Added DSM directive for 56001 mode (and not only). Updated doc. Condensed usage message.

[rmac] / direct.c

diff --git a/direct.c b/direct.c
index 0c8dfb5b0fba563a5081a800c4cf64df83bb57f1..5628ef90f8226d59d064e0e9757634c3ac3d6852 100644 (file)
--- a/direct.c
+++ b/direct.c
@@ -51,6 +51,7 @@ int d_abs(void);
 int d_comm(void);
 int d_dc(WORD);
 int d_ds(WORD);
+int d_dsm(WORD);
 int d_dcb(WORD);
 int d_globl(void);
 int d_gpu(void);
@@ -153,6 +154,7 @@ int (*dirtab[])() = {
        d_nofpu,                        // 65 nofpu
        d_opt,                          // 66 .opt
        d_objproc,                      // 67 .objproc
+       d_dsm,                          // 68 .dsm
 };
 
 
@@ -1127,6 +1129,51 @@ int d_ds(WORD siz)
 }
 
 
+//
+// dsm[.siz] expression
+// Define modulo storage
+// Quoting the Motorola assembler manual:
+// "The DSM directive reserves a block of memory the length of which in words is equal to
+// the value of <expression>.If the runtime location counter is not zero, this directive first
+// advances the runtime location counter to a base address that is a multiple of 2k, where
+// 2k >= <expression>."
+// The kicker of course is written a few sentences after:
+// "<label>, if present, will be assigned the value of the runtime location counter after a valid
+// base address has been established."
+//
+int d_dsm(WORD siz)
+{
+       TOKEN * tok_current = tok;  // Keep track of where tok was when we entered this procedure
+       uint64_t eval;
+
+       if (abs_expr(&eval) != OK)
+               return 0;
+
+       // Round up to the next highest power of 2
+       // Nicked from https://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
+       eval--;
+       eval |= eval >> 1;
+       eval |= eval >> 2;
+       eval |= eval >> 4;
+       eval |= eval >> 8;
+       eval |= eval >> 16;
+
+       int units_to_skip;
+       units_to_skip = eval + 1 - sloc;
+       sloc += units_to_skip;          // Bump up sloc - TODO: check if this goes over the RAM limits?
+
+       // If a label has been defined in the same line as dsm, its value also needs to be adjusted
+       if (label_defined)
+       {
+               SYM * label = lookup(label_defined, LABEL, 0);
+               label->svalue += units_to_skip;
+       }
+
+       tok = tok_current;              // Rewind tok back to where it was
+       return d_ds(siz);               // And let d_ds take over from here
+}
+
+
 //
 // dc.b, dc.w / dc, dc.l, dc.i, dc.q, dc.d, dc.s, dc.x
 //