Move all Advent of Codes into one repo

1 files changed, 23 insertions, 0 deletions

diff --git a/2020/05/seat_id_ssse3.asm b/2020/05/seat_id_ssse3.asm
new file mode 100644
index 0000000..4d51cbe
--- /dev/null
+++ b/2020/05/seat_id_ssse3.asm
@@ -0,0 +1,23 @@
+global seat_id
+
+section .rodata
+    align 16
+    xmm_shuf:   db 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 10, 11, 12, 13, 14, 15
+    xmm_cmp:    db 1, 'RBBBBBBB', 1, 1, 1, 1, 1, 1, 1
+
+section .text
+
+seat_id:
+    movq        xmm0, qword [rdi]       ; load first 8 bytes
+    pshufb      xmm0, [rel xmm_shuf]    ; reverse byte order and already shift left once
+    pcmpeqb     xmm0, [rel xmm_cmp]
+    pmovmskb    eax, xmm0               ; store mask in return value
+    xor         ecx, ecx
+    cmp         byte [rdi + 8], 'R'
+    sete        cl
+    or          eax, ecx
+    shl         eax, 1
+    cmp         byte [rdi + 9], 'R'
+    sete        cl
+    or          eax, ecx
+    ret