diff options
Diffstat (limited to 'contrib/gcc/doloop.c')
| -rw-r--r-- | contrib/gcc/doloop.c | 69 |
1 files changed, 34 insertions, 35 deletions
diff --git a/contrib/gcc/doloop.c b/contrib/gcc/doloop.c index 25deb503..67b742c 100644 --- a/contrib/gcc/doloop.c +++ b/contrib/gcc/doloop.c @@ -140,7 +140,7 @@ doloop_condition_get (pattern) /* 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 non-zero if + 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 (loop_info, mode, nonneg) @@ -249,7 +249,7 @@ doloop_iterations_max (loop_info, mode, nonneg) } -/* Return non-zero if the loop specified by LOOP is suitable for +/* Return nonzero if the loop specified by LOOP is suitable for the use of special low-overhead looping instructions. */ static int doloop_valid_p (loop, jump_insn) @@ -263,7 +263,7 @@ doloop_valid_p (loop, jump_insn) || ! onlyjump_p (jump_insn)) { if (loop_dump_stream) - fprintf (loop_dump_stream, + fprintf (loop_dump_stream, "Doloop: Invalid jump at loop end.\n"); return 0; } @@ -339,6 +339,7 @@ doloop_valid_p (loop, jump_insn) 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) { @@ -361,13 +362,13 @@ doloop_valid_p (loop, jump_insn) { /* 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 initial value is 0, the loop - will not terminate. + 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 behaviour is undefined + 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. @@ -375,7 +376,7 @@ doloop_valid_p (loop, jump_insn) ??? 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 - behaviour of the loop and checking for these rare boundary + 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 @@ -399,7 +400,7 @@ doloop_valid_p (loop, jump_insn) 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 non-zero if it was successful. */ + returns nonzero if it was successful. */ static int doloop_modify (loop, iterations, iterations_max, doloop_seq, start_label, condition) @@ -490,7 +491,7 @@ doloop_modify (loop, iterations, iterations_max, /* Insert initialization of the count register into the loop header. */ convert_move (counter_reg, count, 1); - sequence = gen_sequence (); + sequence = get_insns (); end_sequence (); emit_insn_before (sequence, loop->start); @@ -508,7 +509,7 @@ doloop_modify (loop, iterations, iterations_max, { start_sequence (); emit_insn (init); - sequence = gen_sequence (); + sequence = get_insns (); end_sequence (); emit_insn_after (sequence, loop->start); } @@ -539,7 +540,7 @@ doloop_modify (loop, iterations, iterations_max, 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 non-zero if loop successfully modified. */ + insn to insert. Returns nonzero if loop successfully modified. */ static int doloop_modify_runtime (loop, iterations_max, doloop_seq, start_label, mode, condition) @@ -600,18 +601,17 @@ doloop_modify_runtime (loop, iterations_max, 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; + 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; - However, in certain cases the unrolled loop will be preconditioned - by emitting copies of the loop body with conditional branches, - so that the unrolled loop is always a full loop and thus needs - no exit tests. In this case we don't want to add the partial - loop count. As above, when t1 is a power of two we don't need to - worry about overflow. + 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 @@ -686,15 +686,13 @@ doloop_modify_runtime (loop, iterations_max, if (shift_count < 0) abort (); - if (loop_info->preconditioned) - diff = expand_simple_binop (GET_MODE (diff), PLUS, - diff, GEN_INT (abs_inc - 1), - diff, 1, OPTAB_LIB_WIDEN); - else - 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) */ + 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); @@ -740,7 +738,7 @@ doloop_modify_runtime (loop, iterations_max, } } - sequence = gen_sequence (); + sequence = get_insns (); end_sequence (); emit_insn_before (sequence, loop->start); @@ -755,7 +753,7 @@ doloop_modify_runtime (loop, iterations_max, 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 non-zero if loop + is a candidate for this optimization. Returns nonzero if loop successfully modified. */ int doloop_optimize (loop) @@ -794,7 +792,7 @@ doloop_optimize (loop) &increment, &mode)) { if (loop_dump_stream) - fprintf (loop_dump_stream, + fprintf (loop_dump_stream, "Doloop: Cannot precondition loop.\n"); return 0; } @@ -864,18 +862,19 @@ doloop_optimize (loop) return 0; } - /* A raw define_insn may yield a plain pattern. If a sequence - was involved, the last must be the jump instruction. */ - if (GET_CODE (doloop_seq) == SEQUENCE) + /* 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)) { - doloop_pat = XVECEXP (doloop_seq, 0, XVECLEN (doloop_seq, 0) - 1); + 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; } - else - doloop_pat = doloop_seq; if (! doloop_pat || ! (condition = doloop_condition_get (doloop_pat))) |
