From f7c861e94eb95579c725dcd5d403acd7b4b318e3 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Sun, 9 Jul 2023 21:55:17 +0100
Subject: Assembler optimised blit copy hardcoded to 16x16

---
 src/entities.c |  2 +-
 src/vga.c      | 25 +++++++++++++++++++++++++
 src/vga.h      |  2 ++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/entities.c b/src/entities.c
index e24c119..0471fbc 100644
--- a/src/entities.c
+++ b/src/entities.c
@@ -61,7 +61,7 @@ void entities_draw()
         {
             dst.x = e->ox;
             dst.y = e->oy + MAP_OFFS_Y;
-            blit_copy(&dst);
+            blit_copy16x16(&dst);
             e->erase = 0;
         }
 
diff --git a/src/vga.c b/src/vga.c
index 70a9a67..c78fcec 100644
--- a/src/vga.c
+++ b/src/vga.c
@@ -196,3 +196,28 @@ void blit_copy(const Rect *dst)
         dtarget += 320;
     }
 }
+
+void blit_copy16x16(const Rect *dst)
+{
+    uint8_t *src = buffer + dst->x + dst->y * 320;
+    uint8_t *dtarget = screen + dst->x + dst->y * 320;
+
+    asm volatile (
+        "movl $16, %%eax\n\t"
+        "movl $0x130, %%ebx\n\t"
+        "cld\n\t"
+        "blit_copy16x16_loop:\n\t"
+        "movsl\n\t"
+        "movsl\n\t"
+        "movsl\n\t"
+        "movsl\n\t"
+        "addl %%ebx, %%esi\n\t"
+        "addl %%ebx, %%edi\n\t"
+        "decl %%eax\n\t"
+        "orl %%eax, %%eax\n\t"
+        "jne blit_copy16x16_loop\n\t"
+        : /* no output */
+        : "S" (src), "D" (dtarget)
+        : "ecx", "ebx", "eax"
+    );
+}
diff --git a/src/vga.h b/src/vga.h
index 2441e24..1809c46 100644
--- a/src/vga.h
+++ b/src/vga.h
@@ -36,5 +36,7 @@ void blit_erase(uint8_t c);
 /* copy from back buffer to screen */
 void blit_copy_all();
 void blit_copy(const Rect *dst);
+/* only fot 16x16 rects, w and h are ignored */
+void blit_copy16x16(const Rect *dst);
 
 #endif /* _VGA_H */
-- 
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