linux-kernel - [PATCH v2 1/3] ARM: use .fpu assembler directives instead of assembler arguments

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Date:   Sun, 19 Apr 2020 14:35:49 +0200
From:   Stefan Agner <stefan@...er.ch>
To:     linux@...linux.org.uk
Cc:     arnd@...db.de, ard.biesheuvel@...aro.org, robin.murphy@....com,
        yamada.masahiro@...ionext.com, ndesaulniers@...gle.com,
        manojgupta@...gle.com, jiancai@...gle.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com, Stefan Agner <stefan@...er.ch>
Subject: [PATCH v2 1/3] ARM: use .fpu assembler directives instead of assembler arguments

Explicit FPU selection has been introduced in commit 1a6be26d5b1a
("[ARM] Enable VFP to be built when non-VFP capable CPUs are selected")
to make use of assembler mnemonics for VFP instructions.

However, clang currently does not support passing assembler flags
like this and errors out with:
clang-10: error: the clang compiler does not support '-Wa,-mfpu=softvfp+vfp'

Make use of the .fpu assembler directives to select the floating point
hardware selectively. Also use the new unified assembler language
mnemonics. This allows to build these procedures with Clang.

Link: https://github.com/ClangBuiltLinux/linux/issues/762
Signed-off-by: Stefan Agner <stefan@...er.ch>
---
Changes in v2:
- Add link in commit message

 arch/arm/vfp/Makefile |  2 --
 arch/arm/vfp/vfphw.S  | 30 +++++++++++++++++++-----------
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/arch/arm/vfp/Makefile b/arch/arm/vfp/Makefile
index 9975b63ac3b0..749901a72d6d 100644
--- a/arch/arm/vfp/Makefile
+++ b/arch/arm/vfp/Makefile
@@ -8,6 +8,4 @@
 # ccflags-y := -DDEBUG
 # asflags-y := -DDEBUG
 
-KBUILD_AFLAGS	:=$(KBUILD_AFLAGS:-msoft-float=-Wa,-mfpu=softvfp+vfp -mfloat-abi=soft)
-
 obj-y		+= vfpmodule.o entry.o vfphw.o vfpsingle.o vfpdouble.o
diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index b2e560290860..e214007a20a2 100644
--- a/arch/arm/vfp/vfphw.S
+++ b/arch/arm/vfp/vfphw.S
@@ -258,11 +258,13 @@ vfp_current_hw_state_address:
 
 ENTRY(vfp_get_float)
 	tbl_branch r0, r3, #3
-	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
-1:	mrc	p10, 0, r0, c\dr, c0, 0	@ fmrs	r0, s0
+	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,
+1:	vmov	r0, s\dr
 	ret	lr
 	.org	1b + 8
-1:	mrc	p10, 0, r0, c\dr, c0, 4	@ fmrs	r0, s1
+	.endr
+	.irp	dr,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
+1:	vmov	r0, s\dr
 	ret	lr
 	.org	1b + 8
 	.endr
@@ -271,10 +273,12 @@ ENDPROC(vfp_get_float)
 ENTRY(vfp_put_float)
 	tbl_branch r1, r3, #3
 	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
-1:	mcr	p10, 0, r0, c\dr, c0, 0	@ fmsr	r0, s0
+1:	vmov	s\dr, r0
 	ret	lr
 	.org	1b + 8
-1:	mcr	p10, 0, r0, c\dr, c0, 4	@ fmsr	r0, s1
+	.endr
+	.irp	dr,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
+1:	vmov	s\dr, r0
 	ret	lr
 	.org	1b + 8
 	.endr
@@ -282,15 +286,17 @@ ENDPROC(vfp_put_float)
 
 ENTRY(vfp_get_double)
 	tbl_branch r0, r3, #3
+	.fpu	vfpv2
 	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
-1:	fmrrd	r0, r1, d\dr
+1:	vmov	r0, r1, d\dr
 	ret	lr
 	.org	1b + 8
 	.endr
 #ifdef CONFIG_VFPv3
 	@ d16 - d31 registers
-	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
-1:	mrrc	p11, 3, r0, r1, c\dr	@ fmrrd	r0, r1, d\dr
+	.fpu	vfpv3
+	.irp	dr,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
+1:	vmov	r0, r1, d\dr
 	ret	lr
 	.org	1b + 8
 	.endr
@@ -304,15 +310,17 @@ ENDPROC(vfp_get_double)
 
 ENTRY(vfp_put_double)
 	tbl_branch r2, r3, #3
+	.fpu	vfpv2
 	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
-1:	fmdrr	d\dr, r0, r1
+1:	vmov	d\dr, r0, r1
 	ret	lr
 	.org	1b + 8
 	.endr
 #ifdef CONFIG_VFPv3
+	.fpu	vfpv3
 	@ d16 - d31 registers
-	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
-1:	mcrr	p11, 3, r0, r1, c\dr	@ fmdrr	r0, r1, d\dr
+	.irp	dr,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
+1:	vmov	d\dr, r0, r1
 	ret	lr
 	.org	1b + 8
 	.endr
-- 
2.25.1