On Tue, Mar 18, 2014 at 4:43 AM, Richard Biener <rguent...@suse.de> wrote: > > On Mon, 17 Mar 2014, Cong Hou wrote: > > > On Mon, Mar 17, 2014 at 6:44 AM, Richard Biener <rguent...@suse.de> wrote: > > > On Fri, 14 Mar 2014, Cong Hou wrote: > > > > > >> On Fri, Mar 14, 2014 at 12:58 AM, Richard Biener <rguent...@suse.de> > > >> wrote: > > >> > On Fri, 14 Mar 2014, Jakub Jelinek wrote: > > >> > > > >> >> On Fri, Mar 14, 2014 at 08:52:07AM +0100, Richard Biener wrote: > > >> >> > > Consider this fact and if there are alias checks, we can safely > > >> >> > > remove > > >> >> > > the epilogue if the maximum trip count of the loop is less than or > > >> >> > > equal to the calculated threshold. > > >> >> > > > >> >> > You have to consider n % vf != 0, so an argument on only maximum > > >> >> > trip count or threshold cannot work. > > >> >> > > >> >> Well, if you only check if maximum trip count is <= vf and you know > > >> >> that for n < vf the vectorized loop + it's epilogue path will not be > > >> >> taken, > > >> >> then perhaps you could, but it is a very special case. > > >> >> Now, the question is when we are guaranteed we enter the scalar > > >> >> versioned > > >> >> loop instead for n < vf, is that in case of versioning for alias or > > >> >> versioning for alignment? > > >> > > > >> > I think neither - I have plans to do the cost model check together > > >> > with the versioning condition but didn't get around to implement that. > > >> > That would allow stronger max bounds for the epilogue loop. > > >> > > >> In vect_transform_loop(), check_profitability will be set to true if > > >> th >= VF-1 and the number of iteration is unknown (we only consider > > >> unknown trip count here), where th is calculated based on the > > >> parameter PARAM_MIN_VECT_LOOP_BOUND and cost model, with the minimum > > >> value VF-1. If the loop needs to be versioned, then > > >> check_profitability with true value will be passed to > > >> vect_loop_versioning(), in which an enhanced loop bound check > > >> (considering cost) will be built. So I think if the loop is versioned > > >> and n < VF, then we must enter the scalar version, and in this case > > >> removing epilogue should be safe when the maximum trip count <= th+1. > > > > > > You mean exactly in the case where the profitability check ensures > > > that n % vf == 0? Thus effectively if n == maximum trip count? > > > That's quite a special case, no? > > > > > > Yes, it is a special case. But it is in this special case that those > > warnings are thrown out. Also, I think declaring an array with VF*N as > > length is not unusual. > > Ok, but then for the patch compute the cost model threshold once > in vect_analyze_loop_2 and store it in a new > LOOP_VINFO_COST_MODEL_THRESHOLD.
Done. > Also you have to check > the return value from max_stmt_executions_int as that may return > -1 if the number cannot be computed (or isn't representable in > a HOST_WIDE_INT). It will be converted to unsigned type so that -1 means infinity. > You also should check for > LOOP_REQUIRES_VERSIONING_FOR_ALIGNMENT which should have the > same effect on the cost model check. Done. > > > The existing condition is already complicated enough - adding new > stuff warrants comments before the (sub-)checks. OK. Comments added. Below is the revised patch. Bootstrapped and tested on a x86-64 machine. Cong diff --git a/gcc/ChangeLog b/gcc/ChangeLog index e1d8666..eceefb3 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,18 @@ +2014-03-11 Cong Hou <co...@google.com> + + PR tree-optimization/60505 + * tree-vectorizer.h (struct _stmt_vec_info): Add th field as the + threshold of number of iterations below which no vectorization will be + done. + * tree-vect-loop.c (new_loop_vec_info): + Initialize LOOP_VINFO_COST_MODEL_THRESHOLD. + * tree-vect-loop.c (vect_analyze_loop_operations): + Set LOOP_VINFO_COST_MODEL_THRESHOLD. + * tree-vect-loop.c (vect_transform_loop): + Use LOOP_VINFO_COST_MODEL_THRESHOLD. + * tree-vect-loop.c (vect_analyze_loop_2): Check the maximum number + of iterations of the loop and see if we should build the epilogue. + 2014-03-10 Jakub Jelinek <ja...@redhat.com> PR ipa/60457 diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 41b6875..09ec1c0 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2014-03-11 Cong Hou <co...