[PATCH 5 of 6]

Juan Perez-Sanchez <[email protected]>
Newsgroups org.kernel.vger.linux-8086
Message-ID <CAD6VGuYwgBAowZ6-Xbg59Aqr6P8-+mcTj_60j9tUdtn+u7vMNQ@mail.gmail.com> 
Hi,

 Modified the implementation of functions find_first_non_zero_bit()
and find_first_zero_bit() in file arch/i86/lib/bitops.c to make them
faster. This came at the cost of an increase in code size. To
compensate for this, also optimized numerous functions in the
arch/i86/lib directory.

2. Code size increased by 32 bytes.

 The Image builded without errors. The kernel was tested with QEMU and
dioscuri emulators. Also in a PPro pc booting from floppy.

Greetings,

Juan
elksY.patch (application/octet-stream, 10.6 KB) 
diff -Nur elks.orig/arch/i86/lib/bitops.c elks/arch/i86/lib/bitops.c
--- elks.orig/arch/i86/lib/bitops.c	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/bitops.c	2013-02-27 18:09:39.000000000 -0600
@@ -6,19 +6,19 @@
 /*
  *	Messy as we lack atomic bit operations on an 8086.
  */
- 
+
 unsigned char clear_bit(unsigned int bit,void *addr)
 {
     register unsigned char *ptr;
     flag_t flags;
     unsigned int mask;
 
-	ptr = ((unsigned char *)addr) + (bit / 8);
-    bit %= 8;
+    ptr = ((unsigned char *)addr) + (bit >> 3);
+    bit &= 0x07;
     mask = (1 << bit);
     save_flags(flags);
     clr_irq();
-	mask &= *ptr;
+    mask &= *ptr;
     *ptr &= ~mask;
     restore_flags(flags);
     return mask >> bit;
@@ -30,12 +30,12 @@
     flag_t flags;
     unsigned int mask, r;
 
-	ptr = ((unsigned char *)addr) + (bit / 8);
-    bit %= 8;
+    ptr = ((unsigned char *)addr) + (bit >> 3);
+    bit &= 0x07;
     mask = (1 << bit);
     save_flags(flags);
     clr_irq();
-	r = *ptr & mask;
+    r = *ptr & mask;
     *ptr |= mask;
     restore_flags(flags);
     return r >> bit;
@@ -43,40 +43,56 @@
 
 unsigned char test_bit(unsigned int bit,void *addr)
 {
-	return ( ((1 << (bit % 8))
-			  & ((unsigned char *) addr)[bit / 8]) != 0);
+	return ( ((1 << (bit & 0x07))
+			  & *((unsigned char *)addr + (bit >> 3))) != 0);
 }
 
 /* Ack... nobody even seemed to try to write to a file before 0.0.49a was
  * released, or otherwise they might have tracked it down to this being
- * non-existant :) 
+ * non-existant :)
  * - Chad
  */
 
 /* Use the old faithful version */
-unsigned int find_first_non_zero_bit(void *addr, unsigned int len)
+unsigned int find_first_non_zero_bit(register int *addr, unsigned int len)
 {
-	register char *pi = 0;
+    register char *bit = 0;
+    unsigned int mask;
 
-	while (((unsigned int) pi) < len) {
-		if (test_bit(((unsigned int) pi), addr)) {
-			break;
-		}
-		++pi;
+    do {
+	if(*addr) {
+	    mask = 1;
+	    while(!(*addr & mask)) {
+		mask <<= 1;
+		bit++;
+	    }
+	    break;
 	}
-	return (unsigned int) pi;
+	addr++;
+    } while((unsigned int)(bit += 16) < len);
+    if((unsigned int)bit > len)
+	bit = (char *)len;
+    return (unsigned int)bit;
 }
 
 /* Use the old faithful version */
-unsigned int find_first_zero_bit(void *addr, unsigned int len)
+unsigned int find_first_zero_bit(register int *addr, unsigned int len)
 {
-	register char *pi = 0;
+    register char *bit = 0;
+    unsigned int mask;
 
