linux-kernel - [PATCH v2 2/3] ARM: use VFP assembler mnemonics in register load/store macros

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Message-Id: <583281a29aa28e510ac56da41a93e3f28486901c.1587299429.git.stefan@agner.ch>
Date:   Sun, 19 Apr 2020 14:35:50 +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 2/3] ARM: use VFP assembler mnemonics in register load/store macros

Clang's integrated assembler does not allow to access the VFP registers
through the coprocessor load/store instructions:
<instantiation>:4:6: error: invalid operand for instruction
 LDC p11, cr0, [r10],#32*4 @ FLDMIAD r10!, {d0-d15}
     ^

Replace the coprocessor load/store instructions with explicit assembler
mnemonics to accessing the floating point coprocessor registers. Use
assembler directives to select the appropriate FPU version.

This allows to build these macros with GNU assembler as well as with
Clang's built-in assembler.

Link: https://github.com/ClangBuiltLinux/linux/issues/905
Signed-off-by: Stefan Agner <stefan@...er.ch>
---
Changes in v2:
- Add link in commit message

 arch/arm/include/asm/vfpmacros.h | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/arch/arm/include/asm/vfpmacros.h b/arch/arm/include/asm/vfpmacros.h
index 628c336e8e3b..947ee5395e1f 100644
--- a/arch/arm/include/asm/vfpmacros.h
+++ b/arch/arm/include/asm/vfpmacros.h
@@ -19,23 +19,25 @@
 
 	@ read all the working registers back into the VFP
 	.macro	VFPFLDMIA, base, tmp
+	.fpu	vfpv2
 #if __LINUX_ARM_ARCH__ < 6
-	LDC	p11, cr0, [\base],#33*4		    @ FLDMIAX \base!, {d0-d15}
+	fldmiax	\base!, {d0-d15}
 #else
-	LDC	p11, cr0, [\base],#32*4		    @ FLDMIAD \base!, {d0-d15}
+	vldmia	\base!, {d0-d15}
 #endif
 #ifdef CONFIG_VFPv3
+	.fpu	vfpv3
 #if __LINUX_ARM_ARCH__ <= 6
 	ldr	\tmp, =elf_hwcap		    @ may not have MVFR regs
 	ldr	\tmp, [\tmp, #0]
 	tst	\tmp, #HWCAP_VFPD32
-	ldclne	p11, cr0, [\base],#32*4		    @ FLDMIAD \base!, {d16-d31}
+	vldmiane \base!, {d16-d31}
 	addeq	\base, \base, #32*4		    @ step over unused register space
 #else
 	VFPFMRX	\tmp, MVFR0			    @ Media and VFP Feature Register 0
 	and	\tmp, \tmp, #MVFR0_A_SIMD_MASK	    @ A_SIMD field
 	cmp	\tmp, #2			    @ 32 x 64bit registers?
-	ldcleq	p11, cr0, [\base],#32*4		    @ FLDMIAD \base!, {d16-d31}
+	vldmiaeq \base!, {d16-d31}
 	addne	\base, \base, #32*4		    @ step over unused register space
 #endif
 #endif
@@ -44,22 +46,23 @@
 	@ write all the working registers out of the VFP
 	.macro	VFPFSTMIA, base, tmp
 #if __LINUX_ARM_ARCH__ < 6
-	STC	p11, cr0, [\base],#33*4		    @ FSTMIAX \base!, {d0-d15}
+	fstmiax	\base!, {d0-d15}
 #else
-	STC	p11, cr0, [\base],#32*4		    @ FSTMIAD \base!, {d0-d15}
+	vstmia	\base!, {d0-d15}
 #endif
 #ifdef CONFIG_VFPv3
+	.fpu	vfpv3
 #if __LINUX_ARM_ARCH__ <= 6
 	ldr	\tmp, =elf_hwcap		    @ may not have MVFR regs
 	ldr	\tmp, [\tmp, #0]
 	tst	\tmp, #HWCAP_VFPD32
-	stclne	p11, cr0, [\base],#32*4		    @ FSTMIAD \base!, {d16-d31}
+	vstmiane \base!, {d16-d31}
 	addeq	\base, \base, #32*4		    @ step over unused register space
 #else
 	VFPFMRX	\tmp, MVFR0			    @ Media and VFP Feature Register 0
 	and	\tmp, \tmp, #MVFR0_A_SIMD_MASK	    @ A_SIMD field
 	cmp	\tmp, #2			    @ 32 x 64bit registers?
-	stcleq	p11, cr0, [\base],#32*4		    @ FSTMIAD \base!, {d16-d31}
+	vstmiaeq \base!, {d16-d31}
 	addne	\base, \base, #32*4		    @ step over unused register space
 #endif
 #endif
-- 
2.25.1