Chapter 25: add separate compilation and simplify SSA construction

Introduce Chapter 25 with separately compiled Simple modules, serialized IR,
cross-compilation-unit linking, and native system-library integration.  This
also completes a broad parser and type-system cleanup needed to make graph
construction independent of incomplete parse-time type information.

Separate compilation and linking

- Add compilation-unit Start/Stop nodes and track functions, classes, aliases,
  and global indices across compilation-unit boundaries.
- Serialize canonical types and ideal graph nodes into ELF objects, including
  dependency metadata, relocations, global/local bitset remapping, and dense
  memory-alias information.
- Load dependent objects on demand, recursively resolve source and object
  paths, relink calls and function pointers, and preserve external C symbols.
- Distinguish the post-optimization ownership hook from unknown callers so
  private call graphs can remain precise while public functions remain
  externally callable.
- Add command-line and build support for compiling modules and the reusable
  `sys` object library.

Parser, constructors, and SSA

- Replace inline constructor expansion with a hidden default `<init>` followed
  by an explicit user constructor declared as `new Type = { ... }`.
- Keep the default constructor private, pass private object memory through
  constructor calls, and require user constructors to initialize non-default
  fields before the object escapes.
- Track possibly-uninitialized fields in parser `Var` state and diagnose early
  reads without encoding parser-only constraints in Load and Store nodes.
- Make ordinary parser memory bulk and recover precise alias slices in the
  optimizer using `MemMerge`, `MemPhi`, and `BulkMemPhi` nodes.
- Remove parser-supplied type constraints from Loads and ordinary Phis, defer
  integer/float arithmetic selection, and keep call shape driven by syntax
  instead of provisional inferred types.
- Preserve chained field declarations as static parser information when flow
  types are not yet available, including postfix field updates through calls.

Types, functions, and escape analysis

- Add `TypeScalar` as the common lattice family for integer, float, memory
  pointer, and function-pointer values, with scalar TOP/BOT values for generic
  Loads, Stores, parameters, and invalid intermediate expressions.
- Represent unresolved struct definitions directly with the `TypeStruct`
  forward-reference flag while retaining the separate open-structure concept;
  close and canonicalize recursive structures without side maps.
- Add explicit `FunPtrNode` references so constant function pointers retain a
  graph edge to their Return, and keep referenced functions alive until Opto
  proves the pointer dead.
- Refine public-function and class-initializer escape handling, including
  public-only fallback escape sets and monotone compilation-unit summaries.
- Add guards, proof casts, read-only propagation, pointer-to-integer conversion
  for non-null FFI arguments, and consistent deep mutability checks at calls.

Optimization and code generation

- Make weak and unresolved graph inputs compute conservatively and monotonically
  throughout iterative peepholes and SCCP.
- Preserve independent memory slices when sharpening Stores, retain control on
  conditional Stores, and freeze Store widths from their target field types.
- Extend serialization for new node kinds, scalar types, Store modes, function
  pointers, and memory partitions, preserving serialize/deserialize bijection.
- Complete native selection and encoding support across x86-64, RISC-V, and
  ARM, including FFI pointer conversion and missing integer operations.
- Fix x86 immediate multiply REX encoding and assorted scheduling, register
  allocation, spilling, relocation, and constant-pool issues exposed by the
  larger linked graphs.

System library, tests, and documentation

- Compile and link the Simple `sys` library, including libc bindings, I/O,
  scanners, strings, vectors, array helpers, and executable entry points.
- Add Chapter 25 module, serialization, constructor, forward-reference,
  postfix-update, system, Hello World, and Bubble Sort coverage; update golden
  graphs and spill expectations for the new IR shape.
- Add module and type-system documentation, parser-simplification design notes,
  grammar updates, examples, diagrams, and graph visualization assets.

The resulting compiler passes the raw Chapter 1-24 suite and the Chapter 25
system and separate-compilation tests, including a freshly rebuilt `sys.o` and
the native Bubble Sort example.

