diff options
author | Alexander Lobakin <alobakin@dlink.ru> | 2020-01-22 13:58:50 +0300 |
---|---|---|
committer | Paul Burton <paulburton@kernel.org> | 2020-01-22 10:16:47 -0800 |
commit | 18d84e2e55b6abe1e5b8a658ad078796122899fb (patch) | |
tree | e31bb34a5203c09d6aa16a06f4d2c25ff6ba6039 /arch | |
parent | 7de86604bbe4ecb3da0c8c40d4e4b1549e879f92 (diff) | |
download | linux-18d84e2e55b6abe1e5b8a658ad078796122899fb.tar.gz linux-18d84e2e55b6abe1e5b8a658ad078796122899fb.tar.bz2 linux-18d84e2e55b6abe1e5b8a658ad078796122899fb.zip |
MIPS: make CPU_HAS_LOAD_STORE_LR opt-out
CPU_HAS_LOAD_STORE_LR was introduced in 932afdeec18b ("MIPS: Add Kconfig
variable for CPUs with unaligned load/store instructions") to make code
in kernel/unaligned.c and lib/mem{cpy,set}.S more intuitive and give a
possibility to easily add new CPUs without these instruction sets in
future.
Hovewer, this variant is not optimal for mainly two reasons:
* For now, we have 20+ CPUs with such instructions and only two (MIPS R6)
without. It will obviously be more effective and straightforward to
have an option for these two rather than for the rest.
* You can easily miss the fact that you need to select this option when
adding a new CPU, while all processors lacking these sets are
well-known, so the probability of missing something is way much lower.
We can address both points by turning CPU_HAS_LOAD_STORE_LR into opt-out
CPU_NO_LOAD_STORE_LR. This also makes MIPS root Kconfig more clear and
understandable.
Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>
Signed-off-by: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>
Cc: Will Deacon <will@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Allison Randal <allison@lohutok.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Diffstat (limited to 'arch')
-rw-r--r-- | arch/mips/Kconfig | 34 | ||||
-rw-r--r-- | arch/mips/kernel/unaligned.c | 36 | ||||
-rw-r--r-- | arch/mips/lib/memcpy.S | 14 | ||||
-rw-r--r-- | arch/mips/lib/memset.S | 16 |
4 files changed, 40 insertions, 60 deletions
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index c5498146bd3b..8ff846ef2345 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -1218,8 +1218,7 @@ config NO_IOPORT_MAP def_bool n config GENERIC_CSUM - bool - default y if !CPU_HAS_LOAD_STORE_LR + def_bool CPU_NO_LOAD_STORE_LR config GENERIC_ISA_DMA bool @@ -1441,7 +1440,6 @@ config CPU_LOONGSON64 select CPU_SUPPORTS_HIGHMEM select CPU_SUPPORTS_HUGEPAGES select CPU_SUPPORTS_MSA - select CPU_HAS_LOAD_STORE_LR select WEAK_ORDERING select WEAK_REORDERING_BEYOND_LLSC select MIPS_ASID_BITS_VARIABLE @@ -1537,7 +1535,6 @@ config CPU_MIPS32_R1 bool "MIPS32 Release 1" depends on SYS_HAS_CPU_MIPS32_R1 select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_HIGHMEM help @@ -1555,7 +1552,6 @@ config CPU_MIPS32_R2 bool "MIPS32 Release 2" depends on SYS_HAS_CPU_MIPS32_R2 select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_HIGHMEM select CPU_SUPPORTS_MSA @@ -1571,6 +1567,7 @@ config CPU_MIPS32_R6 bool "MIPS32 Release 6" depends on SYS_HAS_CPU_MIPS32_R6 select CPU_HAS_PREFETCH + select CPU_NO_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_HIGHMEM select CPU_SUPPORTS_MSA @@ -1586,7 +1583,6 @@ config CPU_MIPS64_R1 bool "MIPS64 Release 1" depends on SYS_HAS_CPU_MIPS64_R1 select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HIGHMEM @@ -1606,7 +1602,6 @@ config CPU_MIPS64_R2 bool "MIPS64 Release 2" depends on SYS_HAS_CPU_MIPS64_R2 select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HIGHMEM @@ -1624,6 +1619,7 @@ config CPU_MIPS64_R6 bool "MIPS64 Release 6" depends on SYS_HAS_CPU_MIPS64_R6 select CPU_HAS_PREFETCH + select