* [PATCH] arm: Update strcpy.c to use UAL syntax.
@ 2017-07-19 21:02 Ian Tessier via newlib
2017-07-20 14:19 ` Corinna Vinschen
2017-07-21 10:21 ` Richard Earnshaw (lists)
0 siblings, 2 replies; 4+ messages in thread
From: Ian Tessier via newlib @ 2017-07-19 21:02 UTC (permalink / raw)
To: newlib; +Cc: Ian Tessier
With this change the arm platform can now be fully compiled with Clang.
Tested by comparing the output with GCC 4.8.2, and Clang 4.0, using a
variety of arches, big/little endianness, and arm/thumb mode to verify
the generated assembly output matches between GCC vs Clang with UAL, and
also GCC with UAL vs GCC with non-UAL, for all preprocessor code blocks.
The only difference found is an extra nop at the end of the function
when compiled with GCC using armv7-a/thumb/little-endian/-O2 compared to
Clang. The nop is not emitted when compiled in big-endian mode.
---
newlib/libc/machine/arm/strcpy.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/newlib/libc/machine/arm/strcpy.c b/newlib/libc/machine/arm/strcpy.c
index f1205b9c1..154451110 100644
--- a/newlib/libc/machine/arm/strcpy.c
+++ b/newlib/libc/machine/arm/strcpy.c
@@ -42,6 +42,7 @@ char* __attribute__((naked))
strcpy (char* dst, const char* src)
{
asm (
+ ".syntax unified\n\t"
#if !(defined(__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED) || \
(defined (__thumb__) && !defined (__thumb2__)))
#ifdef _ISA_ARM_7
@@ -127,15 +128,15 @@ strcpy (char* dst, const char* src)
#ifdef __ARMEB__
"tst r2, #0xff00\n\t"
"iteet ne\n\t"
- "strneh r2, [ip], #2\n\t"
+ "strhne r2, [ip], #2\n\t"
"lsreq r2, r2, #8\n\t"
- "streqb r2, [ip]\n\t"
+ "strbeq r2, [ip]\n\t"
"tstne r2, #0xff\n\t"
#else
"tst r2, #0xff\n\t"
"itet ne\n\t"
- "strneh r2, [ip], #2\n\t"
- "streqb r2, [ip]\n\t"
+ "strhne r2, [ip], #2\n\t"
+ "strbeq r2, [ip]\n\t"
"tstne r2, #0xff00\n\t"
#endif
"bne 5b\n\t"
@@ -162,9 +163,9 @@ strcpy (char* dst, const char* src)
"mov r3, r0\n\t"
"1:\n\t"
"ldrb r2, [r1]\n\t"
- "add r1, r1, #1\n\t"
+ "adds r1, #1\n\t"
"strb r2, [r3]\n\t"
- "add r3, r3, #1\n\t"
+ "adds r3, #1\n\t"
"cmp r2, #0\n\t"
"bne 1b\n\t"
"bx lr\n\t"
--
2.14.0.rc0.284.gd933b75aa4-goog
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm: Update strcpy.c to use UAL syntax.
2017-07-19 21:02 [PATCH] arm: Update strcpy.c to use UAL syntax Ian Tessier via newlib
@ 2017-07-20 14:19 ` Corinna Vinschen
2017-07-21 10:21 ` Richard Earnshaw (lists)
1 sibling, 0 replies; 4+ messages in thread
From: Corinna Vinschen @ 2017-07-20 14:19 UTC (permalink / raw)
To: newlib
[-- Attachment #1: Type: text/plain, Size: 2380 bytes --]
On Jul 19 14:02, Ian Tessier via newlib wrote:
> With this change the arm platform can now be fully compiled with Clang.
>
> Tested by comparing the output with GCC 4.8.2, and Clang 4.0, using a
> variety of arches, big/little endianness, and arm/thumb mode to verify
> the generated assembly output matches between GCC vs Clang with UAL, and
> also GCC with UAL vs GCC with non-UAL, for all preprocessor code blocks.
>
> The only difference found is an extra nop at the end of the function
> when compiled with GCC using armv7-a/thumb/little-endian/-O2 compared to
> Clang. The nop is not emitted when compiled in big-endian mode.
> ---
> newlib/libc/machine/arm/strcpy.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/newlib/libc/machine/arm/strcpy.c b/newlib/libc/machine/arm/strcpy.c
> index f1205b9c1..154451110 100644
> --- a/newlib/libc/machine/arm/strcpy.c
> +++ b/newlib/libc/machine/arm/strcpy.c
> @@ -42,6 +42,7 @@ char* __attribute__((naked))
> strcpy (char* dst, const char* src)
> {
> asm (
> + ".syntax unified\n\t"
> #if !(defined(__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED) || \
> (defined (__thumb__) && !defined (__thumb2__)))
> #ifdef _ISA_ARM_7
> @@ -127,15 +128,15 @@ strcpy (char* dst, const char* src)
> #ifdef __ARMEB__
> "tst r2, #0xff00\n\t"
> "iteet ne\n\t"
> - "strneh r2, [ip], #2\n\t"
> + "strhne r2, [ip], #2\n\t"
> "lsreq r2, r2, #8\n\t"
> - "streqb r2, [ip]\n\t"
> + "strbeq r2, [ip]\n\t"
> "tstne r2, #0xff\n\t"
> #else
> "tst r2, #0xff\n\t"
> "itet ne\n\t"
> - "strneh r2, [ip], #2\n\t"
> - "streqb r2, [ip]\n\t"
> + "strhne r2, [ip], #2\n\t"
> + "strbeq r2, [ip]\n\t"
> "tstne r2, #0xff00\n\t"
> #endif
> "bne 5b\n\t"
> @@ -162,9 +163,9 @@ strcpy (char* dst, const char* src)
> "mov r3, r0\n\t"
> "1:\n\t"
> "ldrb r2, [r1]\n\t"
> - "add r1, r1, #1\n\t"
> + "adds r1, #1\n\t"
> "strb r2, [r3]\n\t"
> - "add r3, r3, #1\n\t"
> + "adds r3, #1\n\t"
> "cmp r2, #0\n\t"
> "bne 1b\n\t"
> "bx lr\n\t"
> --
> 2.14.0.rc0.284.gd933b75aa4-goog
Pushed.
Thanks,
Corinna
--
Corinna Vinschen
Cygwin Maintainer
Red Hat
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm: Update strcpy.c to use UAL syntax.
2017-07-19 21:02 [PATCH] arm: Update strcpy.c to use UAL syntax Ian Tessier via newlib
2017-07-20 14:19 ` Corinna Vinschen
@ 2017-07-21 10:21 ` Richard Earnshaw (lists)
[not found] ` <CAP235ST1nYzhCDsyzE7A6NXjP2hg_sy=4bjzD_3OCXQerLYmnA@mail.gmail.com>
1 sibling, 1 reply; 4+ messages in thread
From: Richard Earnshaw (lists) @ 2017-07-21 10:21 UTC (permalink / raw)
To: Ian Tessier, newlib
[-- Attachment #1: Type: text/plain, Size: 2552 bytes --]
On 19/07/17 22:02, Ian Tessier via newlib wrote:
> With this change the arm platform can now be fully compiled with Clang.
>
> Tested by comparing the output with GCC 4.8.2, and Clang 4.0, using a
> variety of arches, big/little endianness, and arm/thumb mode to verify
> the generated assembly output matches between GCC vs Clang with UAL, and
> also GCC with UAL vs GCC with non-UAL, for all preprocessor code blocks.
>
> The only difference found is an extra nop at the end of the function
> when compiled with GCC using armv7-a/thumb/little-endian/-O2 compared to
> Clang. The nop is not emitted when compiled in big-endian mode.
