MIPS: Unify memcpy.S and memcpy-inatomic.S

We can save the 451 lines of code that comprise memcpy-inatomic.S at the
expense of a single instruction in the memcpy prolog.  We also use an
additional register (t6), so this may cause increased register pressure in
some places as well.  But I think the reduced maintenance burden, of not
having two nearly identical implementations, makes it worth it.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 12 insertions, 452 deletions

diff --git a/arch/mips/lib/Makefile b/arch/mips/lib/Makefile
index 2a7c74fc15fc..399a50a541d4 100644
--- a/arch/mips/lib/Makefile
+++ b/arch/mips/lib/Makefile
@@ -2,7 +2,7 @@
 # Makefile for MIPS-specific library files..
 #
 
-lib-y   += csum_partial.o delay.o memcpy.o memcpy-inatomic.o memset.o \
+lib-y   += csum_partial.o delay.o memcpy.o memset.o \
            strlen_user.o strncpy_user.o strnlen_user.o uncached.o
 
 obj-y                   += iomap.o
diff --git a/arch/mips/lib/memcpy-inatomic.S b/arch/mips/lib/memcpy-inatomic.S
deleted file mode 100644
index 68853a038d3f..000000000000
--- a/arch/mips/lib/memcpy-inatomic.S
+++ /dev/null
@@ -1,451 +0,0 @@
-/*
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Unified implementation of memcpy, memmove and the __copy_user backend.
- *
- * Copyright (C) 1998, 99, 2000, 01, 2002 Ralf Baechle (ralf@gnu.org)
- * Copyright (C) 1999, 2000, 01, 2002 Silicon Graphics, Inc.
- * Copyright (C) 2002 Broadcom, Inc.
- *   memcpy/copy_user author: Mark Vandevoorde
- * Copyright (C) 2007  Maciej W. Rozycki
- *
- * Mnemonic names for arguments to memcpy/__copy_user
- */
-
-/*
- * Hack to resolve longstanding prefetch issue
- *
- * Prefetching may be fatal on some systems if we're prefetching beyond the
- * end of memory on some systems.  It's also a seriously bad idea on non
- * dma-coherent systems.
- */
-#ifdef CONFIG_DMA_NONCOHERENT
-#undef CONFIG_CPU_HAS_PREFETCH
-#endif
-#ifdef CONFIG_MIPS_MALTA
-#undef CONFIG_CPU_HAS_PREFETCH
-#endif
-
-#include <asm/asm.h>
-#include <asm/asm-offsets.h>
-#include <asm/regdef.h>
-
-#define dst a0
-#define src a1
-#define len a2
-
-/*
- * Spec
- *
- * memcpy copies len bytes from src to dst and sets v0 to dst.
- * It assumes that
- *   - src and dst don't overlap
- *   - src is readable
- *   - dst is writable
- * memcpy uses the standard calling convention
- *
- * __copy_user copies up to len bytes from src to dst and sets a2 (len) to
- * the number of uncopied bytes due to an exception caused by a read or write.
- * __copy_user assumes that src and dst don't overlap, and that the call is
- * implementing one of the following:
- *   copy_to_user
- *     - src is readable  (no exceptions when reading src)
- *   copy_from_user
- *     - dst is writable  (no exceptions when writing dst)
- * __copy_user uses a non-standard calling convention; see
- * include/asm-mips/uaccess.h
- *
- * When an exception happens on a load, the handler must
- # ensure that all of the destination buffer is overwritten to prevent
- * leaking information to user mode programs.
- */
-
-/*
- * Implementation
- */
-
-/*
- * The exception handler for loads requires that:
- *  1- AT contain the address of the byte just past the end of the source
- *     of the copy,
- *  2- src_entry <= src < AT, and
- *  3- (dst - src) == (dst_entry - src_entry),
- * The _entry suffix denotes values when __copy_user was called.
- *
- * (1) is set up up by uaccess.h and maintained by not writing AT in copy_user
- * (2) is met by incrementing src by the number of bytes copied
- * (3) is met by not doing loads between a pair of increments of dst and src
- *
- * The exception handlers for stores adjust len (if necessary) and return.