CPU_NO_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HIGHMEM @@ -1641,7 +1637,6 @@ config CPU_R3000 bool "R3000" depends on SYS_HAS_CPU_R3000 select CPU_HAS_WB - select CPU_HAS_LOAD_STORE_LR select CPU_R3K_TLB select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_HIGHMEM @@ -1657,7 +1652,6 @@ config CPU_TX39XX bool "R39XX" depends on SYS_HAS_CPU_TX39XX select CPU_SUPPORTS_32BIT_KERNEL - select CPU_HAS_LOAD_STORE_LR select CPU_R3K_TLB config CPU_VR41XX @@ -1665,7 +1659,6 @@ config CPU_VR41XX depends on SYS_HAS_CPU_VR41XX select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL - select CPU_HAS_LOAD_STORE_LR help The options selects support for the NEC VR4100 series of processors. Only choose this option if you have one of these processors as a @@ -1678,7 +1671,6 @@ config CPU_R4X00 select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HUGEPAGES - select CPU_HAS_LOAD_STORE_LR help MIPS Technologies R4000-series processors other than 4300, including the R4000, R4400, R4600, and 4700. @@ -1687,7 +1679,6 @@ config CPU_TX49XX bool "R49XX" depends on SYS_HAS_CPU_TX49XX select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HUGEPAGES @@ -1698,7 +1689,6 @@ config CPU_R5000 select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HUGEPAGES - select CPU_HAS_LOAD_STORE_LR help MIPS Technologies R5000-series processors other than the Nevada. @@ -1708,7 +1698,6 @@ config CPU_R5500 select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HUGEPAGES - select CPU_HAS_LOAD_STORE_LR help NEC VR5500 and VR5500A series processors implement 64-bit MIPS IV instruction set. @@ -1719,7 +1708,6 @@ config CPU_NEVADA select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HUGEPAGES - select CPU_HAS_LOAD_STORE_LR help QED / PMC-Sierra RM52xx-series ("Nevada") processors. @@ -1727,7 +1715,6 @@ config CPU_R10000 bool "R10000" depends on SYS_HAS_CPU_R10000 select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HIGHMEM @@ -1739,7 +1726,6 @@ config CPU_RM7000 bool "RM7000" depends on SYS_HAS_CPU_RM7000 select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HIGHMEM @@ -1748,7 +1734,6 @@ config CPU_RM7000 config CPU_SB1 bool "SB1" depends on SYS_HAS_CPU_SB1 - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HIGHMEM @@ -1759,7 +1744,6 @@ config CPU_CAVIUM_OCTEON bool "Cavium Octeon processor" depends on SYS_HAS_CPU_CAVIUM_OCTEON select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_64BIT_KERNEL select WEAK_ORDERING select CPU_SUPPORTS_HIGHMEM @@ -1789,7 +1773,6 @@ config CPU_BMIPS select WEAK_ORDERING select CPU_SUPPORTS_HIGHMEM select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_CPUFREQ select MIPS_EXTERNAL_TIMER help @@ -1798,7 +1781,6 @@ config CPU_BMIPS config CPU_XLR bool "Netlogic XLR SoC" depends on SYS_HAS_CPU_XLR - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_64BIT_KERNEL select CPU_SUPPORTS_HIGHMEM @@ -1817,7 +1799,6 @@ config CPU_XLP select WEAK_ORDERING select WEAK_REORDERING_BEYOND_LLSC select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_MIPSR2 select CPU_SUPPORTS_HUGEPAGES select MIPS_ASID_BITS_VARIABLE @@ -1923,14 +1904,12 @@ config CPU_LOONGSON2EF select CPU_SUPPORTS_HIGHMEM select CPU_SUPPORTS_HUGEPAGES select ARCH_HAS_PHYS_TO_DMA - select CPU_HAS_LOAD_STORE_LR config CPU_LOONGSON32 bool select CPU_MIPS32 select CPU_MIPSR2 select CPU_HAS_PREFETCH - select CPU_HAS_LOAD_STORE_LR select CPU_SUPPORTS_32BIT_KERNEL select CPU_SUPPORTS_HIGHMEM select CPU_SUPPORTS_CPUFREQ @@ -2573,12 +2552,13 @@ config XKS01 config CPU_HAS_RIXI bool -config CPU_HAS_LOAD_STORE_LR +config CPU_NO_LOAD_STORE_LR bool help - CPU has support for unaligned load and store instructions: + CPU lacks support