> ---
> newlib/libc/machine/arm/strcpy.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/newlib/libc/machine/arm/strcpy.c b/newlib/libc/machine/arm/strcpy.c
> index f1205b9c1..154451110 100644
> --- a/newlib/libc/machine/arm/strcpy.c
> +++ b/newlib/libc/machine/arm/strcpy.c
> @@ -42,6 +42,7 @@ char* __attribute__((naked))
> strcpy (char* dst, const char* src)
> {
> asm (
> + ".syntax unified\n\t"
> #if !(defined(__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED) || \
> (defined (__thumb__) && !defined (__thumb2__)))
> #ifdef _ISA_ARM_7
> @@ -127,15 +128,15 @@ strcpy (char* dst, const char* src)
> #ifdef __ARMEB__
> "tst r2, #0xff00\n\t"
> "iteet ne\n\t"
> - "strneh r2, [ip], #2\n\t"
> + "strhne r2, [ip], #2\n\t"
> "lsreq r2, r2, #8\n\t"
> - "streqb r2, [ip]\n\t"
> + "strbeq r2, [ip]\n\t"
> "tstne r2, #0xff\n\t"
> #else
> "tst r2, #0xff\n\t"
> "itet ne\n\t"
> - "strneh r2, [ip], #2\n\t"
> - "streqb r2, [ip]\n\t"
> + "strhne r2, [ip], #2\n\t"
> + "strbeq r2, [ip]\n\t"
> "tstne r2, #0xff00\n\t"
> #endif
> "bne 5b\n\t"
> @@ -162,9 +163,9 @@ strcpy (char* dst, const char* src)
> "mov r3, r0\n\t"
> "1:\n\t"
> "ldrb r2, [r1]\n\t"
> - "add r1, r1, #1\n\t"
> + "adds r1, #1\n\t"
> "strb r2, [r3]\n\t"
> - "add r3, r3, #1\n\t"
> + "adds r3, #1\n\t"
> "cmp r2, #0\n\t"
> "bne 1b\n\t"
> "bx lr\n\t"
>
This doesn't compile on ARMv4t - you've missed the "mov r3, r0"
instruction in the final hunk.
Fixed thusly (pushed).
-------------
ARMv4t does not support mov between two low registers. Now we use
unified syntax mov instructions need converting to movs.
---
newlib/libc/machine/arm/strcpy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
[-- Attachment #2: strcpy.patch --]
[-- Type: text/x-patch, Size: 410 bytes --]
diff --git a/newlib/libc/machine/arm/strcpy.c b/newlib/libc/machine/arm/strcpy.c
index 1544511..111528e 100644
--- a/newlib/libc/machine/arm/strcpy.c
+++ b/newlib/libc/machine/arm/strcpy.c
@@ -160,7 +160,7 @@ strcpy (char* dst, const char* src)
"bne 1b\n\t"
"bx lr\n\t"
#else
- "mov r3, r0\n\t"
+ "movs r3, r0\n\t"
"1:\n\t"
"ldrb r2, [r1]\n\t"
"adds r1, #1\n\t"
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm: Update strcpy.c to use UAL syntax.
[not found] ` <CAP235ST1nYzhCDsyzE7A6NXjP2hg_sy=4bjzD_3OCXQerLYmnA@mail.gmail.com>
@ 2017-07-21 21:13 ` Ian Tessier via newlib
0 siblings, 0 replies; 4+ messages in thread
From: Ian Tessier via newlib @ 2017-07-21 21:13 UTC (permalink / raw)
To: Richard Earnshaw (lists); +Cc: newlib
Oops, I did indeed leave out armv(4|5)t. Thanks for fixing it.
Interestingly, with the non-UAL version of strcpy.c the mov
instruction gets emitted as "adds r3, r0, #0", while in UAL (both
gcc/clang) it's emitted as "movs r3, r0".
On Fri, Jul 21, 2017 at 2:11 PM, Ian Tessier <itessier@google.com> wrote:
> Oops, I did indeed leave out armv(4|5)t. Thanks for fixing it.
>
> Interestingly, with the non-UAL version of strcpy.c the mov instruction gets
> emitted as "adds r3, r0, #0", while in UAL (both gcc/clang) it's emitted as
> "movs r3, r0".