-	while (((unsigned int) pi) < len) {
-		if (!test_bit(((unsigned int) pi), addr)) {
-			break;
-		}
-		++pi;
+    do {
+	if(~(*addr)) {
+	    mask = 1;
+	    while(*addr & mask) {
+		mask <<= 1;
+		bit++;
+	    }
+	    break;
 	}
-	return (unsigned int) pi;
+	addr++;
+    } while((unsigned int)(bit += 16) < len);
+    if((unsigned int)bit > len)
+	bit = (char *)len;
+    return (unsigned int)bit;
 }
diff -Nur elks.orig/arch/i86/lib/border.s elks/arch/i86/lib/border.s
--- elks.orig/arch/i86/lib/border.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/border.s	2013-02-27 18:09:39.000000000 -0600
@@ -7,14 +7,11 @@
 
 _htonl:
 _ntohl:
-	push	bp
-	mov	bp,sp
-	mov     bx,4[bp]
-	mov     ax,6[bp]
-	mov	cl,#8
-	ror	ax,cl
-	ror	bx,cl
-	mov	dx,bx
-	pop	bp
-	ret
+	pop	bx
+	pop	dx
+	pop	ax
+	sub	sp,#4
+	xchg	ah,al
+	xchg	dh,dl
+	jmp	bx
 
diff -Nur elks.orig/arch/i86/lib/lcmpb.s elks/arch/i86/lib/lcmpb.s
--- elks.orig/arch/i86/lib/lcmpb.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/lcmpb.s	2013-02-27 18:09:39.000000000 -0600
@@ -10,12 +10,7 @@
 
 lcmpub:
 	sub	ax,(di)		! don't need to preserve ax
-	je	LCMP_NOT_SURE
-	ret
-
-	.even
-
-LCMP_NOT_SURE:
+	jne	LCMP_EXIT
 	cmp	bx,2(di)
 	jb	LCMP_B_AND_LT	! b (below) becomes lt (less than) as well
 	jge	LCMP_EXIT	! ge and already ae
diff -Nur elks.orig/arch/i86/lib/lcmpl.s elks/arch/i86/lib/lcmpl.s
--- elks.orig/arch/i86/lib/lcmpl.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/lcmpl.s	2013-02-27 18:09:39.000000000 -0600
@@ -10,12 +10,7 @@
 
 lcmpul:
 	sub	bx,2[di]	! don't need to preserve bx
-	je	LCMP_NOT_SURE
-	ret
-
-	.even
-
-LCMP_NOT_SURE:
+	jne	LCMP_EXIT
 	cmp	ax,[di]
 	jb	LCMP_B_AND_LT	! b (below) becomes lt (less than) as well
 	jge	LCMP_EXIT	! ge and already ae
diff -Nur elks.orig/arch/i86/lib/ldecb.s elks/arch/i86/lib/ldecb.s
--- elks.orig/arch/i86/lib/ldecb.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/ldecb.s	2013-02-27 18:09:39.000000000 -0600
@@ -8,14 +8,6 @@
 ldecb:
 
 ldecub:
-	cmp	2(bx),*0
-	je	LDEC_BOTH
-	dec	2(bx)
-	ret
-
-	.even
-
-LDEC_BOTH:
-	dec	2(bx)
-	dec	(bx)
+	sub	word ptr 2[bx],#1
+	sbb	word ptr [bx],#0
 	ret
diff -Nur elks.orig/arch/i86/lib/ldecl.s elks/arch/i86/lib/ldecl.s
--- elks.orig/arch/i86/lib/ldecl.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/ldecl.s	2013-02-27 18:09:39.000000000 -0600
@@ -8,14 +8,6 @@
 ldecl:
 
 ldecul:
-	cmp	word ptr [bx],*0
-	je	LDEC_BOTH
-	dec	word ptr [bx]
-	ret
-
-	.even
-
-LDEC_BOTH:
-	dec	word ptr [bx]
-	dec	word ptr 2[bx]
+	sub	word ptr [bx],#1
+	sbb	word ptr 2[bx],#0
 	ret
diff -Nur elks.orig/arch/i86/lib/lincb.s elks/arch/i86/lib/lincb.s
--- elks.orig/arch/i86/lib/lincb.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/lincb.s	2013-02-27 18:09:39.000000000 -0600
@@ -9,11 +9,7 @@
 
 lincub:
 	inc	2(bx)
-	je	LINC_HIGH_WORD
-	ret
-
-	.even
-
-LINC_HIGH_WORD:
+	jne	LINC_END
 	inc	(bx)
+LINC_END:
 	ret
diff -Nur elks.orig/arch/i86/lib/lsrb.s elks/arch/i86/lib/lsrb.s
--- elks.orig/arch/i86/lib/lsrb.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/lsrb.s	2013-02-27 18:09:39.000000000 -0600
@@ -9,7 +9,8 @@
 	mov	cx,di
 	jcxz	LSR_EXIT
 	cmp	cx,*32
-	jae	LSR_SIGNBIT
+	jb	LSR_LOOP
+	mov	cx,*32		! equivalent to +infinity in this context
 
