On Wed, 18 Apr 2012, Richard Guenther wrote:
>
> This teaches loop-iv (RTL IV analysis) about loop->nb_iterations_upper_bound.
> It avoids poinless unrolling of vectorizer prologue loops for now.
>
> Bootstrap and regtest pending on x86_64-unknown-linux-gnu.
Finished. Needs the following testsuite adjustment
* gcc.dg/var-expand1.c: Increase array size to make unrolling
possibly profitable.
Index: gcc/testsuite/gcc.dg/var-expand1.c
===================================================================
--- gcc/testsuite/gcc.dg/var-expand1.c.orig 2012-04-19
10:45:32.000000000 +0200
+++ gcc/testsuite/gcc.dg/var-expand1.c 2012-04-19 10:45:43.475201279
+0200
@@ -6,7 +6,7 @@
extern void abort (void);
-float array[10] = { 1,2,3,4,5,6,7,8,9,10 };
+float array[30] = { 1,2,3,4,5,6,7,8,9,10 };
int foo (int n)
{
because otherwise we see that the loop rolls at most 10 times
and thus unrolling by a factor of 8 is pointless (well, yes, we
are somewhat inflexible with the amount of unrolling here).
Committed.
Richard.
> Richard.
>
> 2012-04-18 Richard Guenther <rguent...@suse.de>
>
> PR rtl-optimization/44688
> * loop-iv.c (determine_max_iter): Only return max_iter.
> (iv_number_of_iterations): Also use the recorded loop bound
> on the maximum number of iterations.
> * loop-unroll.c (decide_unroll_runtime_iterations): Use
> max_iter to avoid unrolling loops that do not roll.
> (decide_unroll_stupid): Likewise.
>
> Index: gcc/loop-iv.c
> ===================================================================
> *** gcc/loop-iv.c.orig 2012-04-18 15:29:39.000000000 +0200
> --- gcc/loop-iv.c 2012-04-18 16:03:21.911222247 +0200
> *************** canonicalize_iv_subregs (struct rtx_iv *
> *** 2190,2197 ****
> return true;
> }
>
> ! /* Tries to estimate the maximum number of iterations in LOOP, and store the
> ! result in DESC. This function is called from iv_number_of_iterations
> with
> a number of fields in DESC already filled in. OLD_NITER is the original
> expression for the number of iterations, before we tried to simplify it.
> */
>
> --- 2190,2197 ----
> return true;
> }
>
> ! /* Tries to estimate the maximum number of iterations in LOOP, and return
> the
> ! result. This function is called from iv_number_of_iterations with
> a number of fields in DESC already filled in. OLD_NITER is the original
> expression for the number of iterations, before we tried to simplify it.
> */
>
> *************** determine_max_iter (struct loop *loop, s
> *** 2207,2216 ****
> {
> nmax = INTVAL (XEXP (niter, 0));
> if (!(nmax & (nmax + 1)))
> ! {
> ! desc->niter_max = nmax;
> ! return nmax;
> ! }
> }
>
> get_mode_bounds (desc->mode, desc->signed_p, desc->mode, &mmin, &mmax);
> --- 2207,2213 ----
> {
> nmax = INTVAL (XEXP (niter, 0));
> if (!(nmax & (nmax + 1)))
> ! return nmax;
> }
>
> get_mode_bounds (desc->mode, desc->signed_p, desc->mode, &mmin, &mmax);
> *************** determine_max_iter (struct loop *loop, s
> *** 2219,2228 ****
> if (GET_CODE (niter) == UDIV)
> {
> if (!CONST_INT_P (XEXP (niter, 1)))
> ! {
> ! desc->niter_max = nmax;
> ! return nmax;
> ! }
> inc = INTVAL (XEXP (niter, 1));
> niter = XEXP (niter, 0);
> }
> --- 2216,2222 ----
> if (GET_CODE (niter) == UDIV)
> {
> if (!CONST_INT_P (XEXP (niter, 1)))
> ! return nmax;
> inc = INTVAL (XEXP (niter, 1));
> niter = XEXP (niter, 0);
> }
> *************** determine_max_iter (struct loop *loop, s
> *** 2241,2247 ****
> if (dump_file)
> fprintf (dump_file, ";; improved upper bound by one.\n");
> }
> - desc->niter_max = nmax / inc;
> return nmax / inc;
> }
>
> --- 2235,2240 ----
> *************** iv_number_of_iterations (struct loop *lo
