Richard Biener <richard.guent...@gmail.com> writes:
> On Fri, Jul 20, 2018 at 12:57 PM Richard Sandiford
> <richard.sandif...@arm.com> wrote:
>>
>> We could vectorise:
>>
>> for (...)
>> {
>> a[0] = ...;
>> a[1] = ...;
>> a[2] = ...;
>> a[3] = ...;
>> a += stride;
>> }
>>
>> (including the case when stride == 8) but not:
>>
>> for (...)
>> {
>> a[0] = ...;
>> a[1] = ...;
>> a[2] = ...;
>> a[3] = ...;
>> a += 8;
>> }
>>
>> (where the stride is always 8). The former was treated as a "grouped
>> and strided" store, while the latter was treated as grouped store with
>> gaps, which we don't support.
>>
>> This patch makes us treat groups of stores with gaps at the end as
>> strided groups too. I tried to go through all uses of STMT_VINFO_STRIDED_P
>> and all vector uses of DR_STEP to see whether there were any hard-baked
>> assumptions, but couldn't see any. I wondered whether we should relax:
>>
>> /* We do not have to consider dependences between accesses that belong
>> to the same group, unless the stride could be smaller than the
>> group size. */
>> if (DR_GROUP_FIRST_ELEMENT (stmtinfo_a)
>> && (DR_GROUP_FIRST_ELEMENT (stmtinfo_a)
>> == DR_GROUP_FIRST_ELEMENT (stmtinfo_b))
>> && !STMT_VINFO_STRIDED_P (stmtinfo_a))
>> return false;
>>
>> for cases in which the step is constant and the absolute step is known
>> to be greater than the group size, but data dependence analysis should
>> already return chrec_known for those cases.
>>
>> The new test is a version of vect-avg-15.c with the variable step
>> replaced by a constant one.
>>
>> A natural follow-on would be to do the same for groups with gaps in
>> the middle:
>>
>> /* Check that the distance between two accesses is equal to the
>> type
>> size. Otherwise, we have gaps. */
>> diff = (TREE_INT_CST_LOW (DR_INIT (data_ref))
>> - TREE_INT_CST_LOW (prev_init)) / type_size;
>> if (diff != 1)
>> {
>> [...]
>> if (DR_IS_WRITE (data_ref))
>> {
>> if (dump_enabled_p ())
>> dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
>> "interleaved store with gaps\n");
>> return false;
>> }
>>
>> But I think we should do that separately and see what the fallout
>> from this change is first.
>
> Agreed.
>
>> Tested on aarch64-linux-gnu (with and without SVE), aarch64_be-elf
>> and x86_64-linux-gnu. OK to install?
>
> Do you need to set STMT_VINFO_STRIDED_P on all stmts? I think
> it is enough to set it on the first group element.
>
> OK otherwise.
Thanks. Here's what I installed after fixing the STMT_VINFO_STRIDED_P
uses in get_load_store_type.
Richard
2018-08-22 Richard Sandiford <richard.sandif...@arm.com>
gcc/
* tree-vect-data-refs.c (vect_analyze_group_access_1): Convert
grouped stores with gaps to a strided group.
gcc/testsuite/
* gcc.dg/vect/vect-avg-16.c: New test.
* gcc.dg/vect/slp-37.c: Expect the loop to be vectorized.
* gcc.dg/vect/vect-strided-u8-i8-gap4.c,
* gcc.dg/vect/vect-strided-u8-i8-gap4-big-array.c: Likewise for
the second loop in main1.
