DOLOOP_INSN is the low-overhead looping insn to emit at the end of the loop. This returns nonzero if it was successful. */ static int doloop_modify (const struct loop *loop, rtx iterations, rtx iterations_max, rtx doloop_seq, rtx start_label, rtx condition) { rtx counter_reg; rtx count; rtx sequence; rtx jump_insn; int nonneg = 0; int decrement_count; jump_insn = prev_nonnote_insn (loop->end); if (loop_dump_stream) { fprintf (loop_dump_stream, "Doloop: Inserting doloop pattern ("); if (GET_CODE (iterations) == CONST_INT) fprintf (loop_dump_stream, HOST_WIDE_INT_PRINT_DEC, INTVAL (iterations)); else fputs ("runtime", loop_dump_stream); fputs (" iterations).", loop_dump_stream); } /* Emit the label that will delimit the top of the loop. This has to be done before the delete_insn call below, to prevent delete_insn from deleting too much. */ emit_label_after (start_label, loop->top ? loop->top : loop->start); LABEL_NUSES (start_label)++; /* Discard original jump to continue loop. The original compare result may still be live, so it cannot be discarded explicitly. */ delete_related_insns (jump_insn); counter_reg = XEXP (condition, 0); if (GET_CODE (counter_reg) == PLUS) counter_reg = XEXP (counter_reg, 0); start_sequence (); count = iterations; decrement_count = 0; switch (GET_CODE (condition)) { case NE: /* Currently only NE tests against zero and one are supported. */ if (XEXP (condition, 1) == const0_rtx) decrement_count = 1; else if (XEXP (condition, 1) != const1_rtx) abort (); break; case GE: /* Currently only GE tests against zero are supported. */ if (XEXP (condition, 1) != const0_rtx) abort (); /* The iteration count needs decrementing for a GE test. */ decrement_count = 1; /* Determine if the iteration counter will be non-negative. Note that the maximum value loaded is iterations_max - 1. */ if ((unsigned HOST_WIDE_INT) INTVAL (iterations_max) <= ((unsigned) 1 << (GET_MODE_BITSIZE (GET_MODE (counter_reg)) - 1))) nonneg = 1; break; /* Abort if an invalid doloop pattern has been generated. */ default: abort (); } if (decrement_count) { if (GET_CODE (count) == CONST_INT) count = GEN_INT (INTVAL (count) - 1); else count = expand_simple_binop (GET_MODE (counter_reg), MINUS, count, const1_rtx, 0, 0, OPTAB_LIB_WIDEN); } /* Insert initialization of the count register into the loop header. */ convert_move (counter_reg, count, 1); sequence = get_insns (); end_sequence (); emit_insn_before (sequence, loop->start); /* Some targets (eg, C4x) need to initialize special looping registers. */ #ifdef HAVE_doloop_begin { rtx init; init = gen_doloop_begin (counter_reg, GET_CODE (iterations) == CONST_INT ? iterations : const0_rtx, iterations_max, GEN_INT (loop->level)); if (init) { start_sequence (); emit_insn (init); sequence = get_insns (); end_sequence (); emit_insn_after (sequence, loop->start); } } #endif /* Insert the new low-overhead looping insn. */ emit_jump_insn_before (doloop_seq, loop->end); jump_insn = prev_nonnote_insn (loop->end); JUMP_LABEL (jump_insn) = start_label; /* Add a REG_NONNEG note if the actual or estimated maximum number of iterations is non-negative. */ if (nonneg) { REG_NOTES (jump_insn) = gen_rtx_EXPR_LIST (REG_NONNEG, NULL_RTX, REG_NOTES (jump_insn)); } return 1; } /* Handle the more complex case, where the bounds are not known at compile time. In this case we generate a run_time calculation of the number of iterations. We rely on the existence of a run-time guard to ensure that the loop executes at least once, i.e., initial_value obeys the loop comparison condition. If a guard is not present, we emit one. The loop to modify is described by LOOP. ITERATIONS_MAX is a CONST_INT specifying the estimated maximum number of loop iterations. DOLOOP_INSN is the low-overhead looping insn to insert. Returns nonzero if loop successfully modified. */ static int doloop_modify_runtime (const struct loop *loop, rtx iterations_max, rtx doloop_seq, rtx start_label, enum machine_mode mode, rtx condition) { const struct loop_info *loop_info = LOOP_INFO (loop); HOST_WIDE_INT abs_inc; HOST_WIDE_INT abs_loop_inc; int neg_inc; rtx diff; rtx sequence; rtx iterations; rtx initial_value; rtx final_value; rtx increment; int unsigned_p; enum rtx_code comparison_code; increment = loop_info->increment; initial_value = loop_info->initial_value; final_value = loop_info->final_value; neg_inc = 0; abs_inc = INTVAL (increment); if (abs_inc < 0) { abs_inc = -abs_inc; neg_inc = 1; } comparison_code = loop_info->comparison_code; unsigned_p = (comparison_code == LTU || comparison_code == LEU || comparison_code == GTU || comparison_code == GEU || comparison_code == NE); /* The number of iterations (prior to any loop unrolling) is given