[gccsdk] Objasm record layouts revisited

[Christopher Martin]

A month ago, I offered a tiny patch to objasm intended to allow
expressions with record layout symbols. At the time, I did not
appreciate all the issues with record layouts.

I have since revisited the code and made another attempt to resolve the
long-outstanding issues. More work is probably required, but I think
this attempt is a good start. Sorry it has taken a month to get this
far. It has been many years since I had such difficulty understanding
another's code.

I have attached a diff file and a zip archive of my modified objasm
sources from the 4.1.1 1b release. Note that my files are organised
according to RISC OS convention; I hope this is okay.
-- 
Regards, Chris.
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diff --minimal --speed-large-files -E -b -B --strip-trailing-cr -t -T -r gccsdk-riscos-tools-src-4/1/1-rel1b.objasm.c.code patched.objasm.c.code
206a207,229
> /* Addition by CPM. Probably needs more work */
> void codeValue(const Value * value)
> {
>   switch (value->Tag.t) {
>     case ValueInt: codeInt (value->ValueInt.i); break;
>     case ValueFloat: codeFloat (value->ValueFloat.f); break;
>     case ValueString: codeString (value->ValueString.len, value->ValueString.s); break;
>     case ValueBool: codeBool (value->ValueBool.b); break;
>     case ValueCode:
>       switch (value->ValueCode.c->Tag) {
>         case CodeSymbol: codePosition (value->ValueCode.c->CodeSymbol.symbol); break;
>         default: error (ErrorSerious, FALSE, "code::codeValue received a non-CodeSymbol ValueCode");
>       };
>       break;
>     case ValueLateLabel:
>       codeSymbol (value->ValueLate.late->symbol);
>       codeInt (value->ValueLate.i);
>       codeOperator (Op_add);
>       break;
>     case ValueAddr: codeInt (value->ValueAddr.i); break;
>     default: error (ErrorSerious, FALSE, "code::codeValue received a Value of unhandled type");
>   }
> }
diff --minimal --speed-large-files -E -b -B --strip-trailing-cr -t -T -r gccsdk-riscos-tools-src-4/1/1-rel1b.objasm.c.eval patched.objasm.c.eval
126c126,127
<       if (lvalue->Tag.t == ValueAddr && rvalue->Tag.t == ValueInt)
---
>       /* Modification by CPM: Allow more flexible operations with ValueAddr labels */
>       if ((lvalue->Tag.t & (ValueInt | ValueAddr)) && (rvalue->Tag.t & (ValueInt | ValueAddr)))
128c129,136
<           lvalue->ValueAddr.i += rvalue->ValueInt.i;
---
>           /* ValueInt and ValueAddr have field i in the same place */
>           lvalue->ValueInt.i += rvalue->ValueInt.i;
>           if (lvalue->Tag.t == ValueInt && rvalue->Tag.t == ValueAddr)
>             {
>               /* Transform lvalue from a ValueInt into a ValueAddr like rvalue */
>               lvalue->Tag.t = ValueAddr;
>               lvalue->ValueAddr.r = rvalue->ValueAddr.r;
>             }
129a138
>           /* Note that I have relaxed the requirement for identical base registers */
163c172,173
<       if (lvalue->Tag.t == ValueAddr && (rvalue->Tag.t & (ValueInt | ValueAddr)))
---
>       /* Modification by CPM: Allow more flexible operations with ValueAddr labels */
>       if ((lvalue->Tag.t & (ValueInt | ValueAddr)) && (rvalue->Tag.t & (ValueInt | ValueAddr)))
165,170c175,182
<           if (rvalue->Tag.t == ValueAddr &&
<               lvalue->ValueAddr.r != rvalue->ValueAddr.r)
<             return FALSE;
<           lvalue->ValueAddr.i -= rvalue->ValueInt.i;
<           if (rvalue->Tag.t == ValueAddr)
<             lvalue->Tag.t = ValueInt;
---
>           /* ValueInt and ValueAddr have field i in the same place */
>           lvalue->ValueInt.i -= rvalue->ValueInt.i;
>           if (lvalue->Tag.t == ValueInt && rvalue->Tag.t == ValueAddr)
>             {
>               /* Transform lvalue from a ValueInt into a ValueAddr like rvalue */
>               lvalue->Tag.t = ValueAddr;
