newlib: libc: Improved the readability of strpbrk with minor optimization

Message ID 20231220061054.35685-1-zengxiao@eswincomputing.com
State New
Headers
Series newlib: libc: Improved the readability of strpbrk with minor optimization |

Commit Message

Xiao Zeng Dec. 20, 2023, 6:10 a.m. UTC
  Signed-off-by: Xiao Zeng <zengxiao@eswincomputing.com>
---
 newlib/libc/string/strpbrk.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)
  

Comments

Xiao Zeng Dec. 20, 2023, 6:25 a.m. UTC | #1
As mentioned in [PATCH] newlib: libc: Improved the readability of strcspn with minor optimization: <https://sourceware.org/pipermail/newlib/2023/020766.html>

This patch did the same thing and passed the testcases.

Similarly, provide a comparison of risc-v assembly:

no-patch:
---------------------------------------------------------
libc_a-strpbrk.o:     file format elf64-littleriscv


Disassembly of section .text:

0000000000000000 <strpbrk>:
   0:   00054683                lbu     a3,0(a0)

0000000000000004 <.LVL1>:
   4:   06068463                beqz    a3,6c <.L8>
   8:   0005c603                lbu     a2,0(a1)

000000000000000c <.LVL2>:
   c:   02060e63                beqz    a2,48 <.L14>

0000000000000010 <.L6>:
  10:   00058713                mv      a4,a1
  14:   00060793                mv      a5,a2

0000000000000018 <.L5>:
  18:   00f68e63                beq     a3,a5,34 <.L4>
  1c:   00174783                lbu     a5,1(a4)
  20:   00170713                addi    a4,a4,1

0000000000000024 <.LVL4>:
  24:   fe079ae3                bnez    a5,18 <.L5>
  28:   00154683                lbu     a3,1(a0)
  2c:   00150513                addi    a0,a0,1

0000000000000030 <.LVL5>:
  30:   fe0690e3                bnez    a3,10 <.L6>

0000000000000034 <.L4>:
  34:   00074783                lbu     a5,0(a4)
  38:   00f037b3                snez    a5,a5
  3c:   40f007b3                neg     a5,a5
  40:   00f57533                and     a0,a0,a5
  44:   00008067                ret

0000000000000048 <.L14>:
  48:   00154683                lbu     a3,1(a0)
  4c:   00150513                addi    a0,a0,1

0000000000000050 <.LVL8>:
  50:   fe069ce3                bnez    a3,48 <.L14>
  54:   00058713                mv      a4,a1
  58:   00074783                lbu     a5,0(a4)
  5c:   00f037b3                snez    a5,a5
  60:   40f007b3                neg     a5,a5
  64:   00f57533                and     a0,a0,a5

0000000000000068 <.LVL9>:
  68:   00008067                ret

000000000000006c <.L8>:
  6c:   00000513                li      a0,0

0000000000000070 <.LVL11>:
  70:   00008067                ret
---------------------------------------------------------

patch
---------------------------------------------------------
libc_a-strpbrk.o:     file format elf64-littleriscv


Disassembly of section .text:

0000000000000000 <strpbrk>:
   0:   00054683                lbu     a3,0(a0)

0000000000000004 <.LVL1>:
   4:   04068063                beqz    a3,44 <.L10>
   8:   0005c603                lbu     a2,0(a1)
   c:   04060063                beqz    a2,4c <.L14>

0000000000000010 <.L5>:
  10:   00058793                mv      a5,a1
  14:   00060713                mv      a4,a2
  18:   00c0006f                j       24 <.L4>

000000000000001c <.L17>:
  1c:   0007c703                lbu     a4,0(a5)
  20:   00070863                beqz    a4,30 <.L16>

0000000000000024 <.L4>:
  24:   00178793                addi    a5,a5,1

0000000000000028 <.LVL5>:
  28:   fee69ae3                bne     a3,a4,1c <.L17>

000000000000002c <.L1>:
  2c:   00008067                ret

0000000000000030 <.L16>:
  30:   00154683                lbu     a3,1(a0)
  34:   00150513                addi    a0,a0,1

