arch/sparc: Optimized memcpy, memset, copy_to_user, copy_from_user for M7/M8

New algorithm that takes advantage of the M7/M8 block init store
ASI, ie, overlapping pipelines and miss buffer filling.
Full details in code comments.

Signed-off-by: Babu Moger <babu.moger@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 352 insertions, 0 deletions

diff --git a/arch/sparc/lib/M7memset.S b/arch/sparc/lib/M7memset.S
new file mode 100644
index 000000000000..62ea91b3a6b8
--- /dev/null
+++ b/arch/sparc/lib/M7memset.S
@@ -0,0 +1,352 @@
+/*
+ * M7memset.S: SPARC M7 optimized memset.
+ *
+ * Copyright (c) 2016, Oracle and/or its affiliates.  All rights reserved.
+ */
+
+/*
+ * M7memset.S: M7 optimized memset.
+ *
+ * char *memset(sp, c, n)
+ *
+ * Set an array of n chars starting at sp to the character c.
+ * Return sp.
+ *
+ * Fast assembler language version of the following C-program for memset
+ * which represents the `standard' for the C-library.
+ *
+ *	void *
+ *	memset(void *sp1, int c, size_t n)
+ *	{
+ *	    if (n != 0) {
+ *		char *sp = sp1;
+ *		do {
+ *		    *sp++ = (char)c;
+ *		} while (--n != 0);
+ *	    }
+ *	    return (sp1);
+ *	}
+ *
+ * The algorithm is as follows :
+ *
+ *	For small 6 or fewer bytes stores, bytes will be stored.
+ *
+ *	For less than 32 bytes stores, align the address on 4 byte boundary.
+ *	Then store as many 4-byte chunks, followed by trailing bytes.
+ *
+ *	For sizes greater than 32 bytes, align the address on 8 byte boundary.
+ *	if (count >= 64) {
+ *      	store 8-bytes chunks to align the address on 64 byte boundary
+ *		if (value to be set is zero && count >= MIN_ZERO) {
+ *              	Using BIS stores, set the first long word of each
+ *			64-byte cache line to zero which will also clear the
+ *			other seven long words of the cache line.
+ *       	}
+ *       	else if (count >= MIN_LOOP) {
+ *       		Using BIS stores, set the first long word of each of
+ *              	ST_CHUNK cache lines (64 bytes each) before the main
+ *			loop is entered.
+ *              	In the main loop, continue pre-setting the first long
+ *              	word of each cache line ST_CHUNK lines in advance while
+ *              	setting the other seven long words (56 bytes) of each
+ * 			cache line until fewer than ST_CHUNK*64 bytes remain.
+ *			Then set the remaining seven long words of each cache
+ * 			line that has already had its first long word set.
+ *       	}
+ *       	store remaining data in 64-byte chunks until less than
+ *       	64 bytes remain.
+ *       }
+ *       Store as many 8-byte chunks, followed by trailing bytes.
+ *
+ * BIS = Block Init Store
+ *   Doing the advance store of the first element of the cache line
+ *   initiates the displacement of a cache line while only using a single
+ *   instruction in the pipeline. That avoids various pipeline delays,
+ *   such as filling the miss buffer. The performance effect is
+ *   similar to prefetching for normal stores.
+ *   The special case for zero fills runs faster and uses fewer instruction
+ *   cycles than the normal memset loop.
+ *
+ * We only use BIS for memset of greater than MIN_LOOP bytes because a sequence
+ * BIS stores must be followed by a membar #StoreStore. The benefit of
+ * the BIS store must be balanced against the cost of the membar operation.
+ */
+
+/*
+ * ASI_STBI_P marks the cache line as "least recently used"
+ * which means if many threads are active, it has a high chance
+ * of being pushed out of the cache between the first initializing
+ * store and the final stores.
+ * Thus, we use ASI_STBIMRU_P which marks the cache line as
+ * "most recently used" for all but the last store to the cache line.
+ */
+
+#include <asm/asi.h>
+#include <asm/page.h>
+
+#define ASI_STBI_P      ASI_BLK_INIT_QUAD_LDD_P
+#define ASI_STBIMRU_P   ASI_ST_BLKINIT_MRU_P
+
+
+#define ST_CHUNK        24   /* multiple of 4 due to loop unrolling */
+#define MIN_LOOP        16320
+#define MIN_ZERO        512
+
+	.section	".text"
+	.align		32
+
+/*
+ * Define clear_page(dest) as memset(dest, 0, PAGE_SIZE)
+ * (can create a more optimized version later.)
+ */
+	.globl		M7clear_page
+	.globl		M7clear_user_page
+M7clear_page:		/* clear_page(dest) */
+M7clear_user_page:
+	set	PAGE_SIZE, %o1
+	/* fall through into bzero code */
+
+	.size		M7clear_page,.-M7clear_page
+	.size		M7clear_user_page,.-M7clear_user_page
+
+/*
+ * Define bzero(dest, n) as memset(dest, 0, n)
+ * (can create a more optimized version later.)