1 files changed, 203 insertions, 0 deletions

diff --git a/chapter25/docs/lattice.gv b/chapter25/docs/lattice.gv
new file mode 100644
index 00000000..8661082d
--- /dev/null
+++ b/chapter25/docs/lattice.gv
@@ -0,0 +1,203 @@
+digraph Lattice {
+    compound = true;
+    // Define nodes
+    splines=false;
+    node [shape=circle, style=filled];
+    nodesep=0.2;
+    ranksep=0.2;
+
+    TOP [label=<<B>⊤</B >>, fillcolor=black, fontcolor=white];
+    BOT [label=<<B>⊥</B>>, fillcolor=black, fontcolor=white];
+
+    // ----------------------
+    // Control
+    XCTRL [label=<<B>⊤</B >:ctrl>, fillcolor=yellow, shape=oval];
+    CTRL  [label=<<B>⊥</B>:ctrl>, fillcolor=yellow, shape=oval];
+
+    TOP   -> XCTRL;
+    XCTRL -> CTRL;
+    CTRL  -> BOT;
+
+    // ----------------------
+    // Integers
+    INT_TOP [label=<<B>⊤</B >:int>, fillcolor=lightblue, shape=oval];
+    INT_BOT [label=<<B>⊥</B>:int>, fillcolor=lightblue, shape=oval];
+
+    INT_HI    [label="[min>max]" , fillcolor=lightblue, shape=oval];
+    INT_XBOOL [label="[1...0]", fillcolor=lightblue, shape=oval];
+    INT_CON   [label="constants", fillcolor=lightblue, shape=oval];
+    INT_CON0  [label="0", fillcolor=lightblue];
+    INT_CON1  [label="1", fillcolor=lightblue];
+    INT_BOOL  [label="[0...1]", fillcolor=lightblue,shape=oval];
+    INT_LO    [label="[min<max]" , fillcolor=lightblue, shape=oval];
+
+    TOP        -> INT_TOP;
+    INT_TOP    -> INT_HI;
+    INT_HI     -> INT_XBOOL;
+    INT_XBOOL  -> INT_CON0;
+    INT_XBOOL  -> INT_CON1;
+    INT_HI     -> INT_CON;
+    INT_CON0   -> INT_BOOL;
+    INT_CON1   -> INT_BOOL;
+    INT_BOOL   -> INT_LO;
+    INT_CON    -> INT_LO;
+    INT_LO     -> INT_BOT;
+    INT_BOT    -> BOT;
+
+    INT_CON0 -> INT_CON1 -> INT_CON [style=invis];
+
+    // ----------------------
+    // Floats
+    FLT_TOP [label=<<B>⊤</B >:flt>, fillcolor=aqua, shape=oval];
+    FLT_BOT [label=<<B>⊥</B>:flt>, fillcolor=aqua, shape=oval];
+
+    FLT_CON64  [label="64b consts\n[excludes\n32b consts]" , fillcolor=aqua, shape=oval];
+    FLT_CON32  [label="32b consts", fillcolor=aqua, shape=oval];
+    FLT_CONPI  [label="3.14159...", fillcolor=aqua, shape=oval];
+    FLT_X32    [label="~f32", fillcolor=aqua];
+    FLT_CON0   [label="0."  , fillcolor=aqua];
+    FLT_32     [label="f32" , fillcolor=aqua];
+
+    TOP       -> FLT_TOP;
+    FLT_TOP   -> FLT_CON64
+    FLT_TOP   -> FLT_CONPI
+    FLT_CON64 -> FLT_BOT
+    FLT_CONPI -> FLT_BOT
+    
+    FLT_TOP   -> FLT_X32;
+    FLT_X32   -> FLT_CON0;
+    FLT_X32   -> FLT_CON32;
+    FLT_CON0  -> FLT_32;
+    FLT_CON32 -> FLT_32;
+    FLT_32    -> FLT_BOT
+    
+    FLT_BOT   -> BOT;
+
+    FLT_CON0 -> FLT_CON32 -> FLT_CONPI -> FLT_CON64 [style=invis];
+
+
+    // ----------------------
+    // Pointers, just a boolean nil/not and a struct
+    PTR  [shape=none, fillcolor=none, label=<
+      <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+        <TR><TD BGCOLOR="green"><FONT color="white">*ptr</FONT></TD></TR>
+        <TR><TD BGCOLOR="lightgreen">struct</TD></TR>
+      </TABLE>
+    >];
+    PTR0  [shape=none, fillcolor=none, label=<
+      <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+        <TR><TD BGCOLOR="green"><FONT color="white">*ptr?</FONT></TD></TR>
+        <TR><TD BGCOLOR="lightgreen">struct</TD></TR>
+      </TABLE>
+    >];
+    
+    TOP  -> PTR;
+    PTR  -> PTR0;
+    PTR0 -> BOT;
+
+    // ----------------------
+    // Structs
+    STRUCT_TOP    [label=<<B>⊤</B >:struct>, fillcolor=lightgreen, shape=oval];
+    STRUCT_BOT    [label=<<B>⊥</B>:struct>, fillcolor=lightgreen, shape=oval];
+
+    STRUCT_S1  [shape=none, fillcolor=none, label=<
+      <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+        <TR><TD BGCOLOR="lightgreen">field</TD><TD BGCOLOR="lightblue:green" gradientangle="315">int/ptr</TD></TR>
+      </TABLE>
+    >];