for unaligned load and store instructions: LWL, LWR, SWL, SWR (Load/store word left/right). - LDL, LDR, SDL, SDR (Load/store doubleword left/right, for 64bit systems). + LDL, LDR, SDL, SDR (Load/store doubleword left/right, for 64bit + systems). # # Vectored interrupt mode is an R2 feature diff --git a/arch/mips/kernel/unaligned.c b/arch/mips/kernel/unaligned.c index 92bd2b0f0548..ca6fc4762d97 100644 --- a/arch/mips/kernel/unaligned.c +++ b/arch/mips/kernel/unaligned.c @@ -131,7 +131,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR #define _LoadW(addr, value, res, type) \ do { \ __asm__ __volatile__ ( \ @@ -152,7 +152,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#else /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#else /* CONFIG_CPU_NO_LOAD_STORE_LR */ /* For CPUs without lwl instruction */ #define _LoadW(addr, value, res, type) \ do { \ @@ -187,7 +187,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#endif /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ #define _LoadHWU(addr, value, res, type) \ do { \ @@ -213,7 +213,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR #define _LoadWU(addr, value, res, type) \ do { \ __asm__ __volatile__ ( \ @@ -256,7 +256,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#else /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#else /* CONFIG_CPU_NO_LOAD_STORE_LR */ /* For CPUs without lwl and ldl instructions */ #define _LoadWU(addr, value, res, type) \ do { \ @@ -340,7 +340,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#endif /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ #define _StoreHW(addr, value, res, type) \ @@ -366,7 +366,7 @@ do { \ : "r" (value), "r" (addr), "i" (-EFAULT));\ } while(0) -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR #define _StoreW(addr, value, res, type) \ do { \ __asm__ __volatile__ ( \ @@ -407,7 +407,7 @@ do { \ : "r" (value), "r" (addr), "i" (-EFAULT)); \ } while(0) -#else /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#else /* CONFIG_CPU_NO_LOAD_STORE_LR */ #define _StoreW(addr, value, res, type) \ do { \ __asm__ __volatile__ ( \ @@ -483,7 +483,7 @@ do { \ : "memory"); \ } while(0) -#endif /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ #else /* __BIG_ENDIAN */ @@ -509,7 +509,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR #define _LoadW(addr, value, res, type) \ do { \ __asm__ __volatile__ ( \ @@ -530,7 +530,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#else /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#else /* CONFIG_CPU_NO_LOAD_STORE_LR */ /* For CPUs without lwl instruction */ #define _LoadW(addr, value, res, type) \ do { \ @@ -565,7 +565,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#endif /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ #define _LoadHWU(addr, value, res, type) \ @@ -592,7 +592,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR #define _LoadWU(addr, value, res, type) \ do { \ __asm__ __volatile__ ( \ @@ -635,7 +635,7 @@ do { \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#else /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#else /* CONFIG_CPU_NO_LOAD_STORE_LR */ /* For CPUs without lwl and ldl instructions */ #define _LoadWU(addr, value, res, type) \ do { \ @@ -718,7 +718,7 @@ do { \ : "=&r" (value), "=r" (res) \ : "r" (addr), "i" (-EFAULT)); \ } while(0) -#endif /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ #define _StoreHW(addr, value, res, type) \ do { \ @@ -743,7 +743,7 @@ do { \ : "r" (value), "r" (addr), "i" (-EFAULT));\ } while(0) -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR #define _StoreW(addr, value, res, type) \ do { \ __asm__ __volatile__ ( \ @@ -784,7 +784,7 @@ do { \ : "r" (value), "r" (addr), "i" (-EFAULT)); \ } while(0) -#else /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#else /* CONFIG_CPU_NO_LOAD_STORE_LR */ /* For CPUs without swl and sdl instructions */ #define _StoreW(addr, value, res, type) \ do { \ @@ -861,7 +861,7 @@ do { \ : "memory"); \ } while(0) -#endif /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ #endif #define LoadHWU(addr, value, res) _LoadHWU(addr, value, res, kernel) diff --git a/arch/mips/lib/memcpy.S b/arch/mips/lib/memcpy.S index cdd19d8561e8..f7994d936505 100644 --- a/arch/mips/lib/memcpy.S +++ b/arch/mips/lib/memcpy.S @@ -301,14 +301,14 @@ and t0, src, ADDRMASK PREFS( 0, 2*32(src) ) PREFD( 1, 2*32(dst) ) -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR bnez t1, .Ldst_unaligned\@ nop bnez t0, .Lsrc_unaligned_dst_aligned\@ -#else +#else /* CONFIG_CPU_NO_LOAD_STORE_LR */ or t0, t0, t1 bnez t0, .Lcopy_unaligned_bytes\@ -#endif +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ /* * use delay slot for fall-through * src and dst are aligned; need to compute rem @@ -389,7 +389,7 @@ bne rem, len, 1b .set noreorder -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR /* * src and dst are aligned, need to copy rem bytes (rem < NBYTES) * A loop would do only a byte at a time with possible branch @@ -491,7 +491,7 @@ bne len, rem, 1b .set noreorder -#endif /* CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* !CONFIG_CPU_NO_LOAD_STORE_LR */ .Lcopy_bytes_checklen\@: beqz len, .Ldone\@ nop @@ -520,7 +520,7 @@ jr ra nop -#ifndef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifdef CONFIG_CPU_NO_LOAD_STORE_LR .Lcopy_unaligned_bytes\@: 1: COPY_BYTE(0) @@ -534,7 +534,7 @@ ADD src, src, 8 b 1b ADD dst, dst, 8 -#endif /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ .if __memcpy == 1 END(memcpy) .set __memcpy, 0 diff --git a/arch/mips/lib/memset.S b/arch/mips/lib/memset.S index 418611ef13cf..d5449e8a3dfc 100644 --- a/arch/mips/lib/memset.S +++ b/arch/mips/lib/memset.S @@ -115,7 +115,7 @@ #endif .set reorder -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR R10KCBARRIER(0(ra)) #ifdef __MIPSEB__ EX(LONG_S_L, a1, (a0), .Lfirst_fixup\@) /* make word/dword aligned */ @@ -125,7 +125,7 @@ PTR_SUBU a0, t0 /* long align ptr */ PTR_ADDU a2, t0 /* correct size */ -#else /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#else /* CONFIG_CPU_NO_LOAD_STORE_LR */ #define STORE_BYTE(N) \ EX(sb, a1, N(a0), .Lbyte_fixup\@); \ .set noreorder; \ @@ -150,7 +150,7 @@ ori a0, STORMASK xori a0, STORMASK PTR_ADDIU a0, STORSIZE -#endif /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ 1: ori t1, a2, 0x3f /* # of full blocks */ xori t1, 0x3f andi t0, a2, 0x40-STORSIZE @@ -185,7 +185,7 @@ .set noreorder beqz a2, 1f -#ifdef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifndef CONFIG_CPU_NO_LOAD_STORE_LR PTR_ADDU a0, a2 /* What's left */ .set reorder R10KCBARRIER(0(ra)) @@ -194,7 +194,7 @@ #else EX(LONG_S_L, a1, -1(a0), .Llast_fixup\@) #endif -#else +#else /* CONFIG_CPU_NO_LOAD_STORE_LR */ PTR_SUBU t0, $0, a2 .set reorder move a2, zero /* No remaining longs */ @@ -211,7 +211,7 @@ EX(sb, a1, 6(a0), .Lbyte_fixup\@) #endif 0: -#endif +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ 1: move a2, zero jr ra @@ -234,7 +234,7 @@ .hidden __memset .endif -#ifndef CONFIG_CPU_HAS_LOAD_STORE_LR +#ifdef CONFIG_CPU_NO_LOAD_STORE_LR .Lbyte_fixup\@: /* * unset_bytes = (#bytes - (#unaligned bytes)) - (-#unaligned bytes remaining + 1) + 1 @@ -243,7 +243,7 @@ PTR_SUBU a2, t0 PTR_ADDIU a2, 1 jr ra -#endif /* !CONFIG_CPU_HAS_LOAD_STORE_LR */ +#endif /* CONFIG_CPU_NO_LOAD_STORE_LR */ .Lfirst_fixup\@: /* unset_bytes already in a2 */ |