diff options
| author | Stefan Agner <stefan@agner.ch> | 2020-07-09 11:21:27 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@armlinux.org.uk> | 2020-07-21 16:33:39 +0100 |
| commit | 2cbd1cc3dcd3e84be1fc1987da24b190ddf24a70 (patch) | |
| tree | 514c3a84f35df24b98016fa9851ed1fd302fbfdf /arch/arm/include | |
| parent | ee440336e5ef977c397afdb72cbf9c6b8effc8ea (diff) | |
ARM: 8991/1: use VFP assembler mnemonics if available
The integrated assembler of Clang 10 and earlier do not allow to access
the VFP registers through the coprocessor load/store instructions:
arch/arm/vfp/vfpmodule.c:342:2: error: invalid operand for instruction
fmxr(FPEXC, fpexc & ~(FPEXC_EX|FPEXC_DEX|FPEXC_FP2V|FPEXC_VV|FPEXC_TRAP_MASK));
^
arch/arm/vfp/vfpinstr.h:79:6: note: expanded from macro 'fmxr'
asm("mcr p10, 7, %0, " vfpreg(_vfp_) ", cr0, 0 @ fmxr " #_vfp_ ", %0"
^
<inline asm>:1:6: note: instantiated into assembly here
mcr p10, 7, r0, cr8, cr0, 0 @ fmxr FPEXC, r0
^
This has been addressed with Clang 11 [0]. However, to support earlier
versions of Clang and for better readability use of VFP assembler
mnemonics still is preferred.
Ideally we would replace this code with the unified assembler language
mnemonics vmrs/vmsr on call sites along with .fpu assembler directives.
The GNU assembler supports the .fpu directive at least since 2.17 (when
documentation has been added). Since Linux requires binutils 2.21 it is
safe to use .fpu directive. However, binutils does not allow to use
FPINST or FPINST2 as an argument to vmrs/vmsr instructions up to
binutils 2.24 (see binutils commit 16d02dc907c5):
arch/arm/vfp/vfphw.S: Assembler messages:
arch/arm/vfp/vfphw.S:162: Error: operand 0 must be FPSID or FPSCR pr FPEXC -- `vmsr FPINST,r6'
arch/arm/vfp/vfphw.S:165: Error: operand 0 must be FPSID or FPSCR pr FPEXC -- `vmsr FPINST2,r8'
arch/arm/vfp/vfphw.S:235: Error: operand 1 must be a VFP extension System Register -- `vmrs r3,FPINST'
arch/arm/vfp/vfphw.S:238: Error: operand 1 must be a VFP extension System Register -- `vmrs r12,FPINST2'
Use as-instr in Kconfig to check if FPINST/FPINST2 can be used. If they
can be used make use of .fpu directives and UAL VFP mnemonics for
register access.
This allows to build vfpmodule.c with Clang and its integrated assembler.
[0] https://reviews.llvm.org/D59733
Link: https://github.com/ClangBuiltLinux/linux/issues/905
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/include')
| -rw-r--r-- | arch/arm/include/asm/vfp.h | 2 | ||||
| -rw-r--r-- | arch/arm/include/asm/vfpmacros.h | 12 |
2 files changed, 13 insertions, 1 deletions
diff --git a/arch/arm/include/asm/vfp.h b/arch/arm/include/asm/vfp.h index 7157d2a30a49..19928bfb4f9c 100644 --- a/arch/arm/include/asm/vfp.h +++ b/arch/arm/include/asm/vfp.h @@ -9,6 +9,7 @@ #ifndef __ASM_VFP_H #define __ASM_VFP_H +#ifndef CONFIG_AS_VFP_VMRS_FPINST #define FPSID cr0 #define FPSCR cr1 #define MVFR1 cr6 @@ -16,6 +17,7 @@ #define FPEXC cr8 #define FPINST cr9 #define FPINST2 cr10 +#endif /* FPSID bits */ #define FPSID_IMPLEMENTER_BIT (24) diff --git a/arch/arm/include/asm/vfpmacros.h b/arch/arm/include/asm/vfpmacros.h index 947ee5395e1f..ba0d4cb5377e 100644 --- a/arch/arm/include/asm/vfpmacros.h +++ b/arch/arm/include/asm/vfpmacros.h @@ -8,7 +8,16 @@ #include <asm/vfp.h> -@ Macros to allow building with old toolkits (with no VFP support) +#ifdef CONFIG_AS_VFP_VMRS_FPINST + .macro VFPFMRX, rd, sysreg, cond + vmrs\cond \rd, \sysreg + .endm + + .macro VFPFMXR, sysreg, rd, cond + vmsr\cond \sysreg, \rd + .endm +#else + @ Macros to allow building with old toolkits (with no VFP support) .macro VFPFMRX, rd, sysreg, cond MRC\cond p10, 7, \rd, \sysreg, cr0, 0 @ FMRX \rd, \sysreg .endm @@ -16,6 +25,7 @@ .macro VFPFMXR, sysreg, rd, cond MCR\cond p10, 7, \rd, \sysreg, cr0, 0 @ FMXR \sysreg, \rd .endm +#endif @ read all the working registers back into the VFP .macro VFPFLDMIA, base, tmp |