by: n = (abs (final - initial) + abs_inc - 1) / abs_inc. However, it is possible for the summation to overflow, and a safer method is: n = abs (final - initial) / abs_inc; n += (abs (final - initial) % abs_inc) != 0; But when abs_inc is a power of two, the summation won't overflow except in cases where the loop never terminates. So we don't need to use this more costly calculation. If the loop has been unrolled, the full calculation is t1 = abs_inc * unroll_number; increment per loop n = (abs (final - initial) + abs_inc - 1) / t1; full loops n += (abs (final - initial) + abs_inc - 1) % t1) >= abs_inc; partial loop which works out to be equivalent to n = (abs (final - initial) + t1 - 1) / t1; In the case where the loop was preconditioned, a few iterations may have been executed earlier; but 'initial' was adjusted as they were executed, so we don't need anything special for that case here. As above, when t1 is a power of two we don't need to worry about overflow. The division and modulo operations can be avoided by requiring that the increment is a power of 2 (precondition_loop_p enforces this requirement). Nevertheless, the RTX_COSTS should be checked to see if a fast divmod is available. */ start_sequence (); /* abs (final - initial) */ diff = expand_simple_binop (mode, MINUS, copy_rtx (neg_inc ? initial_value : final_value), copy_rtx (neg_inc ? final_value : initial_value), NULL_RTX, unsigned_p, OPTAB_LIB_WIDEN); /* Some code transformations can result in code akin to tmp = i + 1; ... goto scan_start; top: tmp = tmp + 1; scan_start: i = tmp; if (i < n) goto top; We'll have already detected this form of loop in scan_loop, and set loop->top and loop->scan_start appropriately. In this situation, we skip the increment the first time through the loop, which results in an incorrect estimate of the number of iterations. Adjust the difference to compensate. */ /* ??? Logically, it would seem this belongs in loop_iterations. However, this causes regressions e.g. on x86 execute/20011008-3.c, so I do not believe we've properly characterized the exact nature of the problem. In the meantime, this fixes execute/20011126-2.c on ia64 and some Ada front end miscompilation on ppc. */ if (loop->scan_start) { rtx iteration_var = loop_info->iteration_var; struct loop_ivs *ivs = LOOP_IVS (loop); struct iv_class *bl; if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == BASIC_INDUCT) bl = REG_IV_CLASS (ivs, REGNO (iteration_var)); else if (REG_IV_TYPE (ivs, REGNO (iteration_var)) == GENERAL_INDUCT) { struct induction *v = REG_IV_INFO (ivs, REGNO (iteration_var)); bl = REG_IV_CLASS (ivs, REGNO (v->src_reg)); } else /* Iteration var must be an induction variable to get here. */ abort (); if (INSN_UID (bl->biv->insn) < max_uid_for_loop && INSN_LUID (bl->biv->insn) < INSN_LUID (loop->scan_start)) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Basic induction var skips initial incr.\n"); diff = expand_simple_binop (mode, PLUS, diff, GEN_INT (abs_inc), diff, unsigned_p, OPTAB_LIB_WIDEN); } } abs_loop_inc = abs_inc * loop_info->unroll_number; if (abs_loop_inc != 1) { int shift_count; shift_count = exact_log2 (abs_loop_inc); if (shift_count < 0) abort (); /* (abs (final - initial) + abs_inc * unroll_number - 1) */ diff = expand_simple_binop (GET_MODE (diff), PLUS, diff, GEN_INT (abs_loop_inc - 1), diff, 1, OPTAB_LIB_WIDEN); /* (abs (final - initial) + abs_inc * unroll_number - 1) / (abs_inc * unroll_number) */ diff = expand_simple_binop (GET_MODE (diff), LSHIFTRT, diff, GEN_INT (shift_count), diff, 1, OPTAB_LIB_WIDEN); } iterations = diff; /* If there is a NOTE_INSN_LOOP_VTOP, we have a `for' or `while' style loop, with a loop exit test at the start. Thus, we can assume that the loop condition was true when the loop was entered. `do-while' loops require special treatment since the exit test is not executed before the start of the loop. We need to determine if the loop will terminate after the first pass and to limit the iteration count to one if necessary. */ if (! loop->vtop) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Do-while loop.