- * These handlers do not need to overwrite any data.
- *
- * For __rmemcpy and memmove an exception is always a kernel bug, therefore
- * they're not protected.
- */
-
-#define EXC(inst_reg,addr,handler)              \
-9:      inst_reg, addr;                         \
-        .section __ex_table,"a";                \
-        PTR     9b, handler;                    \
-        .previous
-
-/*
- * Only on the 64-bit kernel we can made use of 64-bit registers.
- */
-#ifdef CONFIG_64BIT
-#define USE_DOUBLE
-#endif
-
-#ifdef USE_DOUBLE
-
-#define LOAD   ld
-#define LOADL  ldl
-#define LOADR  ldr
-#define STOREL sdl
-#define STORER sdr
-#define STORE  sd
-#define ADD    daddu
-#define SUB    dsubu
-#define SRL    dsrl
-#define SRA    dsra
-#define SLL    dsll
-#define SLLV   dsllv
-#define SRLV   dsrlv
-#define NBYTES 8
-#define LOG_NBYTES 3
-
-/*
- * As we are sharing code base with the mips32 tree (which use the o32 ABI
- * register definitions). We need to redefine the register definitions from
- * the n64 ABI register naming to the o32 ABI register naming.
- */
-#undef t0
-#undef t1
-#undef t2
-#undef t3
-#define t0      $8
-#define t1      $9
-#define t2      $10
-#define t3      $11
-#define t4      $12
-#define t5      $13
-#define t6      $14
-#define t7      $15
-
-#else
-
-#define LOAD   lw
-#define LOADL  lwl
-#define LOADR  lwr
-#define STOREL swl
-#define STORER swr
-#define STORE  sw
-#define ADD    addu
-#define SUB    subu
-#define SRL    srl
-#define SLL    sll
-#define SRA    sra
-#define SLLV   sllv
-#define SRLV   srlv
-#define NBYTES 4
-#define LOG_NBYTES 2
-
-#endif /* USE_DOUBLE */
-
-#ifdef CONFIG_CPU_LITTLE_ENDIAN
-#define LDFIRST LOADR
-#define LDREST  LOADL
-#define STFIRST STORER
-#define STREST  STOREL
-#define SHIFT_DISCARD SLLV
-#else
-#define LDFIRST LOADL
-#define LDREST  LOADR
-#define STFIRST STOREL
-#define STREST  STORER
-#define SHIFT_DISCARD SRLV
-#endif
-
-#define FIRST(unit) ((unit)*NBYTES)
-#define REST(unit)  (FIRST(unit)+NBYTES-1)
-#define UNIT(unit)  FIRST(unit)
-
-#define ADDRMASK (NBYTES-1)
-
-        .text
-        .set    noreorder
-#ifndef CONFIG_CPU_DADDI_WORKAROUNDS
-        .set    noat
-#else
-        .set    at=v1
-#endif
-
-/*
- * A combined memcpy/__copy_user
- * __copy_user sets len to 0 for success; else to an upper bound of
- * the number of uncopied bytes.
- * memcpy sets v0 to dst.
- */
-        .align  5
-LEAF(__copy_user_inatomic)
-        /*
-         * Note: dst & src may be unaligned, len may be 0
-         * Temps
-         */
-#define rem t8
-
-        /*
-         * The "issue break"s below are very approximate.
-         * Issue delays for dcache fills will perturb the schedule, as will
-         * load queue full replay traps, etc.
-         *
-         * If len < NBYTES use byte operations.
