[v2] RISC-V: Bugfix for vec_init repeating auto vectorization in RV32

  From: Pan Li <pan2.li@intel.com>

This patch would like to fix one bug exported by RV32 test case
multiple_rgroup_run-2.c. The mask should be restricted by elen in
vector, and the condition between the vmv.s.x and the vmv.v.x should
take inner_bits_size rather than constants.

After this patch, below failures on RV32 will be fixed.

FAIL: gcc.target/riscv/rvv/autovec/partial/multiple_rgroup_run-2.c execution test
FAIL: gcc.target/riscv/rvv/autovec/partial/multiple_rgroup_run-2.c execution test
FAIL: gcc.target/riscv/rvv/autovec/partial/multiple_rgroup_run-2.c execution test
FAIL: gcc.target/riscv/rvv/autovec/partial/multiple_rgroup_run-2.c execution test
FAIL: gcc.target/riscv/rvv/autovec/vls-vlmax/repeat_run-3.c -std=c99 -O3 -ftree-vectorize --param riscv-autovec-preference=fixed-vlmax execution test

Signed-off-by: Pan Li <pan2.li@intel.com>

gcc/ChangeLog:

	* config/riscv/riscv-v.cc (rvv_builder::get_merge_scalar_mask):
	Take elen instead of scalar BITS_PER_WORD.
	(expand_vector_init_merge_repeating_sequence): Use inner_bits_size
	instead of scaler BITS_PER_WORD.
---
 gcc/config/riscv/riscv-v.cc | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)
  

+  /* We restrict the limit to the elen of RVV. For example:
+     -march=zve32*, the ELEN is 32.
+     -march=zve64*, the ELEN is 64.
+     The related vmv.v.x/vmv.s.x is restricted to ELEN as above, we cannot
+     take care of case like below when ELEN=32
+     vsetvil e64,m1
+     vmv.v.x/vmv.s.x
+   */

The comment is not clear enough.

How about:

According to RVV ISA SPEC, ELEN = 32 when -march=zve32* and ELEN = 64 when -march=zve64*.
Since vmv.v.x/vmv.s.x can't broadcast/move 64-bit value to the vector when ELEN = 32, we restrict the LIMIT to the ELEN.

I am not the native English speaker, I'd like to see Jeff or Robin comments that.

Thanks. 


juzhe.zhong@rivai.ai
 
From: pan2.li
Date: 2023-06-14 15:29
To: gcc-patches
CC: juzhe.zhong; rdapp.gcc; jeffreyalaw; pan2.li; yanzhang.wang; kito.cheng
Subject: [PATCH v2] RISC-V: Bugfix for vec_init repeating auto vectorization in RV32
From: Pan Li <pan2.li@intel.com>
 
This patch would like to fix one bug exported by RV32 test case
multiple_rgroup_run-2.c. The mask should be restricted by elen in
vector, and the condition between the vmv.s.x and the vmv.v.x should
take inner_bits_size rather than constants.
 
After this patch, below failures on RV32 will be fixed.
 
FAIL: gcc.target/riscv/rvv/autovec/partial/multiple_rgroup_run-2.c execution test
FAIL: gcc.target/riscv/rvv/autovec/partial/multiple_rgroup_run-2.c execution test
FAIL: gcc.target/riscv/rvv/autovec/partial/multiple_rgroup_run-2.c execution test
FAIL: gcc.target/riscv/rvv/autovec/partial/multiple_rgroup_run-2.c execution test
FAIL: gcc.target/riscv/rvv/autovec/vls-vlmax/repeat_run-3.c -std=c99 -O3 -ftree-vectorize --param riscv-autovec-preference=fixed-vlmax execution test
 
Signed-off-by: Pan Li <pan2.li@intel.com>
 
gcc/ChangeLog:
 
* config/riscv/riscv-v.cc (rvv_builder::get_merge_scalar_mask):
Take elen instead of scalar BITS_PER_WORD.
(expand_vector_init_merge_repeating_sequence): Use inner_bits_size
instead of scaler BITS_PER_WORD.
---
gcc/config/riscv/riscv-v.cc | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
 
