[PATCH v3 9/9] sm501: Fix and optimize overlap check

* [PATCH v3 9/9] sm501: Fix and optimize overlap check
  2020-06-20 20:56 [PATCH v3 0/9] More sm501 fixes and optimisations BALATON Zoltan
                   ` (2 preceding siblings ...)
  2020-06-20 20:56 ` [PATCH v3 1/9] sm501: Fix bounds checks BALATON Zoltan
@ 2020-06-20 20:56 ` BALATON Zoltan
  2020-06-22 19:38   ` Peter Maydell
  2020-06-24 16:42   ` [PATCH v4] " BALATON Zoltan
  2020-06-20 20:56 ` [PATCH v3 3/9] sm501: Ignore no-op blits BALATON Zoltan
                   ` (4 subsequent siblings)
  8 siblings, 2 replies; 15+ messages in thread
From: BALATON Zoltan @ 2020-06-20 20:56 UTC (permalink / raw)
  To: qemu-devel
  Cc: Peter Maydell, Sebastian Bauer, Magnus Damm, Gerd Hoffmann,
	Aurelien Jarno

When doing reverse blit we need to check if source and dest overlap
but it is not trivial due to possible different base and pitch of
source and dest. Do rectangle overlap if base and pitch match,
otherwise just check if memory area containing the rects overlaps so
rects could possibly overlap.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/display/sm501.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/hw/display/sm501.c b/hw/display/sm501.c
index 2db347dcbc..e7c69bf7fd 100644
--- a/hw/display/sm501.c
+++ b/hw/display/sm501.c
@@ -690,6 +690,7 @@ static void sm501_2d_operation(SM501State *s)
     unsigned int dst_pitch = (s->twoD_pitch >> 16) & 0x1FFF;
     int crt = (s->dc_crt_control & SM501_DC_CRT_CONTROL_SEL) ? 1 : 0;
     int fb_len = get_width(s, crt) * get_height(s, crt) * get_bpp(s, crt);
+    bool overlap = false;
 
     if ((s->twoD_stretch >> 16) & 0xF) {
         qemu_log_mask(LOG_UNIMP, "sm501: only XY addressing is supported.\n");
@@ -784,16 +785,21 @@ static void sm501_2d_operation(SM501State *s)
                          ldn_he_p(&s->local_mem[src_base + si], bypp));
                 break;
             }
-            /* Check for overlaps, this could be made more exact */
-            uint32_t sb, se, db, de;
-            sb = src_base + src_x + src_y * (width + src_pitch);
-            se = sb + width + height * (width + src_pitch);
-            db = dst_base + dst_x + dst_y * (width + dst_pitch);
-            de = db + width + height * (width + dst_pitch);
-            if (rtl && ((db >= sb && db <= se) || (de >= sb && de <= se))) {
-                /* regions may overlap: copy via temporary */
-                int llb = width * bypp;
-                int tmp_stride = DIV_ROUND_UP(llb, sizeof(uint32_t));
+            /* If reverse blit do simple check for overlaps */
+            if (rtl && src_base == dst_base && src_pitch == dst_pitch) {
+                overlap = (src_x < dst_x + width && src_x + width > dst_x &&
+                           src_y < dst_y + height && src_y + height > dst_y);
+            } else if (rtl) {
+                unsigned int sb, se, db, de;
+                sb = src_base + (src_x + src_y * src_pitch) * bypp;
+                se = sb + (width + height * src_pitch) * bypp;
+                db = dst_base + (dst_x + dst_y * dst_pitch) * bypp;
+                de = db + (width + height * dst_pitch) * bypp;
+                overlap = (db >= sb && db <= se) || (de >= sb && de <= se);
+            }
+            if (overlap) {
+                /* pixman can't do reverse blit: copy via temporary */
+                int tmp_stride = DIV_ROUND_UP(width * bypp, sizeof(uint32_t));
                 uint32_t *tmp = tmp_buf;
 
                 if (tmp_stride * sizeof(uint32_t) * height > sizeof(tmp_buf)) {
-- 
2.21.3



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