-         */
-        PREF(   0, 0(src) )
-        PREF(   1, 0(dst) )
-        sltu    t2, len, NBYTES
-        and     t1, dst, ADDRMASK
-        PREF(   0, 1*32(src) )
-        PREF(   1, 1*32(dst) )
-        bnez    t2, .Lcopy_bytes_checklen
-         and    t0, src, ADDRMASK
-        PREF(   0, 2*32(src) )
-        PREF(   1, 2*32(dst) )
-        bnez    t1, .Ldst_unaligned
-         nop
-        bnez    t0, .Lsrc_unaligned_dst_aligned
-        /*
-         * use delay slot for fall-through
-         * src and dst are aligned; need to compute rem
-         */
-.Lboth_aligned:
-         SRL    t0, len, LOG_NBYTES+3           # +3 for 8 units/iter
-        beqz    t0, .Lcleanup_both_aligned      # len < 8*NBYTES
-         and    rem, len, (8*NBYTES-1)          # rem = len % (8*NBYTES)
-        PREF(   0, 3*32(src) )
-        PREF(   1, 3*32(dst) )
-        .align  4
-1:
-EXC(    LOAD    t0, UNIT(0)(src),       .Ll_exc)
-EXC(    LOAD    t1, UNIT(1)(src),       .Ll_exc_copy)
-EXC(    LOAD    t2, UNIT(2)(src),       .Ll_exc_copy)
-EXC(    LOAD    t3, UNIT(3)(src),       .Ll_exc_copy)
-        SUB     len, len, 8*NBYTES
-EXC(    LOAD    t4, UNIT(4)(src),       .Ll_exc_copy)
-EXC(    LOAD    t7, UNIT(5)(src),       .Ll_exc_copy)
-        STORE   t0, UNIT(0)(dst)
-        STORE   t1, UNIT(1)(dst)
-EXC(    LOAD    t0, UNIT(6)(src),       .Ll_exc_copy)
-EXC(    LOAD    t1, UNIT(7)(src),       .Ll_exc_copy)
-        ADD     src, src, 8*NBYTES
-        ADD     dst, dst, 8*NBYTES
-        STORE   t2, UNIT(-6)(dst)
-        STORE   t3, UNIT(-5)(dst)
-        STORE   t4, UNIT(-4)(dst)
-        STORE   t7, UNIT(-3)(dst)
-        STORE   t0, UNIT(-2)(dst)
-        STORE   t1, UNIT(-1)(dst)
-        PREF(   0, 8*32(src) )
-        PREF(   1, 8*32(dst) )
-        bne     len, rem, 1b
-         nop
-
-        /*
-         * len == rem == the number of bytes left to copy < 8*NBYTES
-         */
-.Lcleanup_both_aligned:
-        beqz    len, .Ldone
-         sltu   t0, len, 4*NBYTES
-        bnez    t0, .Lless_than_4units
-         and    rem, len, (NBYTES-1)    # rem = len % NBYTES
-        /*
-         * len >= 4*NBYTES
-         */
-EXC(    LOAD    t0, UNIT(0)(src),       .Ll_exc)
-EXC(    LOAD    t1, UNIT(1)(src),       .Ll_exc_copy)
-EXC(    LOAD    t2, UNIT(2)(src),       .Ll_exc_copy)
-EXC(    LOAD    t3, UNIT(3)(src),       .Ll_exc_copy)
-        SUB     len, len, 4*NBYTES
-        ADD     src, src, 4*NBYTES
-        STORE   t0, UNIT(0)(dst)
-        STORE   t1, UNIT(1)(dst)
-        STORE   t2, UNIT(2)(dst)
-        STORE   t3, UNIT(3)(dst)
-        .set    reorder                         /* DADDI_WAR */
-        ADD     dst, dst, 4*NBYTES
-        beqz    len, .Ldone
-        .set    noreorder
-.Lless_than_4units:
-        /*
-         * rem = len % NBYTES
-         */
-        beq     rem, len, .Lcopy_bytes
-         nop
-1:
-EXC(    LOAD    t0, 0(src),             .Ll_exc)
-        ADD     src, src, NBYTES
-        SUB     len, len, NBYTES
-        STORE   t0, 0(dst)
-        .set    reorder                         /* DADDI_WAR */
-        ADD     dst, dst, NBYTES
-        bne     rem, len, 1b
-        .set    noreorder
-
-        /*
-         * 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
-         * mispredicts.  Can't do an explicit LOAD dst,mask,or,STORE
-         * because can't assume read-access to dst.  Instead, use
-         * STREST dst, which doesn't require read access to dst.