 LSR_LOOP:
 	sar	ax,*1
@@ -19,8 +20,3 @@
 LSR_EXIT:
 	ret
 
-	.even
-
-LSR_SIGNBIT:
-	mov	cx,*32		! equivalent to +infinity in this context
-	j	LSR_LOOP
diff -Nur elks.orig/arch/i86/lib/lsrl.s elks/arch/i86/lib/lsrl.s
--- elks.orig/arch/i86/lib/lsrl.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/lsrl.s	2013-02-27 18:09:39.000000000 -0600
@@ -9,7 +9,8 @@
 	mov	cx,di
 	jcxz	LSR_EXIT
 	cmp	cx,*32
-	jae	LSR_SIGNBIT
+	jb	LSR_LOOP
+	mov	cx,*32		! equivalent to +infinity in this context
 
 LSR_LOOP:
 	sar	bx,*1
@@ -19,8 +20,3 @@
 LSR_EXIT:
 	ret
 
-	.even
-
-LSR_SIGNBIT:
-	mov	cx,*32		! equivalent to +infinity in this context
-	j	LSR_LOOP
diff -Nur elks.orig/arch/i86/lib/ltstb.s elks/arch/i86/lib/ltstb.s
--- elks.orig/arch/i86/lib/ltstb.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/ltstb.s	2013-02-27 19:49:32.000000000 -0600
@@ -10,18 +10,9 @@
 
 ltstub:
 	test	ax,ax
-	je	LTST_NOT_SURE
-	ret
-
-	.even
-
-LTST_NOT_SURE:
+	jne	LTSTB_RET
 	test	bx,bx
-	js	LTST_FIX_SIGN
-	ret
-
-	.even
-
-LTST_FIX_SIGN:
+	jns	LTST_RET
 	inc	ax		! clear ov and mi, set ne for greater than
+LTSTB_RET:
 	ret
diff -Nur elks.orig/arch/i86/lib/ltstl.s elks/arch/i86/lib/ltstl.s
--- elks.orig/arch/i86/lib/ltstl.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/ltstl.s	2013-02-27 19:51:12.000000000 -0600
@@ -9,18 +9,9 @@
 ltstl:
 ltstul:
 	test	bx,bx
-	je	LTST_NOT_SURE
-	ret
-
-	.even
-
-LTST_NOT_SURE:
+	jne	LTSTL_RET
 	test	ax,ax
-	js	LTST_FIX_SIGN
-	ret
-
-	.even
-
-LTST_FIX_SIGN:
+	jns	LTSTL_RET
 	inc	bx		! clear ov and mi, set ne for greater than
+LTSTL_RET:
 	ret
diff -Nur elks.orig/arch/i86/lib/memmove.c elks/arch/i86/lib/memmove.c
--- elks.orig/arch/i86/lib/memmove.c	2012-10-18 13:48:54.000000000 -0500
+++ elks/arch/i86/lib/memmove.c	2013-02-27 18:50:27.000000000 -0600
@@ -20,7 +20,7 @@
 
 	if ((sseg < dseg) || ((sseg == dseg) && (soff < doff))) {
 	    --bytes;
-	    blt_forth(sseg, soff+bytes, dseg, doff+bytes, bytes+1);
+	    blt_forth(soff+bytes, sseg, doff+bytes, dseg, bytes+1);
 	} else {
 	    fmemcpy(dseg, doff, sseg, soff, bytes );
 	}
@@ -30,26 +30,20 @@
 #ifndef S_SPLINT_S
 #asm
 	.text
-				! blt_forth( sseg, soff, dseg, doff, bytes )
-				! for to > from 
+				! blt_forth( soff, sseg, doff, dseg, bytes )
+				! for to > from
 	.even
 