\n"); /* A `do-while' loop must iterate at least once. For code like i = initial; do { ... } while (++i < final); we will calculate a bogus iteration count if initial > final. So detect this and set the iteration count to 1. Note that if the loop has been unrolled, then the loop body is guaranteed to execute at least once. Also, when the comparison is NE, our calculated count will be OK. */ if (loop_info->unroll_number == 1 && comparison_code != NE) { rtx label; /* Emit insns to test if the loop will immediately terminate and to set the iteration count to 1 if true. */ label = gen_label_rtx(); emit_cmp_and_jump_insns (copy_rtx (initial_value), copy_rtx (loop_info->comparison_value), comparison_code, NULL_RTX, mode, 0, label); JUMP_LABEL (get_last_insn ()) = label; LABEL_NUSES (label)++; emit_move_insn (iterations, const1_rtx); emit_label (label); } } sequence = get_insns (); end_sequence (); emit_insn_before (sequence, loop->start); return doloop_modify (loop, iterations, iterations_max, doloop_seq, start_label, condition); } /* This is the main entry point. Process loop described by LOOP validating that the loop is suitable for conversion to use a low overhead looping instruction, replacing the jump insn where suitable. We distinguish between loops with compile-time bounds and those with run-time bounds. Information from LOOP is used to compute the number of iterations and to determine whether the loop is a candidate for this optimization. Returns nonzero if loop successfully modified. */ int doloop_optimize (const struct loop *loop) { struct loop_info *loop_info = LOOP_INFO (loop); rtx initial_value; rtx final_value; rtx increment; rtx jump_insn; enum machine_mode mode; unsigned HOST_WIDE_INT n_iterations; unsigned HOST_WIDE_INT n_iterations_max; rtx doloop_seq, doloop_pat, doloop_reg; rtx iterations; rtx iterations_max; rtx start_label; rtx condition; if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Processing loop %d, enclosed levels %d.\n", loop->num, loop->level); jump_insn = prev_nonnote_insn (loop->end); /* Check that loop is a candidate for a low-overhead looping insn. */ if (! doloop_valid_p (loop, jump_insn)) return 0; /* Determine if the loop can be safely, and profitably, preconditioned. While we don't precondition the loop in a loop unrolling sense, this test ensures that the loop is well behaved and that the increment is a constant integer. */ if (! precondition_loop_p (loop, &initial_value, &final_value, &increment, &mode)) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Cannot precondition loop.\n"); return 0; } /* Determine or estimate the maximum number of loop iterations. */ n_iterations = loop_info->n_iterations; if (n_iterations) { /* This is the simple case where the initial and final loop values are constants. */ n_iterations_max = n_iterations; } else { int nonneg = find_reg_note (jump_insn, REG_NONNEG, 0) != 0; /* This is the harder case where the initial and final loop values may not be constants. */ n_iterations_max = doloop_iterations_max (loop_info, mode, nonneg); if (! n_iterations_max) { /* We have something like `for (i = 0; i < 10; i--)'. */ if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Not normal loop.\n"); return 0; } } /* Account for loop unrolling in the iteration count. This will have no effect if loop_iterations could not determine the number of iterations. */ n_iterations /= loop_info->unroll_number; n_iterations_max /= loop_info->unroll_number; if (n_iterations && n_iterations < 3) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Too few iterations (%ld) to be profitable.\n", (long int) n_iterations); return 0; } iterations = GEN_INT (n_iterations); iterations_max = GEN_INT (n_iterations_max); /* Generate looping insn. If the pattern FAILs then give up trying to modify the loop since there is some aspect the back-end does not like. */ start_label = gen_label_rtx (); doloop_reg = gen_reg_rtx (mode); doloop_seq = gen_doloop_end (doloop_reg, iterations, iterations_max, GEN_INT (loop->level), start_label); if (! doloop_seq && mode != word_mode) { PUT_MODE (doloop_reg, word_mode); doloop_seq = gen_doloop_end (doloop_reg, iterations, iterations_max, GEN_INT (loop->level), start_label); } if (! doloop_seq) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Target unwilling to use doloop pattern!\n"); return 0; } /* If multiple instructions were created, the last must be the jump instruction. Also, a raw define_insn may yield a plain pattern. */ doloop_pat = doloop_seq; if (INSN_P (doloop_pat)) { while (NEXT_INSN (doloop_pat) != NULL_RTX) doloop_pat = NEXT_INSN (doloop_pat); if (GET_CODE (doloop_pat) == JUMP_INSN) doloop_pat = PATTERN (doloop_pat); else doloop_pat = NULL_RTX; } if (! doloop_pat || ! (condition = doloop_condition_get (doloop_pat))) { if (loop_dump_stream) fprintf (loop_dump_stream, "Doloop: Unrecognizable doloop pattern!\n"); return 0; } if (n_iterations != 0) /* Handle the simpler case, where we know the iteration count at compile time. */ return doloop_modify (loop, iterations, iterations_max, doloop_seq, start_label, condition); else /* Handle the harder case, where we must add additional runtime tests. */ return doloop_modify_runtime (loop, iterations_max, doloop_seq, start_label, mode, condition); } #endif /* HAVE_doloop_end */