Index: gcc/tree-vect-data-refs.c
===================================================================
--- gcc/tree-vect-data-refs.c 2018-08-21 14:47:07.795167843 +0100
+++ gcc/tree-vect-data-refs.c 2018-08-22 10:24:22.070479189 +0100
@@ -2633,10 +2633,8 @@ vect_analyze_group_access_1 (dr_vec_info
if (groupsize != count
&& !DR_IS_READ (dr))
{
- if (dump_enabled_p ())
- dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
- "interleaved store with gaps\n");
- return false;
+ groupsize = count;
+ STMT_VINFO_STRIDED_P (stmt_info) = true;
}
/* If there is a gap after the last load in the group it is the
@@ -2652,6 +2650,8 @@ vect_analyze_group_access_1 (dr_vec_info
"Detected interleaving ");
if (DR_IS_READ (dr))
dump_printf (MSG_NOTE, "load ");
+ else if (STMT_VINFO_STRIDED_P (stmt_info))
+ dump_printf (MSG_NOTE, "strided store ");
else
dump_printf (MSG_NOTE, "store ");
dump_printf (MSG_NOTE, "of size %u starting with ",
Index: gcc/testsuite/gcc.dg/vect/vect-avg-16.c
===================================================================
--- /dev/null 2018-07-26 10:26:13.137955424 +0100
+++ gcc/testsuite/gcc.dg/vect/vect-avg-16.c 2018-08-22 10:24:22.070479189
+0100
@@ -0,0 +1,52 @@
+/* { dg-additional-options "-O3" } */
+/* { dg-require-effective-target vect_int } */
+
+#include "tree-vect.h"
+
+#define N 80
+
+void __attribute__ ((noipa))
+f (signed char *restrict a, signed char *restrict b,
+ signed char *restrict c, int n)
+{
+ for (int j = 0; j < n; ++j)
+ {
+ for (int i = 0; i < 16; ++i)
+ a[i] = (b[i] + c[i]) >> 1;
+ a += 20;
+ b += 20;
+ c += 20;
+ }
+}
+
+#define BASE1 -126
+#define BASE2 -42
+
+signed char a[N], b[N], c[N];
+
+int
+main (void)
+{
+ check_vect ();
+
+ for (int i = 0; i < N; ++i)
+ {
+ a[i] = i;
+ b[i] = BASE1 + i * 3;
+ c[i] = BASE2 + i * 2;
+ asm volatile ("" ::: "memory");
+ }
+ f (a, b, c, N / 20);
+ for (int i = 0; i < N; ++i)
+ {
+ int d = (BASE1 + BASE2 + i * 5) >> 1;
+ if (a[i] != (i % 20 < 16 ? d : i))
+ __builtin_abort ();
+ }
+ return 0;
+}
+
+/* { dg-final { scan-tree-dump "vect_recog_average_pattern: detected" "vect" }
} */
+/* { dg-final { scan-tree-dump {\.AVG_FLOOR} "vect" { target vect_avg_qi } } }
*/
+/* { dg-final { scan-tree-dump "Loop contains only SLP stmts" "vect" { target
vect_avg_qi } } } */
+/* { dg-final { scan-tree-dump-times "vectorized 1 loop" 1 "vect" { target
vect_avg_qi } } } */
Index: gcc/testsuite/gcc.dg/vect/slp-37.c
===================================================================
--- gcc/testsuite/gcc.dg/vect/slp-37.c 2018-08-01 10:55:10.000000000 +0100
+++ gcc/testsuite/gcc.dg/vect/slp-37.c 2018-08-22 10:24:22.070479189 +0100
@@ -17,8 +17,8 @@ foo1 (s1 *arr)
int i;
s1 *ptr = arr;
- /* Different constant types - not SLPable. The group size is not power of 2,
- interleaving is not supported either. */
+ /* Vectorized as a strided SLP pair of accesses to <a, b> and a single
+ strided access to c. */
for (i = 0; i < N; i++)
{
ptr->a = 6;
@@ -58,6 +58,5 @@ int main (void)
return 0;
}
-/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 0 "vect" } } */
-/* { dg-final { scan-tree-dump-times "vectorizing stmts using SLP" 0 "vect" }
} */
-
+/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" } } */
+/* { dg-final { scan-tree-dump-times "vectorizing stmts using SLP" 1 "vect" }
} */
Index: gcc/testsuite/gcc.dg/vect/vect-strided-u8-i8-gap4.c
===================================================================
--- gcc/testsuite/gcc.dg/vect/vect-strided-u8-i8-gap4.c 2018-08-01
10:55:10.000000000 +0100
+++ gcc/testsuite/gcc.dg/vect/vect-strided-u8-i8-gap4.c 2018-08-22
10:24:22.070479189 +0100
@@ -53,7 +53,7 @@ main1 (s *arr)
}
ptr = arr;
- /* Not vectorizable: gap in store. */
+ /* Vectorized as a strided SLP pair. */
for (i = 0; i < N; i++)
{
res[i].a = ptr->b;
@@ -97,5 +97,4 @@ int main (void)
return 0;
}
-/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" { target
vect_strided8 } } } */
-
+/* { dg-final { scan-tree-dump-times "vectorized 2 loops" 1 "vect" { target
vect_strided8 } } } */
Index: gcc/testsuite/gcc.dg/vect/vect-strided-u8-i8-gap4-big-array.c
===================================================================
--- gcc/testsuite/gcc.dg/vect/vect-strided-u8-i8-gap4-big-array.c
2018-08-01 10:55:10.000000000 +0100
+++ gcc/testsuite/gcc.dg/vect/vect-strided-u8-i8-gap4-big-array.c
2018-08-22 10:24:22.070479189 +0100
@@ -55,7 +55,7 @@ main1 (s *arr)
}
ptr = arr;
- /* Not vectorizable: gap in store. */
+ /* Vectorized as a strided SLP pair. */
for (i = 0; i < N; i++)
{
res[i].a = ptr->b;
@@ -110,5 +110,4 @@ int main (void)
return 0;
}
-/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" { target
vect_strided8 } } } */
-
+/* { dg-final { scan-tree-dump-times "vectorized 2 loops" 1 "vect" { target
vect_strided8 } } } */