 _blt_forth:
 	push	bp
 	mov	bp, sp
-	push	ax
 	push	es
 	push	ds
-	push	cx	
 	push	si
 	push	di
 	pushf
-	mov	ax, [bp+4]
-	mov	ds, ax
-	mov	si, [bp+6]
-	mov	ax, [bp+8]
-	mov	es, ax
-	mov	di, [bp+10]
+	lds	si, [bp+4]
+	les	di, [bp+8]
 	mov	cx, [bp+12]
 	std
 	rep
@@ -57,10 +51,8 @@
 	popf
 	pop	di
 	pop	si
-	pop	cx
 	pop	ds
 	pop	es
-	pop	ax
 	pop	bp
 	ret
 
diff -Nur elks.orig/arch/i86/lib/string.s elks/arch/i86/lib/string.s
--- elks.orig/arch/i86/lib/string.s	2012-08-18 13:28:59.000000000 -0500
+++ elks/arch/i86/lib/string.s	2013-02-27 19:40:31.000000000 -0600
@@ -17,8 +17,6 @@
 _strlen:			! needs more testing!
 	push	bp
 	mov	bp,sp
-	push	dx
-	push	cx
 	push	di
 	mov	dx,[bp+4]
 	mov	di,dx
@@ -31,8 +29,6 @@
 	mov	ax,di
 	dec	ax
 	pop	di
-	pop	cx
-	pop	dx
 	pop	bp
 	ret
 
@@ -49,15 +45,13 @@
 	push	si
 	mov	di,[bp+4]	! address of the destination string
 	mov	si,[bp+6]	! address of the source string
-	mov	ax,di
-	push	ax		! _strcpy returns a pointer to the destination string
 	cld
 
 copyon:	lodsb			! al = [ds:si++]
 	stosb			! [es:di++] = al
 	test	al,al
 	jnz	copyon
-	pop	ax
+	mov	ax,[bp+4]	! _strcpy returns a pointer to the destination string
 	pop	si
 	pop	di
 	pop	bp
@@ -102,16 +96,13 @@
 	push	bp
 	mov	bp,sp
 	push	di
-	push	cx
 	mov	di,[bp+4]	! address of the memory block
-	push	di		! return value = start addr of block
 	mov	ax,[bp+6]	! byte to write
 	mov	cx,[bp+8]	! loop count
 	cld
 	rep			! while(cx)
 	stosb			! 	cx--, [es:di++] = al
-	pop	ax
-	pop	cx
+	mov	ax,[bp+4]	! return value = start addr of block
 	pop	di
 	pop	bp
 	ret
diff -Nur elks.orig/arch/i86/mm/user.c elks/arch/i86/mm/user.c
--- elks.orig/arch/i86/mm/user.c	2012-10-17 13:38:32.000000000 -0500
+++ elks/arch/i86/mm/user.c	2013-02-27 19:17:32.000000000 -0600
@@ -118,8 +118,7 @@
 	push	es
 	pushf
 	mov	es, 4[bp]
-	mov	di, 6[bp]
-	mov	ds, 8[bp]
+	lds	di, 6[bp]
 	mov	si, 10[bp]
 	mov	cx, 12[bp]
 	cld			! Must move upwards...
@@ -163,7 +162,6 @@
 #asm
 
 	push	di
-	push	si
 	mov	dx,es
 	mov	es,[bp+.strlen_fromfs.ds]	! source segment (local variable)
 	mov	di,[bp+.strlen_fromfs.saddr]	! source address
@@ -176,7 +174,6 @@
 	dec	di
 	mov	[bp+.strlen_fromfs.ds],di	! save in local var ds
 	mov	es,dx
-	pop	si
 	pop	di
 #endasm
 #endif
diff -Nur elks.orig/include/arch/bitops.h elks/include/arch/bitops.h
--- elks.orig/include/arch/bitops.h	2012-08-18 13:28:59.000000000 -0500
+++ elks/include/arch/bitops.h	2013-02-27 18:09:39.000000000 -0600
@@ -5,7 +5,7 @@
 extern unsigned char set_bit(unsigned int,void *);
 extern unsigned char test_bit(unsigned int,void *);
 
-extern unsigned int find_first_non_zero_bit(void *,unsigned int);
-extern unsigned int find_first_zero_bit(void *,unsigned int);
+extern unsigned int find_first_non_zero_bit(register void *,unsigned int);
+extern unsigned int find_first_zero_bit(register void *,unsigned int);
 
 #endif
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