diff --git a/gcc/config/riscv/riscv-v.cc b/gcc/config/riscv/riscv-v.cc
index e07d5c2901a..db1a5529419 100644
--- a/gcc/config/riscv/riscv-v.cc
+++ b/gcc/config/riscv/riscv-v.cc
@@ -399,10 +399,19 @@ rvv_builder::get_merge_scalar_mask (unsigned int index_in_pattern) const
{
   unsigned HOST_WIDE_INT mask = 0;
   unsigned HOST_WIDE_INT base_mask = (1ULL << index_in_pattern);
+  /* We restrict the limit to the elen of RVV. For example:
+     -march=zve32*, the ELEN is 32.
+     -march=zve64*, the ELEN is 64.
+     The related vmv.v.x/vmv.s.x is restricted to ELEN as above, we cannot
+     take care of case like below when ELEN=32
+     vsetvil e64,m1
+     vmv.v.x/vmv.s.x
+   */
+  unsigned int elen = TARGET_VECTOR_ELEN_64 ? 64 : 32;
-  gcc_assert (BITS_PER_WORD % npatterns () == 0);
+  gcc_assert (elen % npatterns () == 0);
-  int limit = BITS_PER_WORD / npatterns ();
+  int limit = elen / npatterns ();
   for (int i = 0; i < limit; i++)
     mask |= base_mask << (i * npatterns ());
@@ -1928,7 +1937,7 @@ expand_vector_init_merge_repeating_sequence (rtx target,
       rtx mask = gen_reg_rtx (mask_mode);
       rtx dup = gen_reg_rtx (dup_mode);
-      if (full_nelts <= BITS_PER_WORD) /* vmv.s.x.  */
+      if (full_nelts <= builder.inner_bits_size ()) /* vmv.s.x.  */
{
  rtx ops[] = {dup, gen_scalar_move_mask (dup_mask_mode),
    RVV_VUNDEF (dup_mode), merge_mask};
@@ -1938,7 +1947,8 @@ expand_vector_init_merge_repeating_sequence (rtx target,
       else /* vmv.v.x.  */
{
  rtx ops[] = {dup, force_reg (GET_MODE_INNER (dup_mode), merge_mask)};
-   rtx vl = gen_int_mode (CEIL (full_nelts, BITS_PER_WORD), Pmode);
+   rtx vl = gen_int_mode (CEIL (full_nelts, builder.inner_bits_size ()),
+ Pmode);
  emit_nonvlmax_integer_move_insn (code_for_pred_broadcast (dup_mode),
   ops, vl);
}
-- 
2.34.1
  

Hi Pan,

> This patch would like to fix one bug exported by RV32 test case
> multiple_rgroup_run-2.c. The mask should be restricted by elen in
> vector, and the condition between the vmv.s.x and the vmv.v.x should
> take inner_bits_size rather than constants.

exported -> exposed.

How about something like:

"When constructing a vector mask from individual elements we wrongly
assumed that we can broadcast BITS_PER_WORD (i.e. XLEN).  The maximum
is actually the vector element length (i.e. ELEN).  This patch fixes
this."?

> +  /* We restrict the limit to the elen of RVV. For example:
> +     -march=zve32*, the ELEN is 32.
> +     -march=zve64*, the ELEN is 64.
> +     The related vmv.v.x/vmv.s.x is restricted to ELEN as above, we cannot
> +     take care of case like below when ELEN=32
> +     vsetvil e64,m1
> +     vmv.v.x/vmv.s.x
> +   */

/* Here we construct a mask pattern that will later be broadcast
   to a vector register.  The maximum broadcast size for vmv.v.x/vmv.s.x
   is determined by the length of a vector element (ELEN) and not by
   XLEN so make sure we do not exceed it.  One example is -march=zve32*
   which mandates ELEN == 32 but can be combined with -march=rv64
   with XLEN == 64.  */

Regards
 Robin
  

Thanks Robin, that looks like much better than the v2, let me update it to PATCH v3.

Pan

-----Original Message-----
From: Robin Dapp <rdapp.gcc@gmail.com> 
Sent: Wednesday, June 14, 2023 4:27 PM
To: Li, Pan2 <pan2.li@intel.com>; gcc-patches@gcc.gnu.org
Cc: rdapp.gcc@gmail.com; juzhe.zhong@rivai.ai; jeffreyalaw@gmail.com; Wang, Yanzhang <yanzhang.wang@intel.com>; kito.cheng@gmail.com
Subject: Re: [PATCH v2] RISC-V: Bugfix for vec_init repeating auto vectorization in RV32

Hi Pan,

> This patch would like to fix one bug exported by RV32 test case
> multiple_rgroup_run-2.c. The mask should be restricted by elen in
> vector, and the condition between the vmv.s.x and the vmv.v.x should
> take inner_bits_size rather than constants.

exported -> exposed.

How about something like:

"When constructing a vector mask from individual elements we wrongly
assumed that we can broadcast BITS_PER_WORD (i.e. XLEN).  The maximum
is actually the vector element length (i.e. ELEN).  This patch fixes
this."?

> +  /* We restrict the limit to the elen of RVV. For example:
> +     -march=zve32*, the ELEN is 32.
> +     -march=zve64*, the ELEN is 64.
> +     The related vmv.v.x/vmv.s.x is restricted to ELEN as above, we cannot
> +     take care of case like below when ELEN=32
> +     vsetvil e64,m1
> +     vmv.v.x/vmv.s.x
> +   */

/* Here we construct a mask pattern that will later be broadcast
   to a vector register.  The maximum broadcast size for vmv.v.x/vmv.s.x
   is determined by the length of a vector element (ELEN) and not by
   XLEN so make sure we do not exceed it.  One example is -march=zve32*
   which mandates ELEN == 32 but can be combined with -march=rv64
   with XLEN == 64.  */

Regards
 Robin