+ */
+	.globl		M7bzero
+M7bzero:		/* bzero(dest, size) */
+	mov	%o1, %o2
+	mov	0, %o1
+	/* fall through into memset code */
+
+	.size		M7bzero,.-M7bzero
+
+	.global		M7memset
+	.type		M7memset, #function
+	.register	%g3, #scratch
+M7memset:
+	mov     %o0, %o5                ! copy sp1 before using it
+	cmp     %o2, 7                  ! if small counts, just write bytes
+	bleu,pn %xcc, .wrchar
+	 and     %o1, 0xff, %o1          ! o1 is (char)c
+
+	sll     %o1, 8, %o3
+	or      %o1, %o3, %o1           ! now o1 has 2 bytes of c
+	sll     %o1, 16, %o3
+	cmp     %o2, 32
+	blu,pn  %xcc, .wdalign
+	 or      %o1, %o3, %o1           ! now o1 has 4 bytes of c
+
+	sllx    %o1, 32, %o3
+	or      %o1, %o3, %o1           ! now o1 has 8 bytes of c
+
+.dbalign:
+	andcc   %o5, 7, %o3             ! is sp1 aligned on a 8 byte bound?
+	bz,pt   %xcc, .blkalign         ! already long word aligned
+	 sub     %o3, 8, %o3             ! -(bytes till long word aligned)
+
+	add     %o2, %o3, %o2           ! update o2 with new count
+	! Set -(%o3) bytes till sp1 long word aligned
+1:	stb     %o1, [%o5]              ! there is at least 1 byte to set
+	inccc   %o3                     ! byte clearing loop
+	bl,pt   %xcc, 1b
+	 inc     %o5
+
+	! Now sp1 is long word aligned (sp1 is found in %o5)
+.blkalign:
+	cmp     %o2, 64                 ! check if there are 64 bytes to set
+	blu,pn  %xcc, .wrshort
+	 mov     %o2, %o3
+
+	andcc   %o5, 63, %o3            ! is sp1 block aligned?
+	bz,pt   %xcc, .blkwr            ! now block aligned
+	 sub     %o3, 64, %o3            ! o3 is -(bytes till block aligned)
+	add     %o2, %o3, %o2           ! o2 is the remainder
+
+	! Store -(%o3) bytes till dst is block (64 byte) aligned.
+	! Use long word stores.
+	! Recall that dst is already long word aligned
+1:
+	addcc   %o3, 8, %o3
+	stx     %o1, [%o5]
+	bl,pt   %xcc, 1b
+	 add     %o5, 8, %o5
+
+	! Now sp1 is block aligned
+.blkwr:
+	andn    %o2, 63, %o4            ! calculate size of blocks in bytes
+	brz,pn  %o1, .wrzero            ! special case if c == 0
+	 and     %o2, 63, %o3            ! %o3 = bytes left after blk stores.
+
+	set     MIN_LOOP, %g1
+	cmp     %o4, %g1                ! check there are enough bytes to set
+	blu,pn  %xcc, .short_set        ! to justify cost of membar
+	                                ! must be > pre-cleared lines
+	 nop
+
+	! initial cache-clearing stores
+	! get store pipeline moving
+	rd	%asi, %g3		! save %asi to be restored later
+	wr     %g0, ASI_STBIMRU_P, %asi
+
+	! Primary memset loop for large memsets
+.wr_loop:
+	sub     %o5, 8, %o5		! adjust %o5 for ASI store alignment
+	mov     ST_CHUNK, %g1
+.wr_loop_start:
+	stxa    %o1, [%o5+8]%asi
+	subcc   %g1, 4, %g1
+	stxa    %o1, [%o5+8+64]%asi
+	add     %o5, 256, %o5
+	stxa    %o1, [%o5+8-128]%asi
+	bgu     %xcc, .wr_loop_start
+	 stxa    %o1, [%o5+8-64]%asi
+
+	sub     %o5, ST_CHUNK*64, %o5	! reset %o5
+	mov     ST_CHUNK, %g1
+
+.wr_loop_rest:
+	stxa    %o1, [%o5+8+8]%asi
+	sub     %o4, 64, %o4
+	stxa    %o1, [%o5+16+8]%asi
+	subcc   %g1, 1, %g1
+	stxa    %o1, [%o5+24+8]%asi
+	stxa    %o1, [%o5+32+8]%asi
+	stxa    %o1, [%o5+40+8]%asi
+	add     %o5, 64, %o5
+	stxa    %o1, [%o5-8]%asi
+	bgu     %xcc, .wr_loop_rest
+	 stxa    %o1, [%o5]ASI_STBI_P
+
+	! If more than ST_CHUNK*64 bytes remain to set, continue
+	! setting the first long word of each cache line in advance
+	! to keep the store pipeline moving.
