Avoid out-of-range branches around asm code using dcl directives.

The branch range calculation treated dcl directives as taking 2 bytes rather than 4, which could result in out-of-range branches. These could result in linker errors (for forward branches) or silently generating wrong code (for backward branches).

This patch now treats dcb, dcw, and dcl as separate directives in the native-code layer, so the appropriate length can be calculated for each.

Here is an example of code affected by this:

int main(int argc, char **argv) {
top:
        if (!argc) { /* this caused a linker error */
                asm {
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                        dcl 0
                }
                goto top; /* this generated bad code with no error */
        }
}

Asm.pas

@@ -568,13 +568,18 @@ while not (token.kind in [rbracech,eofsy]) do begin
    {handle data declarations}
    else if opc <= o_dcl then begin
       Exp([semicolonch], true);
-      code^.s := d_add;
-      if opc = o_dcb then
-         code^.r := ord(direct)
-      else if opc = o_dcw then
-         code^.r := ord(absolute)
-      else
+      if opc = o_dcb then begin
+         code^.s := d_dcb;
+         code^.r := ord(direct);
+         end {if}
+      else if opc = o_dcw then begin
+         code^.s := d_dcw;
+         code^.r := ord(absolute);
+         end {else if}
+      else begin
+         code^.s := d_dcl;
          code^.r := ord(longabsolute);
+         end; {else}
       end {if opc <= o_dcl}
 
    {handle the brk instruction}

CGI.pas

@@ -205,8 +205,11 @@ const
    d_wrd                  =    261;
    d_sym                  =    262;
    d_cns                  =    263;
+   d_dcb                  =    264;
+   d_dcw                  =    265;
+   d_dcl                  =    266;
 
-   max_opcode             =    263;
+   max_opcode             =    266;
    
    asmFlag                =  $8000;     {or'd with opcode to indicate asm code}
 

Native.asm

@@ -164,5 +164,5 @@ size     dc    i1'2,2,2,2,2,2,2,2,1,3,1,1,3,3,3,4'
          dc    i1'3,2,2,2,2,2,2,2,1,3,1,1,3,3,3,4'
          dc    i1'2,2,2,2,3,2,2,2,1,3,1,1,3,3,3,4'
 
-         dc    i1'0,0,1,2,0,2,0,255'
+         dc    i1'0,0,1,2,0,2,0,255,1,2,4'
          end

Native.pas

@@ -545,7 +545,7 @@ case mode of
       end;
 
    longabsolute: begin
-      if opcode <> d_add then begin
+      if opcode <> d_dcl then begin
          CnOut(opcode);
          i := 3;
          end {if}
@@ -556,7 +556,7 @@ case mode of
       else if (flags & constantOpnd) <> 0 then begin
          lval := ord4(name);
          CnOut2(long(lval).lsw);
-         if opcode = d_add then
+         if opcode = d_dcl then
             CnOut2(long(lval).msw)
          else
             CnOut(long(lval).msw);
@@ -566,13 +566,13 @@ case mode of
       else begin
          CnOut2(operand);
          CnOut(0);
-         if opcode = d_add then
+         if opcode = d_dcl then
             CnOut(0);
          end; {else}
       end;
 
    absolute: begin
-      if opcode <> d_add then
+      if opcode <> d_dcw then
          CnOut(opcode);
       if (flags & localLab) <> 0 then
          LabelSearch(long(name).lsw, 2, 0, operand)
@@ -585,7 +585,7 @@ case mode of
       end;
 
    direct: begin
-      if opcode <> d_add then
+      if opcode <> d_dcb then
          CnOut(opcode);
       if (flags & localLab) <> 0 then
          LabelSearch(long(name).lsw, 1, 0, operand)

cc.notes

@@ -1907,6 +1907,8 @@ int foo(int[42]);
 
 (Dave Tribby)
 
+209. The native code peephole optimizer might not correctly analyze whether short branch instructions can be used around an asm statement with one or more dcl directives.  This could cause "Relative address out of range" linker errors in some cases, or generate bad code without reporting any errors in others.
+
 -- Bugs from C 2.1.0 that have been fixed -----------------------------------
 
 1.  In some situations, fread() reread the first 1K or so of the file.