For fast unaligned access targets, by pieces uses up to UNITS_PER_WORD
size pieces resulting in more store instructions than needed. For
example gcc.target/riscv/rvv/base/setmem-2.c:f1 built with
`-O3 -march=rv64gcv -mtune=thead-c906`:
```
f1:
vsetivli zero,8,e8,mf2,ta,ma
vmv.v.x v1,a1
vsetivli zero,0,e32,mf2,ta,ma
sb a1,14(a0)
vmv.x.s a4,v1
vsetivli zero,8,e16,m1,ta,ma
vmv.x.s a5,v1
vse8.v v1,0(a0)
sw a4,8(a0)
sh a5,12(a0)
ret
```
The slow unaligned access version built with `-O3 -march=rv64gcv` used
15 sb instructions:
```
f1:
sb a1,0(a0)
sb a1,1(a0)
sb a1,2(a0)
sb a1,3(a0)
sb a1,4(a0)
sb a1,5(a0)
sb a1,6(a0)
sb a1,7(a0)
sb a1,8(a0)
sb a1,9(a0)
sb a1,10(a0)
sb a1,11(a0)
sb a1,12(a0)
sb a1,13(a0)
sb a1,14(a0)
ret
```
After this patch, the following is generated in both cases:
```
f1:
vsetivli zero,15,e8,m1,ta,ma
vmv.v.x v1,a1
vse8.v v1,0(a0)
ret
```
gcc/ChangeLog:
* config/riscv/riscv.cc (riscv_use_by_pieces_infrastructure_p):
New function.
(TARGET_USE_BY_PIECES_INFRASTRUCTURE_P): Define.
gcc/testsuite/ChangeLog:
* gcc.target/riscv/rvv/autovec/pr113469.c: Expect mf2 setmem.
* gcc.target/riscv/rvv/base/setmem-2.c: Update f1 to expect
straight-line vector memset.
* gcc.target/riscv/rvv/base/setmem-3.c: Likewise.
---
gcc/config/riscv/riscv.cc | 19 +++++++++++++++++++
.../gcc.target/riscv/rvv/autovec/pr113469.c | 3 ++-
.../gcc.target/riscv/rvv/base/setmem-2.c | 12 +++++++-----
.../gcc.target/riscv/rvv/base/setmem-3.c | 12 +++++++-----
4 files changed, 35 insertions(+), 11 deletions(-)
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 0b3b2c4cba9..2e9ac280c8f 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -12695,6 +12695,22 @@ riscv_stack_clash_protection_alloca_probe_range (void)
return STACK_CLASH_CALLER_GUARD;
}
+static bool
+riscv_use_by_pieces_infrastructure_p (unsigned HOST_WIDE_INT size,
+ unsigned alignment,
+ enum by_pieces_operation op, bool speed_p)
+{
+ /* For set/clear with size > UNITS_PER_WORD, by pieces uses vector broadcasts
+ with UNITS_PER_WORD size pieces. Use setmem<mode> instead which can use
+ bigger chunks. */
+ if (TARGET_VECTOR && stringop_strategy & STRATEGY_VECTOR
+ && (op == CLEAR_BY_PIECES || op == SET_BY_PIECES)
+ && speed_p && size > UNITS_PER_WORD)
+ return false;
+
+ return default_use_by_pieces_infrastructure_p (size, alignment, op, speed_p);
+}
+
/* Initialize the GCC target structure. */
#undef TARGET_ASM_ALIGNED_HI_OP
#define TARGET_ASM_ALIGNED_HI_OP "\t.half\t"
@@ -13060,6 +13076,9 @@ riscv_stack_clash_protection_alloca_probe_range (void)
#undef TARGET_C_MODE_FOR_FLOATING_TYPE
#define TARGET_C_MODE_FOR_FLOATING_TYPE riscv_c_mode_for_floating_type
+#undef TARGET_USE_BY_PIECES_INFRASTRUCTURE_P
+#define TARGET_USE_BY_PIECES_INFRASTRUCTURE_P
riscv_use_by_pieces_infrastructure_p
+
struct gcc_target targetm = TARGET_INITIALIZER;
#include "gt-riscv.h"
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr113469.c
b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr113469.c
index d1c118c02d6..f86084bdb40 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr113469.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr113469.c
@@ -51,4 +51,5 @@ void p(int buf, __builtin_va_list ab, int q) {
} while (k);
}
-/* { dg-final { scan-assembler-times
{vsetivli\tzero,\s*4,\s*e8,\s*mf4,\s*t[au],\s*m[au]} 2 } } */
+/* { dg-final { scan-assembler-times
{vsetivli\tzero,\s*4,\s*e8,\s*mf4,\s*t[au],\s*m[au]} 1 } } */
+/* { dg-final { scan-assembler-times
{vsetivli\tzero,\s*8,\s*e8,\s*mf2,\s*t[au],\s*m[au]} 1 } } */
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/setmem-2.c
b/gcc/testsuite/gcc.target/riscv/rvv/base/setmem-2.c
index faea442a4bd..838fbebadff 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/base/setmem-2.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/base/setmem-2.c
@@ -5,15 +5,17 @@
#define MIN_VECTOR_BYTES (__riscv_v_min_vlen / 8)
-/* Small memsets shouldn't be vectorised.
+/* Vectorise with no loop.
** f1:
** (
-** sb\s+a1,0\(a0\)
-** ...
+** vsetivli\s+zero,\d+,e8,m1,ta,ma
** |
-** li\s+a2,\d+
-** tail\s+memset
+** li\s+a\d+,\d+
+** vsetvli\s+zero,a\d+,e8,m1,ta,ma
** )
+** vmv\.v\.x\s+v\d+,a1
+** vse8\.v\s+v\d+,0\(a0\)
+** ret
*/
void *
f1 (void *a, int const b)
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/base/setmem-3.c
b/gcc/testsuite/gcc.target/riscv/rvv/base/setmem-3.c
index 52766fece76..44933819715 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/base/setmem-3.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/base/setmem-3.c
@@ -5,15 +5,17 @@
#define MIN_VECTOR_BYTES (__riscv_v_min_vlen / 8)
-/* Small memsets shouldn't be vectorised.
+/* Vectorise with no loop.
** f1:
** (
-** sb\s+a1,0\(a0\)
-** ...
+** vsetivli\s+zero,\d+,e8,m1,ta,ma
** |
-** li\s+a2,\d+
-** tail\s+memset
+** li\s+a\d+,\d+
+** vsetvli\s+zero,a\d+,e8,m1,ta,ma
** )
+** vmv\.v\.x\s+v\d+,a1
+** vse8\.v\s+v\d+,0\(a0\)
+** ret
*/
void *
f1 (void *a, int const b)
--
2.43.0
