From 393f31cc43cd9dff55a92e615ca52209b79944ac Mon Sep 17 00:00:00 2001
From: Jens Arnold <amiconn@rockbox.org>
Date: Tue, 18 Jul 2006 00:04:43 +0000
Subject: 1bit and 2bit LCD drivers: Low-level bit handling optimisations.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@10225 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/drivers/lcd-h100.c | 39 ++++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)

(limited to 'firmware/drivers/lcd-h100.c')

diff --git a/firmware/drivers/lcd-h100.c b/firmware/drivers/lcd-h100.c
index 42bf13a888..f460165534 100644
--- a/firmware/drivers/lcd-h100.c
+++ b/firmware/drivers/lcd-h100.c
@@ -397,24 +397,29 @@ static void bgblock(unsigned char *address, unsigned mask, unsigned bits)
                     ICODE_ATTR;
 static void bgblock(unsigned char *address, unsigned mask, unsigned bits)
 {
-    mask &= ~bits;
-    *address = (*address & ~mask) | (bg_pattern & mask);
+    unsigned data = *address;
+
+    *address = data ^ ((data ^ bg_pattern) & mask & ~bits);
 }
 
 static void fgblock(unsigned char *address, unsigned mask, unsigned bits)
                     ICODE_ATTR;
 static void fgblock(unsigned char *address, unsigned mask, unsigned bits)
 {
-    mask &= bits;
-    *address = (*address & ~mask) | (fg_pattern & mask);
+    unsigned data = *address;
+
+    *address = data ^ ((data ^ fg_pattern) & mask & bits);
 }
 
 static void solidblock(unsigned char *address, unsigned mask, unsigned bits)
                        ICODE_ATTR;
 static void solidblock(unsigned char *address, unsigned mask, unsigned bits)
 {
-    *address = (*address & ~mask) | (bits & mask & fg_pattern)
-                                  | (~bits & mask & bg_pattern);
+    unsigned data = *address;
+    unsigned bgp  = bg_pattern;
+    
+    bits     = bgp  ^ ((bgp ^ fg_pattern) & bits);
+    *address = data ^ ((data ^ bits) & mask);
 }
 
 static void flipinvblock(unsigned char *address, unsigned mask, unsigned bits)
@@ -428,24 +433,29 @@ static void bginvblock(unsigned char *address, unsigned mask, unsigned bits)
                        ICODE_ATTR;
 static void bginvblock(unsigned char *address, unsigned mask, unsigned bits)
 {
-    mask &= bits;
-    *address = (*address & ~mask) | (bg_pattern & mask);
+    unsigned data = *address;
+
+    *address = data ^ ((data ^ bg_pattern) & mask & bits);
 }
 
 static void fginvblock(unsigned char *address, unsigned mask, unsigned bits)
                        ICODE_ATTR;
 static void fginvblock(unsigned char *address, unsigned mask, unsigned bits)
 {
-    mask &= ~bits;
-    *address = (*address & ~mask) | (fg_pattern & mask);
+    unsigned data = *address;
+
+    *address = data ^ ((data ^ fg_pattern) & mask & ~bits);
 }
 
 static void solidinvblock(unsigned char *address, unsigned mask, unsigned bits)
                           ICODE_ATTR;
 static void solidinvblock(unsigned char *address, unsigned mask, unsigned bits)
 {
-    *address = (*address & ~mask) | (~bits & mask & fg_pattern)
-                                  | (bits & mask & bg_pattern);
+    unsigned data = *address;
+    unsigned fgp  = fg_pattern;
+    
+    bits     = fgp  ^ ((fgp ^ bg_pattern) & bits);
+    *address = data ^ ((data ^ bits) & mask);
 }
 
 lcd_blockfunc_type* const lcd_blockfuncs[8] = {
@@ -455,7 +465,10 @@ lcd_blockfunc_type* const lcd_blockfuncs[8] = {
 
 static inline void setblock(unsigned char *address, unsigned mask, unsigned bits)
 {
-    *address = (*address & ~mask) | (bits & mask);
+    unsigned data = *address;
+
+    bits    ^= data;
+    *address = data ^ (bits & mask);
 }
 
 /*** drawing functions ***/
-- 
cgit v1.2.3