0000000000000038 <.LVL8>:
  38:   fc069ce3                bnez    a3,10 <.L5>

000000000000003c <.L6>:
  3c:   0007c783                lbu     a5,0(a5)

0000000000000040 <.LVL9>:
  40:   fe0796e3                bnez    a5,2c <.L1>

0000000000000044 <.L10>:
  44:   00000513                li      a0,0

0000000000000048 <.LVL11>:
  48:   00008067                ret

000000000000004c <.L14>:
  4c:   00154683                lbu     a3,1(a0)
  50:   00150513                addi    a0,a0,1
  54:   fe069ce3                bnez    a3,4c <.L14>
  58:   00058793                mv      a5,a1
  5c:   fe1ff06f                j       3c <.L6>
---------------------------------------------------------
After careful comparison, it was found that there are fewer assembly
instructions after the patch.

2023-12-20 14:10  Xiao Zeng <zengxiao@eswincomputing.com> wrote:
>
 
>Signed-off-by: Xiao Zeng <zengxiao@eswincomputing.com>
>---
> newlib/libc/string/strpbrk.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
>diff --git a/newlib/libc/string/strpbrk.c b/newlib/libc/string/strpbrk.c
>index 774db1e6d..95e89c20c 100644
>--- a/newlib/libc/string/strpbrk.c
>+++ b/newlib/libc/string/strpbrk.c
>@@ -37,15 +37,14 @@ strpbrk (const char *s1,
>       for (c = s2; *c; c++)
> {
>   if (*s1 == *c)
>-	    break;
>+	    goto end;
> }
>-      if (*c)
>-	break;
>       s1++;
>     }
>
>   if (*c == '\0')
>     s1 = NULL;
>
>+end:
>   return (char *) s1;
> }
>--
>2.17.1
 
Thanks
Xiao Zeng
  
Jeff Johnston Dec. 20, 2023, 10:48 p.m. UTC | #2
Unless I am missing something, I think the code could be made even simpler
to return the pointer when found and return NULL otherwise.

index 774db1e..d984745 100644
--- a/newlib/libc/string/strpbrk.c
+++ b/newlib/libc/string/strpbrk.c
@@ -29,23 +29,16 @@ strpbrk (const char *s1,
        const char *s2)
 {
   const char *c = s2;
-  if (!*s1)
-    return (char *) NULL;

   while (*s1)
     {
       for (c = s2; *c; c++)
        {
          if (*s1 == *c)
-           break;
+           return (char *) s1;
        }
-      if (*c)
-       break;
       s1++;
     }

-  if (*c == '\0')
-    s1 = NULL;
-
-  return (char *) s1;
+  return (char *) NULL;
 }

On Wed, Dec 20, 2023 at 1:12 AM Xiao Zeng <zengxiao@eswincomputing.com>
wrote:

> Signed-off-by: Xiao Zeng <zengxiao@eswincomputing.com>
> ---
>  newlib/libc/string/strpbrk.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/newlib/libc/string/strpbrk.c b/newlib/libc/string/strpbrk.c
> index 774db1e6d..95e89c20c 100644
> --- a/newlib/libc/string/strpbrk.c
> +++ b/newlib/libc/string/strpbrk.c
> @@ -37,15 +37,14 @@ strpbrk (const char *s1,
>        for (c = s2; *c; c++)
>         {
>           if (*s1 == *c)
> -           break;
> +           goto end;
>         }
> -      if (*c)
> -       break;
>        s1++;
>      }
>
>    if (*c == '\0')
>      s1 = NULL;
>
> +end:
>    return (char *) s1;
>  }
> --
> 2.17.1
>
>
  
Xiao Zeng Dec. 21, 2023, 1:16 a.m. UTC | #3
2023-12-21 06:48  Jeff Johnston <jjohnstn@redhat.com> wrote:
>
 
>Unless I am missing something, I think the code could be made even simpler
>to return the pointer when found and return NULL otherwise. 
Yes, you have found a more efficient method.
After my testing, fewer assembly instructions were generated. This is really exciting.

