* [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization
@ 2023-12-20 6:10 Xiao Zeng
2023-12-20 6:25 ` Xiao Zeng
2023-12-20 22:48 ` Jeff Johnston
0 siblings, 2 replies; 6+ messages in thread
From: Xiao Zeng @ 2023-12-20 6:10 UTC (permalink / raw)
To: newlib; +Cc: jjohnstn, palmer, jeffreyalaw, torbjorn.svensson, Xiao Zeng
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization
2023-12-20 6:10 [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization Xiao Zeng
@ 2023-12-20 6:25 ` Xiao Zeng
2023-12-20 22:48 ` Jeff Johnston
1 sibling, 0 replies; 6+ messages in thread
From: Xiao Zeng @ 2023-12-20 6:25 UTC (permalink / raw)
To: Xiao Zeng, newlib; +Cc: Jeff Johnston, palmer, jeffreyalaw, Torbjorn SVENSSON
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization
2023-12-20 6:10 [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization Xiao Zeng
2023-12-20 6:25 ` Xiao Zeng
@ 2023-12-20 22:48 ` Jeff Johnston
2023-12-21 1:16 ` Xiao Zeng
1 sibling, 1 reply; 6+ messages in thread
From: Jeff Johnston @ 2023-12-20 22:48 UTC (permalink / raw)
To: Xiao Zeng; +Cc: newlib, palmer, jeffreyalaw, torbjorn.svensson
[-- Attachment #1: Type: text/plain, Size: 1482 bytes --]
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
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Re: [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization
2023-12-20 22:48 ` Jeff Johnston
@ 2023-12-21 1:16 ` Xiao Zeng
2023-12-21 19:05 ` Jeff Johnston
0 siblings, 1 reply; 6+ messages in thread
From: Xiao Zeng @ 2023-12-21 1:16 UTC (permalink / raw)
To: Jeff Johnston; +Cc: newlib, palmer, jeffreyalaw, Torbjorn SVENSSON
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Re: [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization
2023-12-21 1:16 ` Xiao Zeng
@ 2023-12-21 19:05 ` Jeff Johnston
2023-12-22 1:21 ` Xiao Zeng
0 siblings, 1 reply; 6+ messages in thread
From: Jeff Johnston @ 2023-12-21 19:05 UTC (permalink / raw)
To: Xiao Zeng; +Cc: newlib, palmer, jeffreyalaw, Torbjorn SVENSSON
[-- Attachment #1: Type: text/plain, Size: 5704 bytes --]
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
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Re: [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization
2023-12-21 19:05 ` Jeff Johnston
@ 2023-12-22 1:21 ` Xiao Zeng
0 siblings, 0 replies; 6+ messages in thread
From: Xiao Zeng @ 2023-12-22 1:21 UTC (permalink / raw)
To: Jeff Johnston; +Cc: newlib, palmer, jeffreyalaw, Torbjorn SVENSSON
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
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-12-22 1:22 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-12-20 6:10 [PATCH] newlib: libc: Improved the readability of strpbrk with minor optimization Xiao Zeng
2023-12-20 6:25 ` Xiao Zeng
2023-12-20 22:48 ` Jeff Johnston
2023-12-21 1:16 ` Xiao Zeng
2023-12-21 19:05 ` Jeff Johnston
2023-12-22 1:21 ` Xiao Zeng
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