From 3a3d469154846b648b09c708bfe3e8c16a203654 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Mon, 13 Jan 2025 15:09:59 -0800
Subject: Some dead inf call bug fixes

More comments about meeting nil above the center line falls - but does not (can not) dual.
This implies have TFPs with *no* allowed functions that are below centerline; if allowed null then its basically an alternate null.  If not allowed null and not allowed any functions, its basically a high value (not executable).  IfNode folds.

Do not remove a dead infinite loop - it needs to remain as a CFG sink.
---
 chapter18/src/main/java/com/seaofnodes/simple/Parser.java  |  3 ++-
 .../main/java/com/seaofnodes/simple/node/CallEndNode.java  |  9 +++++----
 .../src/main/java/com/seaofnodes/simple/node/IfNode.java   |  2 +-
 .../src/main/java/com/seaofnodes/simple/node/LoopNode.java | 14 +++++++++++++-
 .../main/java/com/seaofnodes/simple/node/RegionNode.java   |  2 +-
 .../main/java/com/seaofnodes/simple/node/ReturnNode.java   |  6 ++++--
 .../main/java/com/seaofnodes/simple/type/TypeFunPtr.java   |  9 +++++----
 .../main/java/com/seaofnodes/simple/type/TypeMemPtr.java   |  7 ++-----
 8 files changed, 33 insertions(+), 19 deletions(-)

(limited to 'chapter18/src/main/java')

diff --git a/chapter18/src/main/java/com/seaofnodes/simple/Parser.java b/chapter18/src/main/java/com/seaofnodes/simple/Parser.java
index 649145fd..8f0cf493 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/Parser.java
@@ -708,7 +708,8 @@ public class Parser {
             if( inferType ) {
                 if( expr._type==Type.NIL )
                     throw error("a not-null/non-zero expression");
-                t = expr._type.glb();
+                t = expr._type;
+                if( !xfinal ) t = t.glb();  // Widen if not final
             }
             if( t instanceof TypeFunPtr && expr._type instanceof TypeFunPtr tfp && tfp.isConstant() )
                 tfp.setName(name);
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/CallEndNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/CallEndNode.java
index c9ea2f1f..48edc0eb 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/CallEndNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/CallEndNode.java
@@ -26,8 +26,7 @@ public class CallEndNode extends CFGNode implements MultiNode {
     @Override
     StringBuilder _print1(StringBuilder sb, BitSet visited) {
         sb.append("cend( ");
-        if( call()==null ) sb.append("---, ");
-        else sb.append("Call, ");
+        sb.append( in(0) instanceof CallNode ? "Call, " : "----, ");
         for( int i=1; i<nIns()-1; i++ )
             in(i)._print0(sb,visited).append(",");
         sb.setLength(sb.length()-1);
@@ -36,8 +35,10 @@ public class CallEndNode extends CFGNode implements MultiNode {
 
     @Override
     public Type compute() {
-        Type ret = call().fptr()._type instanceof TypeFunPtr tfp ? tfp.ret() : Type.BOTTOM;
-        return TypeTuple.make(call()._type,TypeMem.BOT,ret);
+        if( !(in(0) instanceof CallNode call) )
+            return TypeTuple.RET.dual();
+        Type ret = call.fptr().addDep(this)._type instanceof TypeFunPtr tfp ? tfp.ret() : Type.BOTTOM;
+        return TypeTuple.make(call._type,TypeMem.BOT,ret);
     }
 
     @Override
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/IfNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/IfNode.java
index 1e6b2878..c49ee662 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/IfNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/IfNode.java
@@ -43,7 +43,7 @@ public class IfNode extends CFGNode implements MultiNode {
         // If constant is 0 then false branch is reachable
         // Else true branch is reachable
         if( t.isConstant() )
-            return (t==Type.NIL || t==TypeInteger.ZERO) ? TypeTuple.IF_FALSE : TypeTuple.IF_TRUE;
+            return (t==Type.NIL || t==TypeInteger.ZERO || (t instanceof TypeFunPtr tfp && tfp._fidxs==0) ) ? TypeTuple.IF_FALSE : TypeTuple.IF_TRUE;
         // If adding a zero makes a difference, the predicate must not have a zero/null
         if( !t.makeZero().isa(t) )
             return TypeTuple.IF_TRUE;
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/LoopNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/LoopNode.java
index b54403b7..a31c8ac8 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/LoopNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/LoopNode.java
@@ -25,7 +25,19 @@ public class LoopNode extends RegionNode {
 
