diff options
Diffstat (limited to 'gcc/unroll.c')
| -rw-r--r-- | gcc/unroll.c | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/gcc/unroll.c b/gcc/unroll.c index 4b7dd97..35ce939 100644 --- a/gcc/unroll.c +++ b/gcc/unroll.c @@ -3706,6 +3706,41 @@ loop_iterations (loop) if (initial_value == 0) return 0; + /* 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 initial value to compensate. */ + + if (loop->scan_start && loop->cont + && INSN_LUID (loop->scan_start) < INSN_LUID (loop->cont) + && INSN_LUID (bl->biv->insn) < INSN_LUID (loop->scan_start)) + { + if (loop_dump_stream) + fprintf (loop_dump_stream, + "Loop iterations: Basic induction var skips initial incr.\n"); + if (GET_CODE (increment) != CONST_INT) + { + if (loop_dump_stream) + fprintf (loop_dump_stream, + "Loop iterations: Can't adjust with non-constant incr.\n"); + return 0; + } + initial_value = plus_constant (initial_value, -INTVAL (increment)); + } + unsigned_p = 0; off_by_one = 0; switch (comparison_code) |