-         *
-         * This code should perform better than a simple loop on modern,
-         * wide-issue mips processors because the code has fewer branches and
-         * more instruction-level parallelism.
-         */
-#define bits t2
-        beqz    len, .Ldone
-         ADD    t1, dst, len    # t1 is just past last byte of dst
-        li      bits, 8*NBYTES
-        SLL     rem, len, 3     # rem = number of bits to keep
-EXC(    LOAD    t0, 0(src),             .Ll_exc)
-        SUB     bits, bits, rem # bits = number of bits to discard
-        SHIFT_DISCARD t0, t0, bits
-        STREST  t0, -1(t1)
-        jr      ra
-         move   len, zero
-.Ldst_unaligned:
-        /*
-         * dst is unaligned
-         * t0 = src & ADDRMASK
-         * t1 = dst & ADDRMASK; T1 > 0
-         * len >= NBYTES
-         *
-         * Copy enough bytes to align dst
-         * Set match = (src and dst have same alignment)
-         */
-#define match rem
-EXC(    LDFIRST t3, FIRST(0)(src),      .Ll_exc)
-        ADD     t2, zero, NBYTES
-EXC(    LDREST  t3, REST(0)(src),       .Ll_exc_copy)
-        SUB     t2, t2, t1      # t2 = number of bytes copied
-        xor     match, t0, t1
-        STFIRST t3, FIRST(0)(dst)
-        beq     len, t2, .Ldone
-         SUB    len, len, t2
-        ADD     dst, dst, t2
-        beqz    match, .Lboth_aligned
-         ADD    src, src, t2
-
-.Lsrc_unaligned_dst_aligned:
-        SRL     t0, len, LOG_NBYTES+2    # +2 for 4 units/iter
-        PREF(   0, 3*32(src) )
-        beqz    t0, .Lcleanup_src_unaligned
-         and    rem, len, (4*NBYTES-1)   # rem = len % 4*NBYTES
-        PREF(   1, 3*32(dst) )
-1:
-/*
- * Avoid consecutive LD*'s to the same register since some mips
- * implementations can't issue them in the same cycle.
- * It's OK to load FIRST(N+1) before REST(N) because the two addresses
- * are to the same unit (unless src is aligned, but it's not).
- */
-EXC(    LDFIRST t0, FIRST(0)(src),      .Ll_exc)
-EXC(    LDFIRST t1, FIRST(1)(src),      .Ll_exc_copy)
-        SUB     len, len, 4*NBYTES
-EXC(    LDREST  t0, REST(0)(src),       .Ll_exc_copy)
-EXC(    LDREST  t1, REST(1)(src),       .Ll_exc_copy)
-EXC(    LDFIRST t2, FIRST(2)(src),      .Ll_exc_copy)
-EXC(    LDFIRST t3, FIRST(3)(src),      .Ll_exc_copy)
-EXC(    LDREST  t2, REST(2)(src),       .Ll_exc_copy)
-EXC(    LDREST  t3, REST(3)(src),       .Ll_exc_copy)
-        PREF(   0, 9*32(src) )          # 0 is PREF_LOAD  (not streamed)
-        ADD     src, src, 4*NBYTES
-#ifdef CONFIG_CPU_SB1
-        nop                             # improves slotting
-#endif
-        STORE   t0, UNIT(0)(dst)
-        STORE   t1, UNIT(1)(dst)
-        STORE   t2, UNIT(2)(dst)
-        STORE   t3, UNIT(3)(dst)
-        PREF(   1, 9*32(dst) )          # 1 is PREF_STORE (not streamed)
-        .set    reorder                         /* DADDI_WAR */
-        ADD     dst, dst, 4*NBYTES
-        bne     len, rem, 1b
-        .set    noreorder
-
-.Lcleanup_src_unaligned:
-        beqz    len, .Ldone
-         and    rem, len, NBYTES-1  # rem = len % NBYTES
-        beq     rem, len, .Lcopy_bytes
-         nop
-1:
-EXC(    LDFIRST t0, FIRST(0)(src),      .Ll_exc)
-EXC(    LDREST  t0, REST(0)(src),       .Ll_exc_copy)
