Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | [PATCH 2/7] ARM: LTO: avoid THUMB2_KERNEL+LTO | Date | Tue, 20 Feb 2018 22:59:49 +0100 |
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Trying to build an LTO-Enabled kernel with Thumb2 instructions failed horribly for me, with an endless output of things like
ccVnNycO.s:2665: Error: thumb conditional instruction should be in IT block -- `bxne lr' ccVnNycO.s:7128: Error: thumb conditional instruction should be in IT block -- `strexeq r5,r2,[r3]' ccVnNycO.s:7258: Error: thumb conditional instruction should be in IT block -- `strexeq lr,r0,[r3]' ccVnNycO.s:17380: Error: thumb conditional instruction should be in IT block -- `strexeq r1,r2,[r6]' ccVnNycO.s:19163: Error: thumb conditional instruction should be in IT block -- `strexeq r8,r6,[r3]' ccVnNycO.s:22722: Error: thumb conditional instruction should be in IT block -- `strexeq r7,r1,[r0]' ccVnNycO.s:24105: conditional infixes are deprecated in unified syntax ccVnNycO.s:24105: Error: thumb conditional instruction should be in IT block -- `sbcccs r1,r1,r3' ccVnNycO.s:24105: Error: thumb conditional instruction should be in IT block -- `movcc r3,#0' ccVnNycO.s:24210: conditional infixes are deprecated in unified syntax ccVnNycO.s:24210: Error: thumb conditional instruction should be in IT block -- `sbcccs r2,r2,r3' ccVnNycO.s:24210: Error: thumb conditional instruction should be in IT block -- `movcc r3,#0'
I did not investigate this too much, disabling Thumb2 support when LTO is set lets me build randconfig kernels.
Since ARM_SINGLE_ARMV7M is Thumb2-only, I have to disallow LTO for V7-M targets.
Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- arch/arm/Kconfig | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 8ed0f664f86f..fbf2c3ab9a97 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -18,7 +18,7 @@ config ARM select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7 select ARCH_SUPPORTS_ATOMIC_RMW - select ARCH_SUPPORTS_LTO + select ARCH_SUPPORTS_LTO if !ARM_SINGLE_ARMV7M select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_CMPXCHG_LOCKREF select ARCH_WANT_IPC_PARSE_VERSION @@ -1533,6 +1533,7 @@ config SCHED_HRTICK config THUMB2_KERNEL bool "Compile the kernel in Thumb-2 mode" if !CPU_THUMBONLY depends on (CPU_V7 || CPU_V7M) && !CPU_V6 && !CPU_V6K + depends on !LTO default y if CPU_THUMBONLY select ARM_UNWIND help -- 2.9.0
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