Xiao's patch:
---------------------------------------------------------
libc_a-strpbrk.o:     file format elf64-littleriscv


Disassembly of section .text:

0000000000000000 <strpbrk>:
   0:   00054683                lbu     a3,0(a0)

0000000000000004 <.LVL1>:
   4:   04068063                beqz    a3,44 <.L10>
   8:   0005c603                lbu     a2,0(a1)
   c:   04060063                beqz    a2,4c <.L14>

0000000000000010 <.L5>:
  10:   00058793                mv      a5,a1
  14:   00060713                mv      a4,a2
  18:   00c0006f                j       24 <.L4>

000000000000001c <.L17>:
  1c:   0007c703                lbu     a4,0(a5)
  20:   00070863                beqz    a4,30 <.L16>

0000000000000024 <.L4>:
  24:   00178793                addi    a5,a5,1

0000000000000028 <.LVL5>:
  28:   fee69ae3                bne     a3,a4,1c <.L17>

000000000000002c <.L1>:
  2c:   00008067                ret

0000000000000030 <.L16>:
  30:   00154683                lbu     a3,1(a0)
  34:   00150513                addi    a0,a0,1

0000000000000038 <.LVL8>:
  38:   fc069ce3                bnez    a3,10 <.L5>

000000000000003c <.L6>:
  3c:   0007c783                lbu     a5,0(a5)

0000000000000040 <.LVL9>:
  40:   fe0796e3                bnez    a5,2c <.L1>

0000000000000044 <.L10>:
  44:   00000513                li      a0,0

0000000000000048 <.LVL11>:
  48:   00008067                ret

000000000000004c <.L14>:
  4c:   00154683                lbu     a3,1(a0)
  50:   00150513                addi    a0,a0,1
  54:   fe069ce3                bnez    a3,4c <.L14>
  58:   00058793                mv      a5,a1
  5c:   fe1ff06f                j       3c <.L6>
---------------------------------------------------------

Jeff's patch
---------------------------------------------------------
libc_a-strpbrk.o:     file format elf64-littleriscv


Disassembly of section .text:

0000000000000000 <strpbrk>:
   0:   00054683                lbu     a3,0(a0)
   4:   02068c63                beqz    a3,3c <.L8>
   8:   0005c603                lbu     a2,0(a1)
   c:   02060c63                beqz    a2,44 <.L12>

0000000000000010 <.L5>:
  10:   00058793                mv      a5,a1
  14:   00060713                mv      a4,a2
  18:   00c0006f                j       24 <.L4>

000000000000001c <.L15>:
  1c:   0007c703                lbu     a4,0(a5)
  20:   00070863                beqz    a4,30 <.L14>

0000000000000024 <.L4>:
  24:   00178793                addi    a5,a5,1

0000000000000028 <.LVL4>:
  28:   fed71ae3                bne     a4,a3,1c <.L15>
  2c:   00008067                ret

0000000000000030 <.L14>:
  30:   00154683                lbu     a3,1(a0)
  34:   00150513                addi    a0,a0,1

0000000000000038 <.LVL6>:
  38:   fc069ce3                bnez    a3,10 <.L5>

000000000000003c <.L8>:
  3c:   00000513                li      a0,0

0000000000000040 <.LVL7>:
  40:   00008067                ret

0000000000000044 <.L12>:
  44:   00154683                lbu     a3,1(a0)
  48:   00150513                addi    a0,a0,1
  4c:   fe069ce3                bnez    a3,44 <.L12>
  50:   fedff06f                j       3c <.L8>
---------------------------------------------------------
After careful comparison, it was found that there are fewer assembly
instructions after the Jeff's patch.

