Rewrite _hadd in assembler (a huge speedup!) and integrate it with free

for even faster code. The old _hadd function is now also written in
assembler but does only setup variables and calls the internal function
that is part of free.


git-svn-id: svn://svn.cc65.org/cc65/trunk@182 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/common/_hadd.s

@@ -0,0 +1,59 @@
+;
+; Ullrich von Bassewitz, 21.7.2000
+;
+; Add a block to the heap free list
+;
+; void __fastcall__ _hadd (void* mem, size_t size);
+;
+;
+
+	.importzp    	ptr1, ptr2
+	.import	       	popax
+	.import		hadd
+       	.export	     	_hadd
+
+       	.macpack	generic
+
+; Offsets into struct freeblock and other constant stuff
+
+size		= 0
+next		= 2
+prev		= 4
+admin_space	= 2
+min_size	= 6
+
+
+; Code
+
+_hadd:	sta	ptr1	    	; Store size in ptr1
+	stx	ptr1+1
+	jsr	popax		; Get the block pointer
+       	sta    	ptr2
+	stx	ptr2+1		; Store block pointer in ptr2
+
+; Check if size is greater or equal than min_size. Otherwise we don't care
+; about the block (this may only happen for user supplied blocks, blocks
+; from the heap are always large enough to hold a freeblock structure).
+
+	lda	ptr1		; Load low byte
+	ldx	ptr1+1		; Load/check high byte
+	bne	@L1
+	cmp	#min_size
+	bcs   	@L1
+
+	rts	    		; Block not large enough
+
+; The block is large enough. Set the size field in the block.
+
+@L1:	ldy	#size
+    	sta	(ptr2),y
+	iny
+	txa
+	sta	(ptr2),y
+
+; Call the internal function since variables are now setup correctly
+
+	jmp	hadd
+
+
+