Allow JR between sections

Previously, JR was only allowed if the destination label was in the same
section as the JR. This patch removes this restriction. The check to see
if the relative value overflows is now done when linking the ROM.

Signed-off-by: Antonio Niño Díaz <antonio_nd@outlook.com>

docs/rgbds.5.html

@@ -121,6 +121,7 @@ REPT NumberOfSections
             BYTE    Type         ; 0 = BYTE patch. 
                                  ; 1 = little endian WORD patch. 
                                  ; 2 = little endian LONG patch. 
+                                 ; 3 = JR offset value BYTE patch. 
  
             LONG    RPNSize      ; Size of the buffer with the RPN. 
                                  ; expression. 

include/linkdefs.h

@@ -66,7 +66,8 @@ enum eSymbolType {
 enum ePatchType {
 	PATCH_BYTE	= 0x00,
 	PATCH_WORD_L	= 0x01,
-	PATCH_LONG_L	= 0x02
+	PATCH_LONG_L	= 0x02,
+	PATCH_BYTE_JR	= 0x03
 };
 
 #endif /* RGBDS_LINKDEFS_H */

src/asm/asmy.y

@@ -455,7 +455,6 @@ static void updateUnion(void)
 %type	<nConstValue>	const_3bit
 %type	<sVal>		const_8bit
 %type	<sVal>		const_16bit
-%type	<sVal>		const_PCrel
 %type	<nConstValue>	sectiontype
 
 %type	<tzString>	string
@@ -1116,14 +1115,6 @@ constlist_32bit_entry_single : /* empty */
 		}
 ;
 
-const_PCrel	: relocconst
-		{
-			if (!rpn_isPCRelative(&$1))
-				yyerror("Expression must be PC-relative");
-			$$ = $1;
-		}
-;
-
 const_8bit	: relocconst
 		{
 			if( (!rpn_isReloc(&$1)) && (($1.nVal < -128) || ($1.nVal > 255)) )
@@ -1612,12 +1603,12 @@ z80_jp		: T_Z80_JP const_16bit
 		}
 ;
 
-z80_jr		: T_Z80_JR const_PCrel
+z80_jr		: T_Z80_JR const_16bit
 		{
 			out_AbsByte(0x18);
 			out_PCRelByte(&$2);
 		}
-		| T_Z80_JR ccode comma const_PCrel
+		| T_Z80_JR ccode comma const_16bit
 		{
 			out_AbsByte(0x20 | ($2 << 3));
 			out_PCRelByte(&$4);

src/asm/output.c

@@ -875,19 +875,31 @@ void out_RelLong(struct Expression *expr)
 }
 
 /*
- * Output a PC-relative byte
+ * Output a PC-relative relocatable byte. Checking will be done to see if it
+ * is an absolute value in disguise.
  */
 void out_PCRelByte(struct Expression *expr)
 {
-	int32_t b = expr->nVal;
-
 	checkcodesection();
 	checksectionoverflow(1);
-	b = (b & 0xFFFF) - (nPC + 1);
-	if (nPass == 2 && (b < -128 || b > 127))
+	if (rpn_isReloc(expr)) {
+		if (nPass == 2) {
+			pCurrentSection->tData[nPC] = 0;
+			createpatch(PATCH_BYTE_JR, expr);
+		}
+		pCurrentSection->nPC += 1;
+		nPC += 1;
+		pPCSymbol->nValue += 1;
+	} else {
+		int32_t b = expr->nVal;
+
+		b = (int16_t)((b & 0xFFFF) - (nPC + 1));
+
+		if (nPass == 2 && ((b < -128) || (b > 127)))
 			yyerror("PC-relative value must be 8-bit");
 
-	out_AbsByte(b);
+		out_AbsByte(b & 0xFF);
+	}
 	rpn_Reset(expr);
 }
 

src/link/patch.c

@@ -267,6 +267,7 @@ void Patch(void)
 		pPatch = pSect->pPatches;
 		while (pPatch) {
 			int32_t t;
+			int32_t nPatchOrg;
 
 			nPC = pSect->nOrg + pPatch->nOffset;
 			t = calcrpn(pPatch);
@@ -306,6 +307,24 @@ void Patch(void)
 				pSect->pData[pPatch->nOffset + 3] =
 					(t >> 24) & 0xFF;
 				break;
+			case PATCH_BYTE_JR:
+				/* Calculate absolute address of the patch */
+				nPatchOrg = pSect->nOrg + pPatch->nOffset;
+
+				/* t contains the destination of the jump */
+				t = (int16_t)((t & 0xFFFF) - (nPatchOrg + 1));
+
+				if (t >= -128 && t <= 255) {
+					t &= 0xFF;
+					pSect->pData[pPatch->nOffset] =
+						(uint8_t)t;
+				} else {
+					errx(1,
+					     "%s(%ld) : Value must be 8-bit",
+					     pPatch->pzFilename,
+					     pPatch->nLineNo);
+				}
+				break;
 			}
 
 			pPatch = pPatch->pNext;

src/rgbds.5

@@ -113,6 +113,7 @@ REPT NumberOfSections
             BYTE    Type         ; 0 = BYTE patch.
                                  ; 1 = little endian WORD patch.
                                  ; 2 = little endian LONG patch.
+                                 ; 3 = JR offset value BYTE patch.
 
             LONG    RPNSize      ; Size of the buffer with the RPN.
                                  ; expression.