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| author | Corey Minyard <minyard@acm.org> | 2001-11-27 18:30:40 +0000 |
|---|---|---|
| committer | Richard Henderson <rth@gcc.gnu.org> | 2001-11-27 10:30:40 -0800 |
| commit | ec3fba5614d0ac97acf5a60164a4fdc0ad21791f (patch) | |
| tree | c922a76f1382f72691ef5b5d6b95f6ea94186174 /gcc | |
| parent | b856c15d7e97280853a83042ccb3ba29c79e7e9f (diff) | |
| download | gcc-ec3fba5614d0ac97acf5a60164a4fdc0ad21791f.zip gcc-ec3fba5614d0ac97acf5a60164a4fdc0ad21791f.tar.gz gcc-ec3fba5614d0ac97acf5a60164a4fdc0ad21791f.tar.bz2 | |
unroll.c (loop_iterations): Detect one situation in which we overestimate the number of iterations.
* unroll.c (loop_iterations): Detect one situation in which we
overestimate the number of iterations.
Co-Authored-By: Richard Henderson <rth@redhat.com>
From-SVN: r47386
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 6 | ||||
| -rw-r--r-- | gcc/unroll.c | 35 |
2 files changed, 41 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index b118193..00e6134 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2001-11-17 Corey Minyard <minyard@acm.org> + Richard Henderson <rth@redhat.com> + + * unroll.c (loop_iterations): Detect one situation in which we + overestimate the number of iterations. + 2001-11-27 Rainer Orth <ro@TechFak.Uni-Bielefeld.DE> * gcc.c (set_input): Export. 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) |