     @Override
     public Node idealize() {
-        return inProgress() ? null : super.idealize();
+        if( inProgress() ) return null;
+        // Dead infinite loops with NO control flow out stick around - as a
+        // dead infinite loop, to signal that control stops and spins here.
+        if( nIns()==2 && !hasPhi() && !hasCFG() )
+            return null;
+        return super.idealize();
+    }
+
+    private boolean hasCFG() {
+        for( Node phi : _outputs )
+            if( phi instanceof CFGNode )
+                return true;
+        return false;
     }
 
     // Bypass Region idom, same as the default idom() using use in(1) instead of in(0)
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/RegionNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/RegionNode.java
index 5045b43b..d8e24964 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/RegionNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/RegionNode.java
@@ -86,7 +86,7 @@ public class RegionNode extends CFGNode {
         return 0;               // All inputs alive
     }
 
-    private boolean hasPhi() {
+    boolean hasPhi() {
         for( Node phi : _outputs )
             if( phi instanceof PhiNode )
                 return true;
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
index f42adcf6..2fe722c6 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
@@ -45,12 +45,14 @@ public class ReturnNode extends CFGNode {
 
     @Override
     public Type compute() {
-        if( inProgress() ) return TypeTuple.RET; // In progress
+        if( inProgress () ) return TypeTuple.RET; // In progress
+        if( _fun.isDead() ) return TypeTuple.RET.dual(); // Dead another way
         return TypeTuple.make(ctrl()._type,mem()._type,expr()._type);
     }
 
     @Override public Node idealize() {
-        if( inProgress() ) return null;
+        if( inProgress () ) return null;
+        if( _fun.isDead() ) return null;
 
         // Upgrade signature based on return type
         Type ret = expr()._type;
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java
index 5799fea9..cf92d3d7 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java
@@ -24,7 +24,7 @@ public class TypeFunPtr extends TypeNil {
     // Cheesy easy implementation for a small set; 1 bit per unique function
     // within the TypeTuple.  Can be upgraded to a BitSet for larger classes of
     // functions.  Negative means "these 63 concrete bits plus infinite unknown more"
-    private final long _fidxs; // 63 unique functions per signature
+    public final long _fidxs; // 63 unique functions per signature
     public String _name; // Optional debug function name; only for named single function
 
     private TypeFunPtr(byte nil, TypeTuple sig, Type ret, long fidxs) {
@@ -69,12 +69,13 @@ public class TypeFunPtr extends TypeNil {
     @Override
     public TypeFunPtr dual() { return TypeFunPtr.make(dual0(), _sig.dual(), _ret.dual(), ~_fidxs); }
 
-    // RHS is NIL
+    // RHS is NIL; do not deep-dual when crossing the centerline
     @Override public Type meet0() { return _nil==3 ? this : make((byte)3,_sig,_ret,_fidxs); }
 
-    @Override public TypeFunPtr glb() { return make(_nil,_sig,_ret,_fidxs); }
+    @Override public TypeFunPtr glb() { return make((byte)3,_sig,_ret,-1L); }
 
-    @Override public boolean isConstant() { return _nil==2 && Long.bitCount(_fidxs)==1; }
+    @Override public boolean isHigh    () { return _nil <= 1 || (_nil==2 && _fidxs==0); }
+    @Override public boolean isConstant() { return (_nil==2 && Long.bitCount(_fidxs)==1) || (_nil==3 && _fidxs==0); }
 
     @Override public int log_size() { return 2; } // (1<<2)==4-byte pointers
 
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java
index c8a5c1f4..d7a8b17d 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java
@@ -58,11 +58,8 @@ public class TypeMemPtr extends TypeNil {
     @Override
     public TypeMemPtr dual() { return TypeMemPtr.make( dual0(), _obj.dual()); }
 
-    // RHS is NIL
-    @Override Type meet0() {
-        // NOT DOING DUAL
-        return _nil==3 ? this : make((byte)3,_obj);
-    }
+    // RHS is NIL; do not deep-dual when crossing the centerline
+    @Override Type meet0() { return _nil==3 ? this : make((byte)3,_obj); }
 
 
     // True if this "isa" t up to named structures
-- 
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