@google.com> + + PR tree-optimization/60505 + * gcc.dg/vect/pr60505.c: New test. + 2014-03-10 Jakub Jelinek <ja...@redhat.com> PR ipa/60457 diff --git a/gcc/testsuite/gcc.dg/vect/pr60505.c b/gcc/testsuite/gcc.dg/vect/pr60505.c new file mode 100644 index 0000000..6940513 --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/pr60505.c @@ -0,0 +1,12 @@ +/* { dg-do compile } */ +/* { dg-additional-options "-Wall -Werror" } */ + +void foo(char *in, char *out, int num) +{ + int i; + char ovec[16] = {0}; + + for(i = 0; i < num ; ++i) + out[i] = (ovec[i] = in[i]); + out[num] = ovec[num/2]; +} diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c index df6ab6f..1c78e11 100644 --- a/gcc/tree-vect-loop.c +++ b/gcc/tree-vect-loop.c @@ -933,6 +933,7 @@ new_loop_vec_info (struct loop *loop) LOOP_VINFO_NITERS (res) = NULL; LOOP_VINFO_NITERS_UNCHANGED (res) = NULL; LOOP_VINFO_COST_MODEL_MIN_ITERS (res) = 0; + LOOP_VINFO_COST_MODEL_THRESHOLD (res) = 0; LOOP_VINFO_VECTORIZABLE_P (res) = 0; LOOP_VINFO_PEELING_FOR_ALIGNMENT (res) = 0; LOOP_VINFO_VECT_FACTOR (res) = 0; @@ -1579,6 +1580,8 @@ vect_analyze_loop_operations (loop_vec_info loop_vinfo, bool slp) || min_profitable_iters > min_scalar_loop_bound)) th = (unsigned) min_profitable_iters; + LOOP_VINFO_COST_MODEL_THRESHOLD (loop_vinfo) = th; + if (LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo) && LOOP_VINFO_INT_NITERS (loop_vinfo) <= th) { @@ -1625,6 +1628,7 @@ vect_analyze_loop_2 (loop_vec_info loop_vinfo) bool ok, slp = false; int max_vf = MAX_VECTORIZATION_FACTOR; int min_vf = 2; + unsigned int th; /* Find all data references in the loop (which correspond to vdefs/vuses) and analyze their evolution in the loop. Also adjust the minimal @@ -1769,6 +1773,10 @@ vect_analyze_loop_2 (loop_vec_info loop_vinfo) /* Decide whether we need to create an epilogue loop to handle remaining scalar iterations. */ + th = ((LOOP_VINFO_COST_MODEL_THRESHOLD (loop_vinfo) + 1) + / LOOP_VINFO_VECT_FACTOR (loop_vinfo)) + * LOOP_VINFO_VECT_FACTOR (loop_vinfo); + if (LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo) && LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo) > 0) { @@ -1779,7 +1787,14 @@ vect_analyze_loop_2 (loop_vec_info loop_vinfo) } else if (LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo) || (tree_ctz (LOOP_VINFO_NITERS (loop_vinfo)) - < (unsigned)exact_log2 (LOOP_VINFO_VECT_FACTOR (loop_vinfo)))) + < (unsigned)exact_log2 (LOOP_VINFO_VECT_FACTOR (loop_vinfo)) + /* In case of versioning, check if the maximum number of + iterations is greater than th. If they are identical, + the epilogue is unnecessary. */ + && ((!LOOP_REQUIRES_VERSIONING_FOR_ALIAS (loop_vinfo) + && !LOOP_REQUIRES_VERSIONING_FOR_ALIGNMENT (loop_vinfo)) + || (unsigned HOST_WIDE_INT)max_stmt_executions_int + (LOOP_VINFO_LOOP (loop_vinfo)) > th))) LOOP_VINFO_PEELING_FOR_NITER (loop_vinfo) = true; /* If an epilogue loop is required make sure we can create one. */ @@ -5775,9 +5790,7 @@ vect_transform_loop (loop_vec_info loop_vinfo) by our caller. If the threshold makes all loops profitable that run at least the vectorization factor number of times checking is pointless, too. */ - th = ((PARAM_VALUE (PARAM_MIN_VECT_LOOP_BOUND) - * LOOP_VINFO_VECT_FACTOR (loop_vinfo)) - 1); - th = MAX (th, LOOP_VINFO_COST_MODEL_MIN_ITERS (loop_vinfo)); + th = LOOP_VINFO_COST_MODEL_THRESHOLD (loop_vinfo); if (th >= LOOP_VINFO_VECT_FACTOR (loop_vinfo) - 1 && !LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)) { diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h index f8efe47..f2087e2 100644 --- a/gcc/tree-vectorizer.h +++ b/gcc/tree-vectorizer.h @@ -264,6 +264,11 @@ typedef struct _loop_vec_info { values unknown at compile time. */ int min_profitable_iters; + /* Threshold of number of iterations below which vectorzation will not be + performed. It is calculated from MIN_PROFITABLE_ITERS and + PARAM_MIN_VECT_LOOP_BOUND. */ + unsigned int th; + /* Is the loop vectorizable? */ bool vectorizable; @@ -382,6 +387,7 @@ typedef struct _loop_vec_info { cost model. */ #define LOOP_VINFO_NITERS_UNCHANGED(L) (L)->num_iters_unchanged #define LOOP_VINFO_COST_MODEL_MIN_ITERS(L) (L)->min_profitable_iters +#define LOOP_VINFO_COST_MODEL_THRESHOLD(L) (L)->th #define LOOP_VINFO_VECTORIZABLE_P(L) (L)->vectorizable #define LOOP_VINFO_VECT_FACTOR(L) (L)->vectorization_factor #define LOOP_VINFO_PTR_MASK(L) (L)->ptr_mask > > > Richard.