>               lvalue->ValueAddr.r = rvalue->ValueAddr.r;
>             }
171a184
>           /* Note that I have relaxed the requirement for identical base registers */
diff --minimal --speed-large-files -E -b -B --strip-trailing-cr -t -T -r gccsdk-riscos-tools-src-4/1/1-rel1b.objasm.c.m_cpuctrl patched.objasm.c.m_cpuctrl
241c241
<   ir |= LHS_OP (15) | IMM_RHS;  /* pc */
---
>   ir |= LHS_OP (15) | IMM_RHS;  /* pc */  /* Note by CPM: May have to undo this later */
251c251,267
<   codePosition (areaCurrent);   /* It's relative */
---
>   /* Modification by CPM: We no longer assume PC relativity. Instead, we first look
>      at what we get by evaluating the label alone. If it turns out to be a ValueAddr
>      then we don't do the PC-relative transformation.
>   */
>   im = exprEval (ValueInt | ValueCode | ValueLateLabel | ValueAddr);
>   if (im.Tag.t == ValueAddr)
>     {
>       if (im.ValueAddr.r != 15) {ir &= ~ LHS_OP (15); ir |= LHS_OP (im.ValueAddr.r);}
>     }
>   else
>     {
>       /* Only now that we know we don't have a ValueAddr
>          do we perform the PC-relative transformation.
>       */
>       codeInit ();
>       codeValue (&im);  /* New function added to <code.c>. Probably needs more work */
>       codePosition (areaCurrent);
255a272
>     }
258c275
<     case ValueInt:
---
>     case ValueInt: case ValueAddr:  /* Exploiting the common position of field i */
diff --minimal --speed-large-files -E -b -B --strip-trailing-cr -t -T -r gccsdk-riscos-tools-src-4/1/1-rel1b.objasm.c.m_cpumem patched.objasm.c.m_cpumem
206a207,218
>       /* Modification by CPM: We no longer assume PC relativity. Instead, we first look
>          at what we get by evaluating the label alone. If it turns out to be a ValueAddr
>          then we don't do the PC-relative transformation.
>       */
>       offset = exprEval (ValueInt | ValueCode | ValueLateLabel | ValueAddr);
>       if (offset.Tag.t != ValueAddr)
>         {
>           /* Modification by CPM: Only now that we know we don't have a ValueAddr
>              do we perform the PC-relative transformation.
>           */
>           codeInit ();
>           codeValue (&offset);  /* New function added to <code.c>. Probably needs more work */
211c223,224
<       offset = exprEval (ValueInt | ValueCode | ValueLateLabel | ValueAddr);
---
>           offset = exprEval (ValueInt | ValueCode | ValueLateLabel);
>         }
diff --minimal --speed-large-files -E -b -B --strip-trailing-cr -t -T -r gccsdk-riscos-tools-src-4/1/1-rel1b.objasm.c.value patched.objasm.c.value
260c260
<     printf("(code)\n");
---
>     printf("<%d , %p> (code)\n", v->ValueCode.len, v->ValueCode.c);
263c263,269
<     printf("(late label)\n");
---
>     printf("<%d , %p: <%d , %p: <&%x , %d , %d , %.*s>>> (late label)\n",
>            v->ValueLate.i, v->ValueLate.late,
>            v->ValueLate.late->factor, v->ValueLate.late->symbol,
>            v->ValueLate.late->symbol->type, v->ValueLate.late->symbol->declared, v->ValueLate.late->symbol->used,
>            v->ValueLate.late->symbol->len, v->ValueLate.late->symbol->str);
>     printf("\t");
>     valuePrint(&v->ValueLate.late->symbol->value);
266c272
<     printf("(addr)\n");
---
>     printf("<r%d,#%d> (addr)\n", v->ValueAddr.r, v->ValueAddr.i);
diff --minimal --speed-large-files -E -b -B --strip-trailing-cr -t -T -r gccsdk-riscos-tools-src-4/1/1-rel1b.objasm.h.code patched.objasm.h.code
71a72,74
> /* Addition by CPM. Probably needs more work */
> void codeValue(const Value * value);
>
diff --minimal --speed-large-files -E -b -B --strip-trailing-cr -t -T -r gccsdk-riscos-tools-src-4/1/1-rel1b.objasm.h.value patched.objasm.h.value
124a125,127
> #else
> /* Modification by CPM: Allows valuePrint calls to not need DEBUG wrapping */
> #define valuePrint(v)
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