Cleanup main handling

Author: cliffclick

chapter25/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java

@@ -135,14 +135,14 @@ public CodeGen driver( Phase phase, String cpu, String callingConv ) {
             return driver(phase,cpu,callingConv,false,false,0);
         if( _srcName == null )
             throw new RuntimeException("No source filename provided, so do not know how to name the obj file");
-        boolean main = !_srcName.contains(".");
-        return driver( phase, cpu, callingConv, false, main, 0 );
+        boolean emitEntrySymbol = !_srcName.contains(".");
+        return driver( phase, cpu, callingConv, false, emitEntrySymbol, 0 );
     }
     // Write an object file for a specific cpu/os pair
 
-    public CodeGen driver( String cpu, String callingConv, boolean inMemory, boolean main ) { return driver(Phase.Export,cpu,callingConv,inMemory,main,0); }
+    public CodeGen driver( String cpu, String callingConv, boolean inMemory, boolean emitEntrySymbol ) { return driver(Phase.Export,cpu,callingConv,inMemory,emitEntrySymbol,0); }
     // Generic driver
-    public CodeGen driver( Phase phase, String cpu, String callingConv, boolean inMemory, boolean main, int dump ) {
+    public CodeGen driver( Phase phase, String cpu, String callingConv, boolean inMemory, boolean emitEntrySymbol, int dump ) {
         int p1 = phase.ordinal(), p2 = _phase==null ? -1 : _phase.ordinal();
         if( p2 < p1 && p2 <  Phase.Parse     .ordinal() ) { parse();     p2 = dump(dump); }
         if( p2 < p1 && p2 <  Phase.Iter      .ordinal() ) { iter();      p2 = dump(dump); }
@@ -156,10 +156,14 @@ public CodeGen driver( Phase phase, String cpu, String callingConv, boolean inMe
         if( p2 < p1 && p2 <  Phase.LocalSched.ordinal() ) { localSched();p2 = dump(dump); }
         if( p2 < p1 && p2 <  Phase.RegAlloc  .ordinal() ) { regAlloc();  p2 = dump(dump); }
         if( p2 < p1 && p2 <  Phase.Encoding  .ordinal() ) { encode();    p2 = dump(dump); }
-        if( p2 < p1 && p2 <  Phase.Export    .ordinal() ) { exportELF(inMemory,main); p2 = dump(dump); }
+        if( p2 < p1 && p2 <  Phase.Export    .ordinal() ) { exportELF(inMemory,emitEntrySymbol); p2 = dump(dump); }
         return this;
     }
 
+    public String entryClinitName() {
+        return Parser.addClzPrefix(_srcName==null ? "Test" : _srcName)+".<clinit>";
+    }
+
     // Verbose printing during compilation
     private int dump(int dump) {
         int p2 = _phase.ordinal();
@@ -672,15 +676,15 @@ public CodeGen encode() {
     // ---------------------------
     // Exporting to external formats
     ElfWriter _elf;
-    public CodeGen exportELF( boolean inMemory, boolean main ) {
+    public CodeGen exportELF( boolean inMemory, boolean emitEntrySymbol ) {
         assert _phase == Phase.Encoding;
         _phase = Phase.Export;
         long t0 = System.currentTimeMillis();
         if( _encoding!=null ) {
             if( inMemory )
                 new LinkMem(this).link(_encoding); // In memory patching
             else
-                _elf = new ElfWriter(this).export(main);
+                _elf = new ElfWriter(this).export(emitEntrySymbol);
         }
         _times[Phase.Export.ordinal()] = System.currentTimeMillis() - t0;
         return this;

chapter25/src/main/java/com/seaofnodes/simple/codegen/ElfWriter.java

@@ -1,6 +1,5 @@
 package com.seaofnodes.simple.codegen;
 
-import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.node.*;
 import com.seaofnodes.simple.type.TypeStruct;
 import com.seaofnodes.simple.util.Ary;
@@ -196,14 +195,15 @@ void encodeFunctions(StopNode stop, Encoding enc, int text_idx) {
             }
         }
 
-        void symbolMain(int text_idx, Encoding enc) {
-            String mainName = Parser.addClzPrefix(_code._srcName==null ? "Test" : _code._srcName)+".<clinit>";
+        void symbolEntryClinit(int text_idx, Encoding enc) {
+            String entryName = _code.entryClinitName();
             for( FunNode fun : _code._linker )
-                if( fun != null && mainName.equals(fun._name) ) {
+                if( fun != null && entryName.equals(fun._name) ) {
+                    assert enc.opStart(fun) == 0;
                     symbol("main",text_idx, SYM_BIND_GLOBAL, SYM_TYPE_FUNC, enc.opStart(fun), 0);
                     return;
                 }
-            throw new IllegalStateException("Missing main function "+mainName);
+            throw new IllegalStateException("Missing entry <clinit> "+entryName);
         }
 
         static void write2( BAOS bits, int op ) {
@@ -256,7 +256,7 @@ public class SimpleSection extends DataSection {
 
