optimization in variable search

src/basic/engine_editor/find_line_46K_50K.s

@@ -25,7 +25,7 @@ find_line_from_current:
 
 	// Check if line is not empty
 
-	jsr find_line_null_ptr_check       // we can't use 'is_line_pointer_null', it maps out/in the BASIC ROM
+	jsr line_pointer_null_check        // we can't use 'is_line_pointer_null', it maps out/in the BASIC ROM
 	beq remap_BASIC_sec_rts            // search failed if there is no program
 
 	// Fetch the high byte of line number and compare
@@ -52,7 +52,7 @@ find_line_next:
 
 	// Advance to the next line
 
-	jsr find_line_null_ptr_check       // we can't use 'is_line_pointer_null', it maps out/in the BASIC ROM
+	jsr line_pointer_null_check        // we can't use 'is_line_pointer_null', it maps out/in the BASIC ROM
 	beq remap_BASIC_sec_rts            // search failed if no more line exists
 
 	ldy #$00
@@ -68,7 +68,7 @@ find_line_next:
 
 	jmp_8 find_line_from_current
 
-find_line_null_ptr_check:
+line_pointer_null_check:               // reused by 'is_line_pointer_null'
 
 	// Check the pointer
 
@@ -82,7 +82,6 @@ find_line_null_ptr_check:
 !:
 	rts
 
-
 remap_BASIC_clc_rts:
 
 	lda #$27

src/basic/engine_runtime/is_line_pointer_null_46K_50K.s

@@ -16,15 +16,9 @@ is_line_pointer_null:
 	lda #$26
 	sta CPU_R6510
 
-	// Check the pointer
+	// Check the pointer - reuse code from other routine
 
-	ldy #$01                 // for non-NULL pointer, high byte is almost certainly not NULL
-	lda (OLDTXT),y
-	bne !+                   // branch if pointer not NULL
-	
-	dey
-	lda (OLDTXT),y
-!:
+	jsr line_pointer_null_check
 
 	// Restore memory mapping and quit
 
@@ -32,6 +26,7 @@ is_line_pointer_null:
 	lda #$27
 	sta CPU_R6510
 	plp
+
 	rts
 
 #endif

src/basic/engine_variables/fetch_variable.s

@@ -130,13 +130,15 @@ fetch_variable_find_addr_loop:
 	// Compare current variable name with searched one
 	// XXX consider creating optimized version for 46K/50K memory models
 
+#if CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	jsr helper_cmp_varnam
+#else
+
 	ldy #$00
 
 #if CONFIG_MEMORY_MODEL_60K
 	ldx #<VARPNT
 	jsr peek_under_roms
-#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	jsr peek_under_roms_via_VARPNT
 #else // CONFIG_MEMORY_MODEL_38K
 	lda (VARPNT),y
 #endif
@@ -148,13 +150,14 @@ fetch_variable_find_addr_loop:
 
 #if CONFIG_MEMORY_MODEL_60K
 	jsr peek_under_roms
-#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	jsr peek_under_roms_via_VARPNT
 #else // CONFIG_MEMORY_MODEL_38K
 	lda (VARPNT),y
 #endif
 
 	cmp VARNAM+1
+
+#endif
+
 	bne fetch_variable_find_addr_next
 
 	// FALLTROUGH

src/basic/engine_variables/helper_cmp_varnam_46K_50K.s

@@ -0,0 +1,38 @@
+// #LAYOUT# STD *       #TAKE-HIGH
+// #LAYOUT# *   BASIC_0 #TAKE-HIGH
+// #LAYOUT# *   *       #IGNORE
+
+// This has to go $E000 or above - routines below banks out the main BASIC ROM!
+
+#if CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+
+helper_cmp_varnam:
+
+	// Unmap BASIC lower ROM
+
+	lda #$26
+	sta CPU_R6510
+
+	// Compare variable name
+
+	ldy #$00
+	lda (VARPNT),y
+
+	cmp VARNAM+0
+	bne !+
+
+	iny
+	lda (VARPNT),y
+	cmp VARNAM+1
+!:
+	// Restore default memory mapping
+	// XXX consider deduplicating with 'is_line_pointer_null'
+
+	php
+	lda #$27
+	sta CPU_R6510
+	plp
+
+	rts
+
+#endif

src/basic/engine_variables/helper_strdesccpy_46K_50K.s

@@ -2,7 +2,7 @@
 // #LAYOUT# *   BASIC_0 #TAKE-HIGH
 // #LAYOUT# *   *       #IGNORE
 
-// This has to go $E000 or above - routines below banks out the main BASIC ROM!
+// This has to go $E000 or above - routine below banks out the main BASIC ROM!
 
 //
 // Helper routine to copy string descriptor