From 19683706ccf2f59dc984de1e012fbee66cf06da2 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Wed, 12 Oct 2022 22:03:37 -0500
Subject: [PATCH] Do not optimize code from asm statements.

Previously, the assembly-level optimizations applied to code in asm statements. In many cases, this was fine (and could even do useful optimizations), but occasionally the optimizations could be invalid. This was especially the case if the assembly involved tricky things like self-modifying code.

To avoid these problems, this patch makes the assembly optimizers ignore code from asm statements, so it is always emitted as-is, without any changes.

This fixes #34.
---
 CGI.pas    |  2 ++
 Gen.pas    | 14 +++++++++-----
 Native.asm |  6 ++++--
 Native.pas |  5 +++--
 cc.notes   |  4 ++++
 5 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/CGI.pas b/CGI.pas
index 7ed8546..674227c 100644
--- a/CGI.pas
+++ b/CGI.pas
@@ -207,6 +207,8 @@ const
    d_cns                  =    263;
 
    max_opcode             =    263;
+   
+   asmFlag                =  $8000;     {or'd with opcode to indicate asm code}
 
                                         {Code Generation}
                                         {---------------}
diff --git a/Gen.pas b/Gen.pas
index 50710bd..ccabb39 100644
--- a/Gen.pas
+++ b/Gen.pas
@@ -6725,30 +6725,34 @@ procedure GenTree {op: icptr};
       mode: addressingmode;		{work var for addressing mode}
       pval: longint;			{temp pointer}
       val: longint;			{constant operand}
+      opcode: integer;			{opcode}
 
    begin {GenNat}
    val := op^.opnd;
    flags := op^.q;
    pval := op^.llab;
    mode := addressingMode(op^.r);
+   opcode := op^.s;
+   if opcode < 256 then
+      opcode := opcode | asmFlag;
    if op^.slab <> 0 then
       val := val+LabelToDisp(op^.slab);
    if mode in [relative,longrelative] then
-      GenNative(op^.s, mode, op^.llab, op^.lab, op^.q)
+      GenNative(opcode, mode, op^.llab, op^.lab, op^.q)
    else if (mode = longabsolute) and (op^.llab <> 0) then
-      GenNative(op^.s, mode, long(val).lsw, pointer(pval),
+      GenNative(opcode, mode, long(val).lsw, pointer(pval),
          flags | localLab)
    else if (mode = longabsolute) and (op^.llab = 0)
       and (op^.lab = nil) then
-      GenNative(op^.s, mode, 0, pointer(val), flags | constantOpnd)
+      GenNative(opcode, mode, 0, pointer(val), flags | constantOpnd)
    else begin
       if (mode = absolute) and (op^.llab = 0) then
          flags := flags | constantOpnd;
       if op^.llab <> 0 then
-         GenNative(op^.s, mode, long(val).lsw, pointer(pval),
+         GenNative(opcode, mode, long(val).lsw, pointer(pval),
             flags | localLab)
       else
-         GenNative(op^.s, mode, long(val).lsw, op^.lab, flags);
+         GenNative(opcode, mode, long(val).lsw, op^.lab, flags);
       end; {else}
    end; {GenNat}
 
diff --git a/Native.asm b/Native.asm
index afe45cd..32f99cf 100644
--- a/Native.asm
+++ b/Native.asm
@@ -87,7 +87,8 @@ lb1      lda   nPeep+peep_opcode,X        if npeep[i].opcode = d_lab then
          inc   fn
          bra   lab1                           goto 1;
 lb2      anop                                 end;
-         lda   nPeep+peep_opcode,X        len := len+size[npeep[i].mode];
+         lda   nPeep+peep_opcode,X        len := len+size[npeep[i].opcode & ~asmFlag];
+         and   #$7FFF
          tay
          lda   size,Y
          and   #$00FF
@@ -123,7 +124,8 @@ lb4      lda   i                        while i < nnextspot do begin
          inc   fn
          bra   lab1                           goto 1;
 lb5      anop                                 end;
-         lda   nPeep+peep_opcode,X        len := len+size[npeep[i].mode];
+         lda   nPeep+peep_opcode,X        len := len+size[npeep[i].opcode & ~asmFlag];
+         and   #$7FFF
          tay
          lda   size,Y
          and   #$00FF
diff --git a/Native.pas b/Native.pas
index 68e5de1..82c0d6a 100644
--- a/Native.pas
+++ b/Native.pas
@@ -494,6 +494,7 @@ case mode of
             if not longA then
                if operand = 255 then
                   goto 1;
+         opcode := opcode & ~asmFlag;
          CnOut(opcode);
          if opcode = m_pea then
             GenImmediate2
@@ -525,7 +526,7 @@ case mode of
 
    longabs: begin
       CnOut(opcode);
-      isJSL := opcode = m_jsl;          {allow for dynamic segs}
+      isJSL := (opcode & ~asmFlag) = m_jsl;     {allow for dynamic segs}
       if name = nil then
          if odd(flags div toolcall) then begin
             CnOut2(0);
@@ -721,7 +722,7 @@ case mode of
       end;
 
    genAddress: begin
-      if opcode < 256 then
+      if opcode < 256 then              {includes opcodes with asmFlag}
          CnOut(opcode);
       if (flags & stringReference) <> 0 then begin
          Purge;
diff --git a/cc.notes b/cc.notes
index eded887..a079122 100644
--- a/cc.notes
+++ b/cc.notes
@@ -1903,6 +1903,10 @@ int foo(int[42]);
 
 207. If a struct or union type with a tag T has been declared within an outer scope, a declaration "struct T;" or "union T;" within an inner scope should declare a separate type, distinct from the one in the outer scope.
 
+208. The native code peephole optimizer and register optimizer could alter the assembly code in asm statements, occasionally causing it not be behave as intended.  Now, code from asm statements will not be altered by the optimizers.
+
+(Dave Tribby)
+
 -- Bugs from C 2.1.0 that have been fixed -----------------------------------
 
 1.  In some situations, fread() reread the first 1K or so of the file.