     // ------------------------------------------------------------------------
 
-    public ElfWriter export(boolean main) {
+    public ElfWriter export(boolean emitEntrySymbol) {
         // Sections are created in the order they are emitted.
         _sections = new Ary<>(Section.class);
 
@@ -282,9 +282,10 @@ public ElfWriter export(boolean main) {
 
         // populate function symbols
         symbols.encodeFunctions(_code._stop, _code._encoding, text._index);
-        // The "main" symbol, starting code is always location 0
-        if( main )
-            symbols.symbolMain(text._index,enc);
+        // Export the source compilation unit <clinit> as the C runtime "main".
+        // Encoding keeps this function at text offset zero.
+        if( emitEntrySymbol )
+            symbols.symbolEntryClinit(text._index,enc);
 
         // create external .text relocations
         ReloSection relocations = new ReloSection(text._index);

chapter25/src/main/java/com/seaofnodes/simple/codegen/Encoding.java

@@ -217,13 +217,13 @@ private void basicBlockLayout( ) {
 
         // Do them all except the <clinit>s
         Ary<FunNode> clinits = new Ary<>(FunNode.class);
-        FunNode main = null;
-        String mainName = Parser.addClzPrefix(_code._srcName==null ? "Test" : _code._srcName)+".<clinit>";
+        FunNode entry = null;
+        String entryName = _code.entryClinitName();
         for( FunNode fun : _code._linker ) {
             if( fun != null && !fun.isDead() ) {
                 if( fun.isClz() ) {
-                    if( fun._name.equals(mainName) )
-                        main = fun;
+                    if( fun._name.equals(entryName) )
+                        entry = fun;
                     else
                         clinits.add(fun);
                 } else {
@@ -240,9 +240,9 @@ private void basicBlockLayout( ) {
             _rpo_cfg(clinit,visit,rpos);
             assert _cfg.at(x) instanceof ReturnNode;
         }
-        if( main != null ) {
+        if( entry != null ) {
             int x = _cfg._len;
-            _rpo_cfg(main,visit,rpos);
+            _rpo_cfg(entry,visit,rpos);
             assert _cfg.at(x) instanceof ReturnNode;
         }
 

chapter25/src/main/java/com/seaofnodes/simple/node/FunNode.java

@@ -126,9 +126,9 @@ public Type compute() {
             return Type.CONTROL;
         Type t = Type.XCONTROL;
         for (int i = 1; i < nIns(); i++) {
-            // Since no unknown callers, we are not main and the Start input
-            // will be a Tuple with XControl, so ignore it.  Need to be called
-            // from someplace other than Start
+            // Since there are no unknown callers, the Start input is only a
+            // fake hook and will be a Tuple with XControl, so ignore it.  Need
+            // to be called from someplace other than Start.
             if( !(in(i) instanceof StartNode) )
                 t = t.meet(in(i)._type);
         }
@@ -138,7 +138,7 @@ public Type compute() {
     @Override
     public Node idealize() {
 
-        // Some linked path dies, except main never kills Start
+        // Some linked path dies, except unknown caller hooks never kill Start.
         Node progress = deadPath(unknownCallers());
         if( progress!=null ) {
             if( nIns()==2 && in(1) instanceof CallNode call )

chapter25/src/main/java/com/seaofnodes/simple/node/StartNode.java

@@ -9,18 +9,18 @@
 import java.util.HashSet;
 
 /**
- * The Start node represents the external world calling, be it calling main or
- * just some linked caller calling.
+ * The Start node represents the external world calling, be it calling the
+ * entry <clinit> or just some linked caller calling.
  * <p>
  * Start initially has 1 input (arg) from outside and the initial control.
  * In ch10 we also add mem aliases as structs get defined; each field in struct
  * adds a distinct alias to Start's tuple.
  * <p>
  * By ch25, Start is the external world (or linker) calling with everything
- * that has escaped.  Start is NOT the FunNode called *main* (which can assume
- * no memory nor fidxs exist nor escaped).  Start gets escaped things from
- * Stop; together these close the Grand Cycle between the code we know and the
- * code we don't.
+ * that has escaped.  Start is NOT the entry <clinit> itself, which can assume
+ * no memory nor fidxs exist nor escaped.  Start gets escaped things from Stop;
+ * together these close the Grand Cycle between the code we know and the code
+ * we don't.
  */
 public class StartNode extends LoopNode implements MultiNode {