>
>index 774db1e..d984745 100644
>--- a/newlib/libc/string/strpbrk.c
>+++ b/newlib/libc/string/strpbrk.c
>@@ -29,23 +29,16 @@ strpbrk (const char *s1,
>        const char *s2)
> {
>   const char *c = s2;
>-  if (!*s1)
>-    return (char *) NULL;
>
>   while (*s1)
>     {
>       for (c = s2; *c; c++)
>        {
>          if (*s1 == *c)
>-           break;
>+           return (char *) s1;
>        }
>-      if (*c)
>-       break;
>       s1++;
>     }
>
>-  if (*c == '\0')
>-    s1 = NULL;
>-
>-  return (char *) s1;
>+  return (char *) NULL;
> }
>
>On Wed, Dec 20, 2023 at 1:12 AM Xiao Zeng <zengxiao@eswincomputing.com>
>wrote:
>
>> Signed-off-by: Xiao Zeng <zengxiao@eswincomputing.com>
>> ---
>>  newlib/libc/string/strpbrk.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/newlib/libc/string/strpbrk.c b/newlib/libc/string/strpbrk.c
>> index 774db1e6d..95e89c20c 100644
>> --- a/newlib/libc/string/strpbrk.c
>> +++ b/newlib/libc/string/strpbrk.c
>> @@ -37,15 +37,14 @@ strpbrk (const char *s1,
>>        for (c = s2; *c; c++)
>>         {
>>           if (*s1 == *c)
>> -           break;
>> +           goto end;
>>         }
>> -      if (*c)
>> -       break;
>>        s1++;
>>      }
>>
>>    if (*c == '\0')
>>      s1 = NULL;
>>
>> +end:
>>    return (char *) s1;
>>  }
>> --
>> 2.17.1
>>
>>
 
Thanks
Xiao Zeng
  
Jeff Johnston Dec. 21, 2023, 7:05 p.m. UTC | #4
Patch merged.  Thanks.

-- Jeff J.

On Wed, Dec 20, 2023 at 8:16 PM Xiao Zeng <zengxiao@eswincomputing.com>
wrote:

