[PATCH v1] kselftest/arm64: Use preferred form for predicate load/stores

[PATCH v1] kselftest/arm64: Use preferred form for predicate load/stores

[Mark Brown]

The preferred form of the str/ldr for predicate registers with an immediate
of zero is to omit the zero, and the clang built in assembler rejects the
zero immediate. Drop the immediate.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 tools/testing/selftests/arm64/abi/syscall-abi-asm.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/arm64/abi/syscall-abi-asm.S b/tools/testing/selftests/arm64/abi/syscall-abi-asm.S
index b523c21c2278..acd5e9f3bc0b 100644
--- a/tools/testing/selftests/arm64/abi/syscall-abi-asm.S
+++ b/tools/testing/selftests/arm64/abi/syscall-abi-asm.S
@@ -153,7 +153,7 @@ do_syscall:
 	// Only set a non-zero FFR, test patterns must be zero since the
 	// syscall should clear it - this lets us handle FA64.
 	ldr	x2, =ffr_in
-	ldr	p0, [x2, #0]
+	ldr	p0, [x2]
 	ldr	x2, [x2, #0]
 	cbz	x2, 2f
 	wrffr	p0.b
@@ -298,7 +298,7 @@ do_syscall:
 	cbz	x2, 1f
 	ldr	x2, =ffr_out
 	rdffr	p0.b
-	str	p0, [x2, #0]
+	str	p0, [x2]
 1:
 
 	// Restore callee saved registers x19-x30

base-commit: 30a0b95b1335e12efef89dd78518ed3e4a71a763
-- 
2.30.2


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v1] kselftest/arm64: Use preferred form for predicate load/stores

[Mark Rutland]

On Thu, Nov 17, 2022 at 11:41:30AM +0000, Mark Brown wrote:
> The preferred form of the str/ldr for predicate registers with an immediate
> of zero is to omit the zero, and the clang built in assembler rejects the
> zero immediate. Drop the immediate.

Rejecting that outright seems like a bug in clang, given there are legitimate
reasons to write code that way (e.g. using asm-offsets style definitions); has
that been reported so that it can be fixed?

Regardless, the patch itself looks fine, and I don't mean to block this as-is!

Thanks,
Mark.

> 
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>  tools/testing/selftests/arm64/abi/syscall-abi-asm.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/arm64/abi/syscall-abi-asm.S b/tools/testing/selftests/arm64/abi/syscall-abi-asm.S
> index b523c21c2278..acd5e9f3bc0b 100644
> --- a/tools/testing/selftests/arm64/abi/syscall-abi-asm.S
> +++ b/tools/testing/selftests/arm64/abi/syscall-abi-asm.S
> @@ -153,7 +153,7 @@ do_syscall:
>  	// Only set a non-zero FFR, test patterns must be zero since the
>  	// syscall should clear it - this lets us handle FA64.
>  	ldr	x2, =ffr_in
> -	ldr	p0, [x2, #0]
> +	ldr	p0, [x2]
>  	ldr	x2, [x2, #0]
>  	cbz	x2, 2f
>  	wrffr	p0.b
> @@ -298,7 +298,7 @@ do_syscall:
>  	cbz	x2, 1f
>  	ldr	x2, =ffr_out
>  	rdffr	p0.b
> -	str	p0, [x2, #0]
> +	str	p0, [x2]
>  1:
>  
>  	// Restore callee saved registers x19-x30
> 
> base-commit: 30a0b95b1335e12efef89dd78518ed3e4a71a763
> -- 
> 2.30.2
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v1] kselftest/arm64: Use preferred form for predicate load/stores

[Mark Brown]

[-- Attachment #1.1: Type: text/plain, Size: 567 bytes --]

On Thu, Nov 17, 2022 at 11:52:22AM +0000, Mark Rutland wrote:
> On Thu, Nov 17, 2022 at 11:41:30AM +0000, Mark Brown wrote:

> > The preferred form of the str/ldr for predicate registers with an immediate
> > of zero is to omit the zero, and the clang built in assembler rejects the
> > zero immediate. Drop the immediate.

> Rejecting that outright seems like a bug in clang, given there are legitimate
> reasons to write code that way (e.g. using asm-offsets style definitions); has
> that been reported so that it can be fixed?

I believe it's been reported, yes.

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[-- Attachment #2: Type: text/plain, Size: 176 bytes --]

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v1] kselftest/arm64: Use preferred form for predicate load/stores

[Will Deacon]

On Thu, 17 Nov 2022 11:41:30 +0000, Mark Brown wrote:
> The preferred form of the str/ldr for predicate registers with an immediate
> of zero is to omit the zero, and the clang built in assembler rejects the
> zero immediate. Drop the immediate.
> 
> 

Applied to arm64 (for-next/selftests), thanks!

[1/1] kselftest/arm64: Use preferred form for predicate load/stores
      https://git.kernel.org/arm64/c/284d2b44a8cc

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel