DynASM: Fix global label references

ARM64 patch contributed by Hao Sun and Nick Gasson.

dynasm/dasm_arm.h

@@ -294,7 +294,7 @@ int dasm_link(Dst_DECL, size_t *szp)
 
   { /* Handle globals not defined in this translation unit. */
     int idx;
-    for (idx = 20; idx*sizeof(int) < D->lgsize; idx++) {
+    for (idx = 10; idx*sizeof(int) < D->lgsize; idx++) {
       int n = D->lglabels[idx];
       /* Undefined label: Collapse rel chain and replace with marker (< 0). */
       while (n > 0) { int *pb = DASM_POS2PTR(D, n); n = *pb; *pb = -idx; }
@@ -371,7 +371,10 @@ int dasm_encode(Dst_DECL, void *buffer)
 	  ins &= 255; while ((((char *)cp - base) & ins)) *cp++ = 0xe1a00000;
 	  break;
 	case DASM_REL_LG:
-	  CK(n >= 0, UNDEF_LG);
+	  if (n < 0) {
+	    n = (int)((ptrdiff_t)D->globals[-n] - (ptrdiff_t)cp - 4);
+	    goto patchrel;
+	  }
 	  /* fallthrough */
 	case DASM_REL_PC:
 	  CK(n >= 0, UNDEF_PC);

dynasm/dasm_arm64.h

@@ -354,7 +354,7 @@ int dasm_link(Dst_DECL, size_t *szp)
 
   { /* Handle globals not defined in this translation unit. */
     int idx;
-    for (idx = 20; idx*sizeof(int) < D->lgsize; idx++) {
+    for (idx = 10; idx*sizeof(int) < D->lgsize; idx++) {
       int n = D->lglabels[idx];
       /* Undefined label: Collapse rel chain and replace with marker (< 0). */
       while (n > 0) { int *pb = DASM_POS2PTR(D, n); n = *pb; *pb = -idx; }
@@ -432,7 +432,10 @@ int dasm_encode(Dst_DECL, void *buffer)
 	  ins &= 255; while ((((char *)cp - base) & ins)) *cp++ = 0xe1a00000;
 	  break;
 	case DASM_REL_LG:
-	  CK(n >= 0, UNDEF_LG);
+	  if (n < 0) {
+	    n = (int)((ptrdiff_t)D->globals[-n] - (ptrdiff_t)cp + 4);
+	    goto patchrel;
+	  }
 	  /* fallthrough */
 	case DASM_REL_PC:
 	  CK(n >= 0, UNDEF_PC);

dynasm/dasm_mips.h

@@ -273,7 +273,7 @@ int dasm_link(Dst_DECL, size_t *szp)
 
   { /* Handle globals not defined in this translation unit. */
     int idx;
-    for (idx = 20; idx*sizeof(int) < D->lgsize; idx++) {
+    for (idx = 10; idx*sizeof(int) < D->lgsize; idx++) {
       int n = D->lglabels[idx];
       /* Undefined label: Collapse rel chain and replace with marker (< 0). */
       while (n > 0) { int *pb = DASM_POS2PTR(D, n); n = *pb; *pb = -idx; }
@@ -349,7 +349,10 @@ int dasm_encode(Dst_DECL, void *buffer)
 	  ins &= 255; while ((((char *)cp - base) & ins)) *cp++ = 0x60000000;
 	  break;
 	case DASM_REL_LG:
-	  CK(n >= 0, UNDEF_LG);
+	  if (n < 0) {
+	    n = (int)((ptrdiff_t)D->globals[-n] - (ptrdiff_t)cp);
+	    goto patchrel;
+	  }
 	  /* fallthrough */
 	case DASM_REL_PC:
 	  CK(n >= 0, UNDEF_PC);

dynasm/dasm_ppc.h

@@ -277,7 +277,7 @@ int dasm_link(Dst_DECL, size_t *szp)
 
   { /* Handle globals not defined in this translation unit. */
     int idx;
-    for (idx = 20; idx*sizeof(int) < D->lgsize; idx++) {
+    for (idx = 10; idx*sizeof(int) < D->lgsize; idx++) {
       int n = D->lglabels[idx];
       /* Undefined label: Collapse rel chain and replace with marker (< 0). */
       while (n > 0) { int *pb = DASM_POS2PTR(D, n); n = *pb; *pb = -idx; }
@@ -353,7 +353,10 @@ int dasm_encode(Dst_DECL, void *buffer)
 	  ins &= 255; while ((((char *)cp - base) & ins)) *cp++ = 0x60000000;
 	  break;
 	case DASM_REL_LG:
-	  CK(n >= 0, UNDEF_LG);
+	  if (n < 0) {
+	    n = (int)((ptrdiff_t)D->globals[-n] - (ptrdiff_t)cp);
+	    goto patchrel;
+	  }
 	  /* fallthrough */
 	case DASM_REL_PC:
 	  CK(n >= 0, UNDEF_PC);