-        ADD     src, src, NBYTES
-        SUB     len, len, NBYTES
-        STORE   t0, 0(dst)
-        .set    reorder                         /* DADDI_WAR */
-        ADD     dst, dst, NBYTES
-        bne     len, rem, 1b
-        .set    noreorder
-
-.Lcopy_bytes_checklen:
-        beqz    len, .Ldone
-         nop
-.Lcopy_bytes:
-        /* 0 < len < NBYTES  */
-#define COPY_BYTE(N)                    \
-EXC(    lb      t0, N(src), .Ll_exc);   \
-        SUB     len, len, 1;            \
-        beqz    len, .Ldone;            \
-         sb     t0, N(dst)
-
-        COPY_BYTE(0)
-        COPY_BYTE(1)
-#ifdef USE_DOUBLE
-        COPY_BYTE(2)
-        COPY_BYTE(3)
-        COPY_BYTE(4)
-        COPY_BYTE(5)
-#endif
-EXC(    lb      t0, NBYTES-2(src), .Ll_exc)
-        SUB     len, len, 1
-        jr      ra
-         sb     t0, NBYTES-2(dst)
-.Ldone:
-        jr      ra
-         nop
-        END(__copy_user_inatomic)
-
-.Ll_exc_copy:
-        /*
-         * Copy bytes from src until faulting load address (or until a
-         * lb faults)
-         *
-         * When reached by a faulting LDFIRST/LDREST, THREAD_BUADDR($28)
-         * may be more than a byte beyond the last address.
-         * Hence, the lb below may get an exception.
-         *
-         * Assumes src < THREAD_BUADDR($28)
-         */
-        LOAD    t0, TI_TASK($28)
-         nop
-        LOAD    t0, THREAD_BUADDR(t0)
-1:
-EXC(    lb      t1, 0(src),     .Ll_exc)
-        ADD     src, src, 1
-        sb      t1, 0(dst)      # can't fault -- we're copy_from_user
-        .set    reorder                         /* DADDI_WAR */
-        ADD     dst, dst, 1
-        bne     src, t0, 1b
-        .set    noreorder
-.Ll_exc:
-        LOAD    t0, TI_TASK($28)
-         nop
-        LOAD    t0, THREAD_BUADDR(t0)   # t0 is just past last good address
-         nop
-        SUB     len, AT, t0             # len number of uncopied bytes
-        jr      ra
-         nop
diff --git a/arch/mips/lib/memcpy.S b/arch/mips/lib/memcpy.S
index 56a1f85a1ce8..65192c06781e 100644
--- a/arch/mips/lib/memcpy.S
+++ b/arch/mips/lib/memcpy.S
@@ -183,6 +183,14 @@
 #endif
 
 /*
+ * t6 is used as a flag to note inatomic mode.
+ */
+LEAF(__copy_user_inatomic)
+        b       __copy_user_common
+         li     t6, 1
+        END(__copy_user_inatomic)
+
+/*
  * A combined memcpy/__copy_user
  * __copy_user sets len to 0 for success; else to an upper bound of
  * the number of uncopied bytes.
@@ -193,6 +201,8 @@ LEAF(memcpy)					/* a0=dst a1=src a2=len */
         move    v0, dst                         /* return value */
 .L__memcpy:
 FEXPORT(__copy_user)
+        li      t6, 0   /* not inatomic */
+__copy_user_common:
         /*
          * Note: dst & src may be unaligned, len may be 0
          * Temps
@@ -458,6 +468,7 @@ EXC(	lb	t1, 0(src),	.Ll_exc)
         LOAD    t0, THREAD_BUADDR(t0)   # t0 is just past last good address
          nop
         SUB     len, AT, t0             # len number of uncopied bytes
+        bnez    t6, .Ldone      /* Skip the zeroing part if inatomic */
         /*
          * Here's where we rely on src and dst being incremented in tandem,
          *   See (3) above.