>
> On Fri, Jul 21, 2017 at 3:21 AM, Richard Earnshaw (lists)
> <Richard.Earnshaw@arm.com> wrote:
>>
>> On 19/07/17 22:02, Ian Tessier via newlib wrote:
>> > With this change the arm platform can now be fully compiled with Clang.
>> >
>> > Tested by comparing the output with GCC 4.8.2, and Clang 4.0, using a
>> > variety of arches, big/little endianness, and arm/thumb mode to verify
>> > the generated assembly output matches between GCC vs Clang with UAL, and
>> > also GCC with UAL vs GCC with non-UAL, for all preprocessor code blocks.
>> >
>> > The only difference found is an extra nop at the end of the function
>> > when compiled with GCC using armv7-a/thumb/little-endian/-O2 compared to
>> > Clang. The nop is not emitted when compiled in big-endian mode.
>> > ---
>> > newlib/libc/machine/arm/strcpy.c | 13 +++++++------
>> > 1 file changed, 7 insertions(+), 6 deletions(-)
>> >
>> > diff --git a/newlib/libc/machine/arm/strcpy.c
>> > b/newlib/libc/machine/arm/strcpy.c
>> > index f1205b9c1..154451110 100644
>> > --- a/newlib/libc/machine/arm/strcpy.c
>> > +++ b/newlib/libc/machine/arm/strcpy.c
>> > @@ -42,6 +42,7 @@ char* __attribute__((naked))
>> > strcpy (char* dst, const char* src)
>> > {
>> > asm (
>> > + ".syntax unified\n\t"
>> > #if !(defined(__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED) ||
>> > \
>> > (defined (__thumb__) && !defined (__thumb2__)))
>> > #ifdef _ISA_ARM_7
>> > @@ -127,15 +128,15 @@ strcpy (char* dst, const char* src)
>> > #ifdef __ARMEB__
>> > "tst r2, #0xff00\n\t"
>> > "iteet ne\n\t"
>> > - "strneh r2, [ip], #2\n\t"
>> > + "strhne r2, [ip], #2\n\t"
>> > "lsreq r2, r2, #8\n\t"
>> > - "streqb r2, [ip]\n\t"
>> > + "strbeq r2, [ip]\n\t"
>> > "tstne r2, #0xff\n\t"
>> > #else
>> > "tst r2, #0xff\n\t"
>> > "itet ne\n\t"
>> > - "strneh r2, [ip], #2\n\t"
>> > - "streqb r2, [ip]\n\t"
>> > + "strhne r2, [ip], #2\n\t"
>> > + "strbeq r2, [ip]\n\t"
>> > "tstne r2, #0xff00\n\t"
>> > #endif
>> > "bne 5b\n\t"
>> > @@ -162,9 +163,9 @@ strcpy (char* dst, const char* src)
>> > "mov r3, r0\n\t"
>> > "1:\n\t"
>> > "ldrb r2, [r1]\n\t"
>> > - "add r1, r1, #1\n\t"
>> > + "adds r1, #1\n\t"
>> > "strb r2, [r3]\n\t"
>> > - "add r3, r3, #1\n\t"
>> > + "adds r3, #1\n\t"
>> > "cmp r2, #0\n\t"
>> > "bne 1b\n\t"
>> > "bx lr\n\t"
>> >
>>
>> This doesn't compile on ARMv4t - you've missed the "mov r3, r0"
>> instruction in the final hunk.
>>
>> Fixed thusly (pushed).
>>
>> -------------
>>
>> ARMv4t does not support mov between two low registers. Now we use
>> unified syntax mov instructions need converting to movs.
>> ---
>> newlib/libc/machine/arm/strcpy.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-07-19 21:02 [PATCH] arm: Update strcpy.c to use UAL syntax Ian Tessier via newlib
2017-07-20 14:19 ` Corinna Vinschen
2017-07-21 10:21 ` Richard Earnshaw (lists)
[not found] ` <CAP235ST1nYzhCDsyzE7A6NXjP2hg_sy=4bjzD_3OCXQerLYmnA@mail.gmail.com>
2017-07-21 21:13 ` Ian Tessier via newlib
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