hw/display/artist: Delay some variables initialization

We want to have an early exit path. Delay some initializations
before the variables are used.
Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: NSven Schnelle <svens@stackframe.org>
Message-Id: <20200214001303.12873-4-f4bug@amsat.org>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

hw/display/artist.c

@@ -558,7 +558,7 @@ static void draw_line(ARTISTState *s, int x1, int y1, int x2, int y2,
                       bool update_start, int skip_pix, int max_pix)
 {
     struct vram_buffer *buf;
-    uint8_t color = artist_get_color(s);
+    uint8_t color;
     int dx, dy, t, e, x, y, incy, diago, horiz;
     bool c1;
     uint8_t *p;
@@ -569,10 +569,6 @@ static void draw_line(ARTISTState *s, int x1, int y1, int x2, int y2,
         s->vram_start = (x2 << 16) | y2;
     }
 
-    buf = &s->vram_buffer[ARTIST_BUFFER_AP];
-
-    c1 = false;
-
     if (x2 > x1) {
         dx = x2 - x1;
     } else {
@@ -583,6 +579,8 @@ static void draw_line(ARTISTState *s, int x1, int y1, int x2, int y2,
     } else {
         dy = y1 - y2;
     }
+
+    c1 = false;
     if (dy > dx) {
         t = y2;
         y2 = x2;
@@ -620,6 +618,8 @@ static void draw_line(ARTISTState *s, int x1, int y1, int x2, int y2,
     }
     x = x1;
     y = y1;
+    color = artist_get_color(s);
+    buf = &s->vram_buffer[ARTIST_BUFFER_AP];
 
     do {
         if (c1) {