+    STRUCT_S2  [shape=none, fillcolor=none, label=<
+      <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+        <TR><TD BGCOLOR="lightgreen">field</TD><TD BGCOLOR="lightblue:green" gradientangle="315">int/ptr</TD></TR>
+        <TR><TD BGCOLOR="lightgreen">field</TD><TD BGCOLOR="lightblue:green" gradientangle="315">int/ptr</TD></TR>
+      </TABLE>
+    >];
+    STRUCT_SN  [shape=none, fillcolor=none, label=<
+      <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+        <TR><TD BGCOLOR="lightgreen">field</TD><TD BGCOLOR="lightblue:green" gradientangle="315">int/ptr</TD></TR>
+        <TR><TD BGCOLOR="lightgreen">...  </TD><TD BGCOLOR="lightblue:green" gradientangle="315">int/ptr</TD></TR>
+        <TR><TD BGCOLOR="lightgreen">field</TD><TD BGCOLOR="lightblue:green" gradientangle="315">int/ptr</TD></TR>
+      </TABLE>
+    >];
+
+
+    TOP          -> STRUCT_TOP;
+    STRUCT_TOP   -> STRUCT_S1;
+    STRUCT_TOP   -> STRUCT_S2;
+    STRUCT_TOP   -> STRUCT_SN;
+    STRUCT_S1    -> STRUCT_BOT;
+    STRUCT_S2    -> STRUCT_BOT;
+    STRUCT_SN    -> STRUCT_BOT;
+    STRUCT_BOT   -> BOT;
+
+    STRUCT_S1 -> STRUCT_S2 -> STRUCT_SN [style=invis];
+
+    // ----------------------
+    // Memory
+    MEM_TOP       [label=<<B>⊤</B >:mem>, fillcolor=blue, fontcolor=white, shape=oval];
+    MEM_BOT       [label=<<B>⊥</B>:mem>, fillcolor=blue, fontcolor=white, shape=oval];
+    MEM_ALIAS1    [label="#1"     , fillcolor=blue, fontcolor=white];
+    MEM_ALIASDOTS [label="..."    , fillcolor=blue, fontcolor=white, shape=oval];
+    MEM_ALIASN    [label="#n"     , fillcolor=blue, fontcolor=white];
+
+    TOP          -> MEM_TOP;
+    MEM_TOP      -> MEM_ALIAS1;
+    MEM_TOP      -> MEM_ALIASDOTS;
+    MEM_TOP      -> MEM_ALIASN;
+    MEM_ALIAS1   -> MEM_BOT;
+    MEM_ALIASDOTS -> MEM_BOT;
+    MEM_ALIASN    -> MEM_BOT;
+    MEM_BOT       -> BOT;
+
+    MEM_ALIAS1 -> MEM_ALIASDOTS -> MEM_ALIASN [style=invis];
+
+    // ----------------------
+    // Tuples
+
+    TUPLE_TOP [label=<<B>⊤</B >:tuple>, fillcolor=pink, shape=oval];
+    TUPLE_BOT [label=<<B>⊥</B>:tuple>, fillcolor=pink, shape=oval];
+
+    TUPLE1 [shape=none, fillcolor=none, label=<
+      <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+        <TH><TD BGCOLOR="pink">Tuple</TD></TH>
+        <TR><TD BGCOLOR="black" ><FONT color="white">type</FONT></TD></TR>
+      </TABLE>
+    >];
+    TUPLE2 [shape=none, fillcolor=none, label=<
+      <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+        <TH><TD BGCOLOR="pink">Tuple</TD></TH>
+        <TR><TD BGCOLOR="black" ><FONT color="white">type</FONT></TD></TR>
+        <TR><TD BGCOLOR="black" ><FONT color="white">type</FONT></TD></TR>
+      </TABLE>
+    >];
+    TUPLEN [shape=none, fillcolor=none, label=<
+      <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+        <TH><TD BGCOLOR="pink">Tuple</TD></TH>
+        <TR><TD BGCOLOR="black" ><FONT color="white">type</FONT></TD></TR>
+        <TR><TD BGCOLOR="black" ><FONT color="white">...</FONT></TD></TR>
+        <TR><TD BGCOLOR="black" ><FONT color="white">type</FONT></TD></TR>
+      </TABLE>
+    >];
+
+
+    TOP -> TUPLE_TOP;
+    TUPLE_TOP -> TUPLE1;
+    TUPLE_TOP -> TUPLE2;
+    TUPLE_TOP -> TUPLEN;
+    TUPLE1 -> TUPLE_BOT;
+    TUPLE2 -> TUPLE_BOT;
+    TUPLEN -> TUPLE_BOT;
+    TUPLE_BOT -> BOT;
+
+    // ----------------------
+    // Additional customization
+    {rank=same; TOP;}
+    {rank=same; INT_TOP; FLT_TOP; XCTRL; PTR; STRUCT_TOP; MEM_TOP; TUPLE_TOP}
+    {rank=same; INT_CON; INT_CON0; INT_CON1;
+                FLT_CON32; FLT_CON64;  FLT_CON0; FLT_CONPI;
+                STRUCT_S1; STRUCT_S2; STRUCT_SN;
+                MEM_ALIAS1;  MEM_ALIASDOTS; MEM_ALIASN;
+                TUPLE1; TUPLE2; TUPLEN;
+    }
+    {rank=same; INT_BOT; FLT_BOT; CTRL; PTR0; STRUCT_BOT; MEM_BOT; TUPLE_BOT}
+    {rank=same; BOT;}
+}