[gcc r14-5811] RISC-V: Disable BSWAP optimization for NUNITS < 4

[Pan Li <panli@gcc.gnu.org>]

https://gcc.gnu.org/g:af7a422da457aa13df8eb1feb601dffafb76ed7c

commit r14-5811-gaf7a422da457aa13df8eb1feb601dffafb76ed7c
Author: Juzhe-Zhong <juzhe.zhong@rivai.ai>
Date:   Fri Nov 24 13:04:18 2023 +0800

    RISC-V: Disable BSWAP optimization for NUNITS < 4
    
    When fixing bugs, I notice there is a piece odd codes look incorrect.
    which probably make codegen worse.
    
    #include <stdint.h>
    
    typedef int8_t vnx2qi __attribute__ ((vector_size (2)));
    
    #define MASK_2(X, Y) (Y) - 1 - (X), (Y) - 2 - (X)
    
    #define PERMUTE(TYPE, NUNITS)                                                  \
      __attribute__ ((noipa)) void permute_##TYPE (TYPE values1, TYPE values2,     \
                                                   TYPE *out)                      \
      {                                                                            \
        TYPE v                                                                     \
          = __builtin_shufflevector (values1, values2, MASK_##NUNITS (0, NUNITS)); \
        *(TYPE *) out = v;                                                         \
      }
    
    #define TEST_ALL(T)                                                            \
      T (vnx2qi, 2)
    
    TEST_ALL (PERMUTE)
    
    Before this patch:
    
            vsetivli        zero,2,e8,mf8,ta,ma
            vle8.v  v1,0(a0)
            vsetivli        zero,1,e16,mf4,ta,ma
            vsrl.vi v2,v1,8
            vsll.vi v1,v1,8
            vor.vv  v1,v2,v1
            vsetivli        zero,2,e8,mf8,ta,ma
            vse8.v  v1,0(a2)
            ret
    
    After this patch:
    
            vsetivli        zero,2,e8,mf8,ta,ma
            vle8.v  v3,0(a0)
            vid.v   v1
            vrsub.vi        v1,v1,1
            vrgather.vv     v2,v3,v1
            vse8.v  v2,0(a2)
            ret
    
    Committed as it is very obvious if during code review.
    
    gcc/ChangeLog:
    
            * config/riscv/riscv-v.cc (shuffle_bswap_pattern): Disable for NUNIT < 4.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c: Adapt test.
            * gcc.target/riscv/rvv/autovec/vls/perm-4.c: Ditto.

Diff:
---
 gcc/config/riscv/riscv-v.cc                                   | 5 +++++
 gcc/testsuite/gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c | 4 ++--
 gcc/testsuite/gcc.target/riscv/rvv/autovec/vls/perm-4.c       | 4 ++--
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/gcc/config/riscv/riscv-v.cc b/gcc/config/riscv/riscv-v.cc
index 72b96d8339d..acf40973322 100644
--- a/gcc/config/riscv/riscv-v.cc
+++ b/gcc/config/riscv/riscv-v.cc
@@ -3201,6 +3201,11 @@ shuffle_bswap_pattern (struct expand_vec_perm_d *d)
     if (!d->perm.series_p (i, step, diff - i, step))
       return false;
 
+  /* Disable when nunits < 4 since the later generic approach
+     is more profitable on BSWAP.  */
+  if (!known_gt (GET_MODE_NUNITS (d->vmode), 2))
+    return false;
+
   if (d->testing_p)
     return true;
 
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c
index b235ec727b1..7ab31043547 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls-vlmax/perm-4.c
@@ -55,7 +55,7 @@
 
 TEST_ALL (PERMUTE)
 
-/* { dg-final { scan-assembler-times {vrgather\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 18 } } */
+/* { dg-final { scan-assembler-times {vrgather\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 19 } } */
 /* { dg-final { scan-assembler-times {vrgatherei16\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 12 } } */
-/* { dg-final { scan-assembler-times {vrsub\.vi} 23 } } */
+/* { dg-final { scan-assembler-times {vrsub\.vi} 24 } } */
 /* { dg-final { scan-assembler-times {vrsub\.vx} 7 } } */
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls/perm-4.c b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls/perm-4.c
index d2d49388a39..4d6862cf1c0 100644
--- a/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls/perm-4.c
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/vls/perm-4.c
@@ -3,7 +3,7 @@
 
 #include "../vls-vlmax/perm-4.c"
 
-/* { dg-final { scan-assembler-times {vrgather\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 18 } } */
+/* { dg-final { scan-assembler-times {vrgather\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 19 } } */
 /* { dg-final { scan-assembler-times {vrgatherei16\.vv\tv[0-9]+,\s*v[0-9]+,\s*v[0-9]+} 12 } } */
-/* { dg-final { scan-assembler-times {vrsub\.vi} 23 } } */
+/* { dg-final { scan-assembler-times {vrsub\.vi} 24 } } */
 /* { dg-final { scan-assembler-times {vrsub\.vx} 7 } } */