frontend: add armv6 color space converter

1 files changed, 65 insertions, 0 deletions

diff --git a/frontend/cspace_arm.S b/frontend/cspace_arm.S
new file mode 100644
index 0000000..e9d15a5
--- /dev/null
+++ b/frontend/cspace_arm.S
@@ -0,0 +1,65 @@
+/*
+ * (C) Gražvydas "notaz" Ignotas, 2013
+ *
+ * This work is licensed under the terms of GNU GPL version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "arm_features.h"
+
+.text
+.align 2
+
+@ lr=0x001f001f
+@ trashes r11, r12
+.macro bgr555_to_rgb565_one rn
+    and      r11, lr, \rn
+    and      r12, lr, \rn, lsr #5
+    and      \rn, lr, \rn, lsr #10
+    orr      r12, r11, lsl #5
+    orr      \rn, r12, lsl #6
+.endm
+
+.macro pld_ reg offs=#0
+#ifdef HAVE_ARMV6
+    pld      [\reg, \offs]
+#endif
+.endm
+
+.global bgr555_to_rgb565 @ void *dst, const void *src, int bytes
+bgr555_to_rgb565:
+    pld_     r1
+    push     {r4-r11,lr}
+    mov      lr, #0x001f
+    subs     r2, #4*8
+    orr      lr, lr, lsl #16
+    blt      1f
+
+0:
+    ldmia    r1!, {r3-r10}
+    subs     r2, #4*8
+    bgr555_to_rgb565_one r3
+
+    pld_     r1, #32*2
+    bgr555_to_rgb565_one r4
+    bgr555_to_rgb565_one r5
+    bgr555_to_rgb565_one r6
+    bgr555_to_rgb565_one r7
+    bgr555_to_rgb565_one r8
+    bgr555_to_rgb565_one r9
+    bgr555_to_rgb565_one r10
+    stmia    r0!, {r3-r10}
+    bge      0b
+
+1:
+    adds     r2, #4*8
+    popeq    {r4-r11,pc}
+
+2:
+    ldr      r3, [r1], #4
+    subs     r2, #4
+    bgr555_to_rgb565_one r3
+    str      r3, [r0], #4
+    bgt      2b
+
+    pop      {r4-r11,pc}