add mem.h and memset32()

src/fb.c

@@ -1,5 +1,6 @@
 #include "fb.h"
 #include <stddef.h>
+#include "mem.h"
 
 static uint32_t * fb;
 static uint32_t fb_width;
@@ -100,13 +101,9 @@ void fb_fill(int x, int y, int width, int height, uint8_t r, uint8_t g, uint8_t
 {
     uint32_t * target = &fb[fb_pitch * y / 4u + x];
     uint32_t pixel = build_pixel(r, g, b);
-    /* TODO: use memset32() */
     for (int row = 0; row < height; row++)
     {
-        for (int col = 0; col < width; col++)
-        {
-            target[col] = pixel;
-        }
+        memset32(target, pixel, width);
         target += fb_pitch / 4u;
     }
 }

src/mem.h

@@ -0,0 +1,15 @@
+#ifndef MEM_H
+#define MEM_H
+
+static inline void memset32(void * dest, uint32_t val, size_t count)
+{
+    uint32_t r0, r1;
+    __asm__ __volatile__ (
+            "cld\n\t"
+            "rep stosl"
+            : "=&c" (r0), "=&D" (r1)
+            : "a" (val), "1" (dest), "0" (count)
+            : "memory");
+}
+
+#endif