1 files changed, 57 insertions, 0 deletions

diff --git a/arch/alpha/lib/strlen.S b/arch/alpha/lib/strlen.S
new file mode 100644
index 000000000000..fe63353de152
--- /dev/null
+++ b/arch/alpha/lib/strlen.S
@@ -0,0 +1,57 @@
+/*
+ * strlen.S (c) 1995 David Mosberger (davidm@cs.arizona.edu)
+ *
+ * Finds length of a 0-terminated string.  Optimized for the
+ * Alpha architecture:
+ *
+ *      - memory accessed as aligned quadwords only
+ *      - uses bcmpge to compare 8 bytes in parallel
+ *      - does binary search to find 0 byte in last
+ *        quadword (HAKMEM needed 12 instructions to
+ *        do this instead of the 9 instructions that
+ *        binary search needs).
+ */
+
+        .set noreorder
+        .set noat
+
+        .align 3
+
+        .globl  strlen
+        .ent    strlen
+
+strlen:
+        ldq_u   $1, 0($16)      # load first quadword ($16  may be misaligned)
+        lda     $2, -1($31)
+        insqh   $2, $16, $2
+        andnot  $16, 7, $0
+        or      $2, $1, $1
+        cmpbge  $31, $1, $2     # $2  <- bitmask: bit i == 1 <==> i-th byte == 0
+        bne     $2, found
+
+loop:   ldq     $1, 8($0)
+        addq    $0, 8, $0       # addr += 8
+        nop                     # helps dual issue last two insns
+        cmpbge  $31, $1, $2
+        beq     $2, loop
+
+found:  blbs    $2, done        # make aligned case fast
+        negq    $2, $3
+        and     $2, $3, $2
+
+        and     $2, 0x0f, $1
+        addq    $0, 4, $3
+        cmoveq  $1, $3, $0
+
+        and     $2, 0x33, $1
+        addq    $0, 2, $3
+        cmoveq  $1, $3, $0
+
+        and     $2, 0x55, $1
+        addq    $0, 1, $3
+        cmoveq  $1, $3, $0
+
+done:   subq    $0, $16, $0
+        ret     $31, ($26)
+
+        .end    strlen