> 2023-12-21 06:48  Jeff Johnston <jjohnstn@redhat.com> wrote:
> >
>
> >Unless I am missing something, I think the code could be made even simpler
> >to return the pointer when found and return NULL otherwise.
> Yes, you have found a more efficient method.
> After my testing, fewer assembly instructions were generated. This is
> really exciting.
>
> Xiao's patch:
> ---------------------------------------------------------
> libc_a-strpbrk.o:     file format elf64-littleriscv
>
>
> Disassembly of section .text:
>
> 0000000000000000 <strpbrk>:
>    0:   00054683                lbu     a3,0(a0)
>
> 0000000000000004 <.LVL1>:
>    4:   04068063                beqz    a3,44 <.L10>
>    8:   0005c603                lbu     a2,0(a1)
>    c:   04060063                beqz    a2,4c <.L14>
>
> 0000000000000010 <.L5>:
>   10:   00058793                mv      a5,a1
>   14:   00060713                mv      a4,a2
>   18:   00c0006f                j       24 <.L4>
>
> 000000000000001c <.L17>:
>   1c:   0007c703                lbu     a4,0(a5)
>   20:   00070863                beqz    a4,30 <.L16>
>
> 0000000000000024 <.L4>:
>   24:   00178793                addi    a5,a5,1
>
> 0000000000000028 <.LVL5>:
>   28:   fee69ae3                bne     a3,a4,1c <.L17>
>
> 000000000000002c <.L1>:
>   2c:   00008067                ret
>
> 0000000000000030 <.L16>:
>   30:   00154683                lbu     a3,1(a0)
>   34:   00150513                addi    a0,a0,1
>
> 0000000000000038 <.LVL8>:
>   38:   fc069ce3                bnez    a3,10 <.L5>
>
> 000000000000003c <.L6>:
>   3c:   0007c783                lbu     a5,0(a5)
>
> 0000000000000040 <.LVL9>:
>   40:   fe0796e3                bnez    a5,2c <.L1>
>
> 0000000000000044 <.L10>:
>   44:   00000513                li      a0,0
>
> 0000000000000048 <.LVL11>:
>   48:   00008067                ret
>
> 000000000000004c <.L14>:
>   4c:   00154683                lbu     a3,1(a0)
>   50:   00150513                addi    a0,a0,1
>   54:   fe069ce3                bnez    a3,4c <.L14>
>   58:   00058793                mv      a5,a1
>   5c:   fe1ff06f                j       3c <.L6>
> ---------------------------------------------------------
>
> Jeff's patch
> ---------------------------------------------------------
> libc_a-strpbrk.o:     file format elf64-littleriscv
>
>
> Disassembly of section .text:
>
> 0000000000000000 <strpbrk>:
>    0:   00054683                lbu     a3,0(a0)
>    4:   02068c63                beqz    a3,3c <.L8>
>    8:   0005c603                lbu     a2,0(a1)
>    c:   02060c63                beqz    a2,44 <.L12>
>
> 0000000000000010 <.L5>:
>   10:   00058793                mv      a5,a1
>   14:   00060713                mv      a4,a2
>   18:   00c0006f                j       24 <.L4>
>
> 000000000000001c <.L15>:
>   1c:   0007c703                lbu     a4,0(a5)
>   20:   00070863                beqz    a4,30 <.L14>
>
> 0000000000000024 <.L4>:
>   24:   00178793                addi    a5,a5,1
>
> 0000000000000028 <.LVL4>:
>   28:   fed71ae3                bne     a4,a3,1c <.L15>
>   2c:   00008067                ret
>
> 0000000000000030 <.L14>:
>   30:   00154683                lbu     a3,1(a0)
>   34:   00150513                addi    a0,a0,1
>
> 0000000000000038 <.LVL6>:
>   38:   fc069ce3                bnez    a3,10 <.L5>
>
> 000000000000003c <.L8>:
>   3c:   00000513                li      a0,0
>
> 0000000000000040 <.LVL7>:
>   40:   00008067                ret
>
> 0000000000000044 <.L12>:
>   44:   00154683                lbu     a3,1(a0)
>   48:   00150513                addi    a0,a0,1
>   4c:   fe069ce3                bnez    a3,44 <.L12>
>   50:   fedff06f                j       3c <.L8>
> ---------------------------------------------------------
> After careful comparison, it was found that there are fewer assembly
> instructions after the Jeff's patch.
>
> >
> >index 774db1e..d984745 100644
> >--- a/newlib/libc/string/strpbrk.c
> >+++ b/newlib/libc/string/strpbrk.c
> >@@ -29,23 +29,16 @@ strpbrk (const char *s1,
> >        const char *s2)
> > {
> >   const char *c = s2;
> >-  if (!*s1)
> >-    return (char *) NULL;
> >
> >   while (*s1)
> >     {
> >       for (c = s2; *c; c++)
> >        {
> >          if (*s1 == *c)
> >-           break;
> >+           return (char *) s1;
> >        }
> >-      if (*c)
> >-       break;
> >       s1++;
> >     }
> >
> >-  if (*c == '\0')
> >-    s1 = NULL;
> >-
> >-  return (char *) s1;
> >+  return (char *) NULL;
> > }
> >
> >On Wed, Dec 20, 2023 at 1:12 AM Xiao Zeng <zengxiao@eswincomputing.com>
> >wrote:
> >
> >> Signed-off-by: Xiao Zeng <zengxiao@eswincomputing.com>
> >> ---
> >>  newlib/libc/string/strpbrk.c | 5 ++---
> >>  1 file changed, 2 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/newlib/libc/string/strpbrk.c b/newlib/libc/string/strpbrk.c
> >> index 774db1e6d..95e89c20c 100644
> >> --- a/newlib/libc/string/strpbrk.c
> >> +++ b/newlib/libc/string/strpbrk.c
> >> @@ -37,15 +37,14 @@ strpbrk (const char *s1,
> >>        for (c = s2; *c; c++)
> >>         {
> >>           if (*s1 == *c)
> >> -           break;
> >> +           goto end;
> >>         }
> >> -      if (*c)
> >> -       break;
> >>        s1++;
> >>      }
> >>
> >>    if (*c == '\0')
> >>      s1 = NULL;
> >>
> >> +end:
> >>    return (char *) s1;
> >>  }
> >> --
> >> 2.17.1
> >>
> >>
>
> Thanks
> Xiao Zeng
>
>
  
Xiao Zeng Dec. 22, 2023, 1:21 a.m. UTC | #5
2023-12-22 03:05  Jeff Johnston <jjohnstn@redhat.com> wrote:
>
 
>Patch merged.  Thanks. 
Thank you, Jeff.
Perhaps the two emails are too similar, I would like to remind you that there is a similar optimization on
<https://sourceware.org/pipermail/newlib/2023/020771.html>.