> *** 2259,2265 ****
> enum rtx_code cond;
> enum machine_mode mode, comp_mode;
> rtx mmin, mmax, mode_mmin, mode_mmax;
> ! unsigned HOST_WIDEST_INT s, size, d, inv;
> HOST_WIDEST_INT up, down, inc, step_val;
> int was_sharp = false;
> rtx old_niter;
> --- 2252,2258 ----
> enum rtx_code cond;
> enum machine_mode mode, comp_mode;
> rtx mmin, mmax, mode_mmin, mode_mmax;
> ! unsigned HOST_WIDEST_INT s, size, d, inv, max;
> HOST_WIDEST_INT up, down, inc, step_val;
> int was_sharp = false;
> rtx old_niter;
> *************** iv_number_of_iterations (struct loop *lo
> *** 2279,2284 ****
> --- 2272,2280 ----
> desc->const_iter = false;
> desc->niter_expr = NULL_RTX;
> desc->niter_max = 0;
> + if (loop->any_upper_bound
> + && double_int_fits_in_uhwi_p (loop->nb_iterations_upper_bound))
> + desc->niter_max = loop->nb_iterations_upper_bound.low;
>
> cond = GET_CODE (condition);
> gcc_assert (COMPARISON_P (condition));
> *************** iv_number_of_iterations (struct loop *lo
> *** 2547,2553 ****
> down = INTVAL (CONST_INT_P (iv0.base)
> ? iv0.base
> : mode_mmin);
> ! desc->niter_max = (up - down) / inc + 1;
>
> if (iv0.step == const0_rtx)
> {
> --- 2543,2552 ----
> down = INTVAL (CONST_INT_P (iv0.base)
> ? iv0.base
> : mode_mmin);
> ! max = (up - down) / inc + 1;
> ! if (!desc->niter_max
> ! || max < desc->niter_max)
> ! desc->niter_max = max;
>
> if (iv0.step == const0_rtx)
> {
> *************** iv_number_of_iterations (struct loop *lo
> *** 2762,2769 ****
> }
> else
> {
> ! if (!desc->niter_max)
> ! desc->niter_max = determine_max_iter (loop, desc, old_niter);
>
> /* simplify_using_initial_values does a copy propagation on the
> registers
> in the expression for the number of iterations. This prolongs life
> --- 2761,2770 ----
> }
> else
> {
> ! max = determine_max_iter (loop, desc, old_niter);
> ! if (!desc->niter_max
> ! || max < desc->niter_max)
> ! desc->niter_max = max;
>
> /* simplify_using_initial_values does a copy propagation on the
> registers
> in the expression for the number of iterations. This prolongs life
> Index: gcc/loop-unroll.c
> ===================================================================
> *** gcc/loop-unroll.c.orig 2012-04-18 15:29:39.000000000 +0200
> --- gcc/loop-unroll.c 2012-04-18 16:10:24.444196989 +0200
> *************** decide_unroll_runtime_iterations (struct
> *** 857,863 ****
> }
>
> /* If we have profile feedback, check whether the loop rolls. */
> ! if (loop->header->count && expected_loop_iterations (loop) < 2 * nunroll)
> {
> if (dump_file)
> fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n");
> --- 857,865 ----
> }
>
> /* If we have profile feedback, check whether the loop rolls. */
> ! if ((loop->header->count
> ! && expected_loop_iterations (loop) < 2 * nunroll)
> ! || desc->niter_max < 2 * nunroll)
> {
> if (dump_file)
> fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n");
> *************** decide_unroll_stupid (struct loop *loop,
> *** 1400,1407 ****
> }
>
> /* If we have profile feedback, check whether the loop rolls. */
> ! if (loop->header->count
> ! && expected_loop_iterations (loop) < 2 * nunroll)
> {
> if (dump_file)
> fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n");
> --- 1402,1410 ----
> }
>
> /* If we have profile feedback, check whether the loop rolls. */
> ! if ((loop->header->count
> ! && expected_loop_iterations (loop) < 2 * nunroll)
> ! || desc->niter_max < 2 * nunroll)
> {
> if (dump_file)
> fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n");
>
--
Richard Guenther <rguent...@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer
