[Oberon] On a code generated for Math.Mod.txt

[Peter De Wachter]

The disassembly of ORTool can be misleading, I suspect the module
predates the current revision of the RISC architecture. Try applying
the attached patch, it should make it a bit clearer. With that and the
RISC Architecture document you should be able to figure it out.

On Wed, Jul 13, 2016 at 9:18 PM, Srinivas Nayak
<sinu.nayak2001 at gmail.com> wrote:
> In math.Mod.txt we see
>
> q0 =  9.9999999E-1;
> IF ODD(n) THEN f := (((((q6*yy + q5)*yy + q4)*yy + q3)*yy + q2)*yy + q1)*yy
> + q0
>
> ELSE
>
> For the last addition of q0, I see the code generated is:
>
> 61003F7F  MOV'  R1  R0  16255
>
> 4116FFFE  IOR  R1  R1     -2
>
> How it is different from
>
> 61003F80  MOV'  R1  R0  16256
>
>
>
>
> With thanks and best regards,
>
> Yours sincerely,
> Srinivas Nayak
>
> Home: http://www.mathmeth.com/sn/
> Blog: http://srinivas-nayak.blogspot.in/
> --
> Oberon at lists.inf.ethz.ch mailing list for ETH Oberon and related systems
> https://lists.inf.ethz.ch/mailman/listinfo/oberon
-------------- next part --------------
--- ORTool.Old.Mod	2016-07-13 23:31:59.462406325 +0200
+++ ORTool.New.Mod	2016-07-13 23:31:59.462406325 +0200
@@ -108,13 +108,14 @@
   END WriteReg;
 
   PROCEDURE opcode(w: LONGINT);
-    VAR k, op, u, a, b, c: LONGINT;
+    VAR k, op, u, v, a, b, c: LONGINT;
   BEGIN
       k := w DIV 40000000H MOD 4;
       a := w DIV 1000000H MOD 10H;
       b := w DIV 100000H MOD 10H;
       op := w DIV 10000H MOD 10H;
       u := w DIV 20000000H MOD 2;
+      v := w DIV 10000000H MOD 2;
       IF k = 0 THEN
         Texts.WriteString(W, mnemo0[op]);
         IF u = 1 THEN Texts.Write(W, "'") END ;
@@ -122,8 +123,9 @@
       ELSIF k = 1 THEN
         Texts.WriteString(W, mnemo0[op]);
         IF u = 1 THEN Texts.Write(W, "'") END ;
-        WriteReg(a); WriteReg(b); w := w MOD 10000H;
-        IF w >= 8000H THEN w := w - 10000H END ;
+        WriteReg(a); IF op # 0 THEN WriteReg(b) END ;
+        w := w MOD 10000H;
+        IF v = 1 THEN w := w - 10000H END ;
         Texts.WriteInt(W, w, 7)
       ELSIF k = 2 THEN  (*LDR/STR*)
         IF u = 1 THEN Texts.WriteString(W, "STR ") ELSE Texts.WriteString(W, "LDR") END ;