>
>-- Jeff J.
>
>On Wed, Dec 20, 2023 at 8:16 PM Xiao Zeng <zengxiao@eswincomputing.com>
>wrote:
>
>> 2023-12-21 06:48  Jeff Johnston <jjohnstn@redhat.com> wrote:
>> >
>>
>> >Unless I am missing something, I think the code could be made even simpler
>> >to return the pointer when found and return NULL otherwise.
>> Yes, you have found a more efficient method.
>> After my testing, fewer assembly instructions were generated. This is
>> really exciting.
>>
>> Xiao's patch:
>> ---------------------------------------------------------
>> libc_a-strpbrk.o:     file format elf64-littleriscv
>>
>>
>> Disassembly of section .text:
>>
>> 0000000000000000 <strpbrk>:
>>    0:   00054683                lbu     a3,0(a0)
>>
>> 0000000000000004 <.LVL1>:
>>    4:   04068063                beqz    a3,44 <.L10>
>>    8:   0005c603                lbu     a2,0(a1)
>>    c:   04060063                beqz    a2,4c <.L14>
>>
>> 0000000000000010 <.L5>:
>>   10:   00058793                mv      a5,a1
>>   14:   00060713                mv      a4,a2
>>   18:   00c0006f                j       24 <.L4>
>>
>> 000000000000001c <.L17>:
>>   1c:   0007c703                lbu     a4,0(a5)
>>   20:   00070863                beqz    a4,30 <.L16>
>>
>> 0000000000000024 <.L4>:
>>   24:   00178793                addi    a5,a5,1
>>
>> 0000000000000028 <.LVL5>:
>>   28:   fee69ae3                bne     a3,a4,1c <.L17>
>>
>> 000000000000002c <.L1>:
>>   2c:   00008067                ret
>>
>> 0000000000000030 <.L16>:
>>   30:   00154683                lbu     a3,1(a0)
>>   34:   00150513                addi    a0,a0,1
>>
>> 0000000000000038 <.LVL8>:
>>   38:   fc069ce3                bnez    a3,10 <.L5>
>>
>> 000000000000003c <.L6>:
>>   3c:   0007c783                lbu     a5,0(a5)
>>
>> 0000000000000040 <.LVL9>:
>>   40:   fe0796e3                bnez    a5,2c <.L1>
>>
>> 0000000000000044 <.L10>:
>>   44:   00000513                li      a0,0
>>
>> 0000000000000048 <.LVL11>:
>>   48:   00008067                ret
>>
>> 000000000000004c <.L14>:
>>   4c:   00154683                lbu     a3,1(a0)
>>   50:   00150513                addi    a0,a0,1
>>   54:   fe069ce3                bnez    a3,4c <.L14>
>>   58:   00058793                mv      a5,a1
>>   5c:   fe1ff06f                j       3c <.L6>
>> ---------------------------------------------------------
>>
>> Jeff's patch
>> ---------------------------------------------------------
>> libc_a-strpbrk.o:     file format elf64-littleriscv
>>
>>
>> Disassembly of section .text:
>>
>> 0000000000000000 <strpbrk>:
>>    0:   00054683                lbu     a3,0(a0)
>>    4:   02068c63                beqz    a3,3c <.L8>
>>    8:   0005c603                lbu     a2,0(a1)
>>    c:   02060c63                beqz    a2,44 <.L12>
>>
>> 0000000000000010 <.L5>:
>>   10:   00058793                mv      a5,a1
>>   14:   00060713                mv      a4,a2
>>   18:   00c0006f                j       24 <.L4>
>>
>> 000000000000001c <.L15>:
>>   1c:   0007c703                lbu     a4,0(a5)
>>   20:   00070863                beqz    a4,30 <.L14>
>>
>> 0000000000000024 <.L4>:
>>   24:   00178793                addi    a5,a5,1
>>
>> 0000000000000028 <.LVL4>:
>>   28:   fed71ae3                bne     a4,a3,1c <.L15>
>>   2c:   00008067                ret
>>
>> 0000000000000030 <.L14>:
>>   30:   00154683                lbu     a3,1(a0)
>>   34:   00150513                addi    a0,a0,1
>>
>> 0000000000000038 <.LVL6>:
>>   38:   fc069ce3                bnez    a3,10 <.L5>
>>
>> 000000000000003c <.L8>:
>>   3c:   00000513                li      a0,0
>>
>> 0000000000000040 <.LVL7>:
>>   40:   00008067                ret
>>
>> 0000000000000044 <.L12>:
>>   44:   00154683                lbu     a3,1(a0)
>>   48:   00150513                addi    a0,a0,1
>>   4c:   fe069ce3                bnez    a3,44 <.L12>
>>   50:   fedff06f                j       3c <.L8>
>> ---------------------------------------------------------
>> After careful comparison, it was found that there are fewer assembly
>> instructions after the Jeff's patch.
>>
>> >
>> >index 774db1e..d984745 100644
>> >--- a/newlib/libc/string/strpbrk.c
>> >+++ b/newlib/libc/string/strpbrk.c
>> >@@ -29,23 +29,16 @@ strpbrk (const char *s1,
>> >        const char *s2)
>> > {
>> >   const char *c = s2;
>> >-  if (!*s1)
>> >-    return (char *) NULL;
>> >
>> >   while (*s1)
>> >     {
>> >       for (c = s2; *c; c++)
>> >        {
>> >          if (*s1 == *c)
>> >-           break;
>> >+           return (char *) s1;
>> >        }
>> >-      if (*c)
>> >-       break;
>> >       s1++;
>> >     }
>> >
>> >-  if (*c == '\0')
>> >-    s1 = NULL;
>> >-
>> >-  return (char *) s1;
>> >+  return (char *) NULL;
>> > }
>> >
>> >On Wed, Dec 20, 2023 at 1:12 AM Xiao Zeng <zengxiao@eswincomputing.com>
>> >wrote:
>> >
>> >> Signed-off-by: Xiao Zeng <zengxiao@eswincomputing.com>
>> >> ---
>> >>  newlib/libc/string/strpbrk.c | 5 ++---
>> >>  1 file changed, 2 insertions(+), 3 deletions(-)
>> >>
>> >> diff --git a/newlib/libc/string/strpbrk.c b/newlib/libc/string/strpbrk.c
>> >> index 774db1e6d..95e89c20c 100644
>> >> --- a/newlib/libc/string/strpbrk.c
>> >> +++ b/newlib/libc/string/strpbrk.c
>> >> @@ -37,15 +37,14 @@ strpbrk (const char *s1,
>> >>        for (c = s2; *c; c++)
>> >>         {
>> >>           if (*s1 == *c)
>> >> -           break;
>> >> +           goto end;
>> >>         }
>> >> -      if (*c)
>> >> -       break;
>> >>        s1++;
>> >>      }
>> >>
>> >>    if (*c == '\0')
>> >>      s1 = NULL;
>> >>
>> >> +end:
>> >>    return (char *) s1;
>> >>  }
>> >> --
>> >> 2.17.1
>> >>
>> >>
>>
>> Thanks
>> Xiao Zeng
>>
>>
 
Thanks
Xiao Zeng
  

Patch

diff --git a/newlib/libc/string/strpbrk.c b/newlib/libc/string/strpbrk.c
index 774db1e6d..95e89c20c 100644
--- a/newlib/libc/string/strpbrk.c
+++ b/newlib/libc/string/strpbrk.c
@@ -37,15 +37,14 @@  strpbrk (const char *s1,
       for (c = s2; *c; c++)
 	{
 	  if (*s1 == *c)
-	    break;
+	    goto end;
 	}
-      if (*c)
-	break;
       s1++;
     }
 
   if (*c == '\0')
     s1 = NULL;
 
+end:
   return (char *) s1;
 }