+
+	cmp     %o4, ST_CHUNK*64
+	bge,pt  %xcc, .wr_loop_start
+	 mov     ST_CHUNK, %g1
+
+	brz,a,pn %o4, .asi_done
+	 add     %o5, 8, %o5             ! restore %o5 offset
+
+.wr_loop_small:
+	stxa    %o1, [%o5+8]%asi
+	stxa    %o1, [%o5+8+8]%asi
+	stxa    %o1, [%o5+16+8]%asi
+	stxa    %o1, [%o5+24+8]%asi
+	stxa    %o1, [%o5+32+8]%asi
+	subcc   %o4, 64, %o4
+	stxa    %o1, [%o5+40+8]%asi
+	add     %o5, 64, %o5
+	stxa    %o1, [%o5-8]%asi
+	bgu,pt  %xcc, .wr_loop_small
+	 stxa    %o1, [%o5]ASI_STBI_P
+
+	ba      .asi_done
+	 add     %o5, 8, %o5             ! restore %o5 offset
+
+	! Special case loop for zero fill memsets
+	! For each 64 byte cache line, single STBI to first element
+	! clears line
+.wrzero:
+	cmp     %o4, MIN_ZERO           ! check if enough bytes to set
+					! to pay %asi + membar cost
+	blu     %xcc, .short_set
+	 nop
+	sub     %o4, 256, %o4
+
+.wrzero_loop:
+	mov     64, %g3
+	stxa    %o1, [%o5]ASI_STBI_P
+	subcc   %o4, 256, %o4
+	stxa    %o1, [%o5+%g3]ASI_STBI_P
+	add     %o5, 256, %o5
+	sub     %g3, 192, %g3
+	stxa    %o1, [%o5+%g3]ASI_STBI_P
+	add %g3, 64, %g3
+	bge,pt  %xcc, .wrzero_loop
+	 stxa    %o1, [%o5+%g3]ASI_STBI_P
+	add     %o4, 256, %o4
+
+	brz,pn  %o4, .bsi_done
+	 nop
+
+.wrzero_small:
+	stxa    %o1, [%o5]ASI_STBI_P
+	subcc   %o4, 64, %o4
+	bgu,pt  %xcc, .wrzero_small
+	 add     %o5, 64, %o5
+	ba,a	.bsi_done
+
+.asi_done:
+	wr	%g3, 0x0, %asi		! restored saved %asi
+.bsi_done:
+	membar  #StoreStore             ! required by use of Block Store Init
+
+.short_set:
+	cmp     %o4, 64                 ! check if 64 bytes to set
+	blu     %xcc, 5f
+	 nop
+4:                                      ! set final blocks of 64 bytes
+	stx     %o1, [%o5]
+	stx     %o1, [%o5+8]
+	stx     %o1, [%o5+16]
+	stx     %o1, [%o5+24]
+	subcc   %o4, 64, %o4
+	stx     %o1, [%o5+32]
+	stx     %o1, [%o5+40]
+	add     %o5, 64, %o5
+	stx     %o1, [%o5-16]
+	bgu,pt  %xcc, 4b
+	 stx     %o1, [%o5-8]
+
+5:
+	! Set the remaining long words
+.wrshort:
+	subcc   %o3, 8, %o3             ! Can we store any long words?
+	blu,pn  %xcc, .wrchars
+	 and     %o2, 7, %o2             ! calc bytes left after long words
+6:
+	subcc   %o3, 8, %o3
+	stx     %o1, [%o5]              ! store the long words
+	bgeu,pt %xcc, 6b
+	 add     %o5, 8, %o5
+
+.wrchars:                               ! check for extra chars
+	brnz    %o2, .wrfin
+	 nop
+	retl
+	 nop
+
+.wdalign:
+	andcc   %o5, 3, %o3             ! is sp1 aligned on a word boundary
+	bz,pn   %xcc, .wrword
+	 andn    %o2, 3, %o3             ! create word sized count in %o3
+
+	dec     %o2                     ! decrement count
+	stb     %o1, [%o5]              ! clear a byte
+	b       .wdalign
+	 inc     %o5                     ! next byte
+
+.wrword:
+	subcc   %o3, 4, %o3
+	st      %o1, [%o5]              ! 4-byte writing loop
+	bnz,pt  %xcc, .wrword
+	 add     %o5, 4, %o5
+
+	and     %o2, 3, %o2             ! leftover count, if any
+
+.wrchar:
+	! Set the remaining bytes, if any
+	brz     %o2, .exit
+	 nop
+.wrfin:
+	deccc   %o2
+	stb     %o1, [%o5]
+	bgu,pt  %xcc, .wrfin
+	 inc     %o5
+.exit:
+	retl                            ! %o0 was preserved
+	 nop
+
+	.size		M7memset,.-M7memset