Implement LOAD UNION and LOAD FRAGMENT

Fix #632

include/asm/section.h

@@ -43,7 +43,8 @@ void out_NewSection(char const *name, uint32_t secttype, uint32_t org,
 		    struct SectionSpec const *attributes,
 		    enum SectionModifier mod);
 void out_SetLoadSection(char const *name, uint32_t secttype, uint32_t org,
-			struct SectionSpec const *attributes);
+			struct SectionSpec const *attributes,
+			enum SectionModifier mod);
 void out_EndLoadSection(void);
 
 struct Section *sect_GetSymbolSection(void);

src/asm/parser.y

@@ -853,8 +853,8 @@ shift		: T_POP_SHIFT		{ macro_ShiftCurrentArgs(1); }
 		| T_POP_SHIFT const	{ macro_ShiftCurrentArgs($2); }
 ;
 
-load		: T_POP_LOAD string T_COMMA sectiontype sectorg sectattrs {
-			out_SetLoadSection($2, $4, $5, &$6);
+load		: T_POP_LOAD sectmod string T_COMMA sectiontype sectorg sectattrs {
+			out_SetLoadSection($3, $5, $6, &$7, $2);
 		}
 		| T_POP_ENDL	{ out_EndLoadSection(); }
 ;

src/asm/rgbasm.5

@@ -719,6 +719,13 @@ The former is situated in ROM, where the code is stored, the latter in RAM, wher
 You cannot nest
 .Ic LOAD
 blocks, nor can you change the current section within them.
+.Pp
+.Ic LOAD
+blocks can use the
+.Ic UNION
+or
+.Ic FRAGMENT
+modifiers, as described below.
 .Ss Unionized Sections
 When you're tight on RAM, you may want to define overlapping blocks of variables, as explained in the
 .Sx Unions

src/asm/section.c

@@ -30,7 +30,7 @@ struct SectionStackEntry {
 struct SectionStackEntry *sectionStack;
 uint32_t curOffset; /* Offset into the current section (see sect_GetSymbolOffset) */
 static struct Section *currentLoadSection = NULL;
-uint32_t loadOffset; /* The offset of the LOAD section within its parent */
+int32_t loadOffset; /* Offset into the LOAD section's parent (see sect_GetOutputOffset) */
 
 struct UnionStackEntry {
 	uint32_t start;
@@ -387,7 +387,8 @@ void out_NewSection(char const *name, uint32_t type, uint32_t org,
  * Set the current section by name and type
  */
 void out_SetLoadSection(char const *name, uint32_t type, uint32_t org,
-			struct SectionSpec const *attribs)
+			struct SectionSpec const *attribs,
+			enum SectionModifier mod)
 {
 	checkcodesection();
 
@@ -397,11 +398,11 @@ void out_SetLoadSection(char const *name, uint32_t type, uint32_t org,
 	if (sect_HasData(type))
 		error("`LOAD` blocks cannot create a ROM section\n");
 
-	struct Section *sect = getSection(name, type, org, attribs, false);
+	struct Section *sect = getSection(name, type, org, attribs, mod);
 
-	loadOffset = curOffset;
-	curOffset = 0; /* curOffset -= loadOffset; */
 	changeSection();
+	loadOffset = curOffset - (mod == SECTION_UNION ? 0 : sect->size);
+	curOffset -= loadOffset;
 	currentLoadSection = sect;
 }
 
@@ -409,11 +410,11 @@ void out_EndLoadSection(void)
 {
 	if (!currentLoadSection)
 		error("Found `ENDL` outside of a `LOAD` block\n");
-	currentLoadSection = NULL;
 
 	changeSection();
 	curOffset += loadOffset;
 	loadOffset = 0;
+	currentLoadSection = NULL;
 }
 
 struct Section *sect_GetSymbolSection(void)

test/asm/load-fragment.asm

@@ -0,0 +1,29 @@
+SECTION "A", ROM0
+AData::
+LOAD FRAGMENT "RAM", WRAM0
+AMem::
+	db 0, 1, 2
+AMemEnd::
+ENDL
+ADataEnd::
+	dw AMem
+
+SECTION "B", ROM0
+BData::
+LOAD FRAGMENT "RAM", WRAM0
+BMem::
+	db 3, 4, 5, 6, 7
+BMemEnd::
+ENDL
+BDataEnd::
+	dw BMem
+
+SECTION "C", ROM0
+CData::
+LOAD FRAGMENT "RAM", WRAM0
+CMem::
+	db 8, 9
+CMemEnd::
+ENDL
+CDataEnd::
+	dw CMem

test/asm/load-union.asm

@@ -0,0 +1,29 @@
+SECTION "A", ROM0
+AData::
+LOAD UNION "RAM", WRAM0
+AMem::
+	db 0, 1, 2
+AMemEnd::
+ENDL
+ADataEnd::
+	dw AMem
+
+SECTION "B", ROM0
+BData::
+LOAD UNION "RAM", WRAM0
+BMem::
+	db 3, 4, 5, 6, 7
+BMemEnd::
+ENDL
+BDataEnd::
+	dw BMem
+
+SECTION "C", ROM0
+CData::
+LOAD UNION "RAM", WRAM0
+CMem::
+	db 8, 9
+CMemEnd::
+ENDL
+CDataEnd::
+	dw CMem