From a5fb3fb98c67ff0d2803ba7b6c0cd9933e7d7001 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Tue, 1 Oct 2024 16:37:14 -0700
Subject: Sharpen null checks

Look for chances to sharpen checks of all kinds, especially null checks.
Not terribly cheap check, probably needs a O(n^2) check
Fix a bunch gold test result spelling.
---
 .../com/seaofnodes/simple/node/RegionNode.java     | 56 ++++++++++++++++++++++
 .../main/java/com/seaofnodes/simple/type/Type.java |  1 +
 .../com/seaofnodes/simple/type/TypeInteger.java    |  8 +++-
 .../com/seaofnodes/simple/type/TypeMemPtr.java     |  1 +
 4 files changed, 65 insertions(+), 1 deletion(-)

(limited to 'chapter15/src/main/java/com/seaofnodes')

diff --git a/chapter15/src/main/java/com/seaofnodes/simple/node/RegionNode.java b/chapter15/src/main/java/com/seaofnodes/simple/node/RegionNode.java
index d5105614..0c7cd1e4 100644
--- a/chapter15/src/main/java/com/seaofnodes/simple/node/RegionNode.java
+++ b/chapter15/src/main/java/com/seaofnodes/simple/node/RegionNode.java
@@ -72,9 +72,65 @@ public class RegionNode extends CFGNode {
             p1.in(0) instanceof IfNode iff )
             return iff.ctrl();
 
+
+
+        // Look for direct uses of a guarded expression, and replace with the guard result.
+        if( !(idom() instanceof StartNode) && // Dead or dying
+            !(this instanceof LoopNode) ) {
+            VISIT.clear();
+            boolean progress = false;
+            outer:
+            for( int i=1; i<nIns(); i++ ) {
+                CFGNode idom = cfg(i);
+                while( !(idom instanceof CProjNode cproj) ) {
+                    idom = idom.idom();
+                    if( idom==null || idom.idepth() < idom().idepth() )
+                        continue outer;
+                }
+                if( cproj.cfg0() instanceof IfNode iff && cproj.compute()==Type.CONTROL ) {
+                    VISIT.set(iff.pred()._nid);
+                    for( Node out : _outputs )
+                        if( out instanceof PhiNode phi )
+                            progress |= walk(iff,cproj,phi.in(i));
+                }
+            }
+            if( progress )
+                return this;
+        }
+
         return null;
     }
 
+    // A walk that can be cutoff early
+    private static final BitSet VISIT = new BitSet();
+    private static boolean walk( IfNode iff, CProjNode cproj, Node n ) {
+        if( VISIT.get(n._nid) ) return false;
+        VISIT.set(n._nid);
+        if( n instanceof CFGNode ) return false;
+        if( n.in(0)!=null && n.cfg0().idepth() < iff.idepth() )
+            return false;
+        boolean progress = false;
+        Node pred = iff.pred();
+        for( int i=1; i<n.nIns(); i++ ) {
+            // Using a tested value
+            if( n.in(i) == pred && !(n instanceof CastNode) ) {
+                // Checking pred for T/F
+                Type t = pred._type;
+                Type tcast = cproj._idx==0 ? t.nonZero() : t.makeInit();
+                if( t!=tcast ) { // Progress to cast
+                    Node cast = new CastNode( tcast, cproj, pred ).peephole();
+                    n.setDef( i, cast );
+                    IterPeeps.add(n);
+                    progress = true;
+                }
+            }
+            if( n.in(i)!=null )
+                progress |= walk(iff,cproj,n.in(i));
+        }
+        return progress;
+    }
+
+
     private int findDeadInput() {
         for( int i=1; i<nIns(); i++ )
             if( in(i)._type==Type.XCONTROL )
diff --git a/chapter15/src/main/java/com/seaofnodes/simple/type/Type.java b/chapter15/src/main/java/com/seaofnodes/simple/type/Type.java
index 983fcf98..989eff9e 100644
--- a/chapter15/src/main/java/com/seaofnodes/simple/type/Type.java
+++ b/chapter15/src/main/java/com/seaofnodes/simple/type/Type.java
@@ -82,6 +82,7 @@ public class Type {
     public StringBuilder typeName( StringBuilder sb) { return print(sb); }
 
     public Type makeInit() { return null; }
+    public Type nonZero() { return glb(); }
 
     // ----------------------------------------------------------
 
diff --git a/chapter15/src/main/java/com/seaofnodes/simple/type/TypeInteger.java b/chapter15/src/main/java/com/seaofnodes/simple/type/TypeInteger.java
index fca3362e..042b4ba8 100644
--- a/chapter15/src/main/java/com/seaofnodes/simple/type/TypeInteger.java
+++ b/chapter15/src/main/java/com/seaofnodes/simple/type/TypeInteger.java
@@ -113,8 +113,14 @@ public class TypeInteger extends Type {
     }
 
     @Override public TypeInteger dual() { return make(_max,_min); }
-    @Override public Type glb() { return BOT; }
+    @Override public TypeInteger glb() { return BOT; }
     @Override public TypeInteger makeInit() { return ZERO; }
+    @Override public TypeInteger nonZero() {
+        if( isHigh() ) return this;
+        if( _min==0 ) return make(1,_max); // specifically good on BOOL
+        if( _max==0 ) return make(_min,-1);
+        return this;
+    }
     @Override int hash() { return (int)((_min ^ (_min>>32)) *(_max ^ (_max>>32))); }
     @Override
     public boolean eq( Type t ) {
diff --git a/chapter15/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java b/chapter15/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java
index 7743c80d..8b484235 100644
--- a/chapter15/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java
+++ b/chapter15/src/main/java/com/seaofnodes/simple/type/TypeMemPtr.java
@@ -58,6 +58,7 @@ public class TypeMemPtr extends Type {
     @Override
     public TypeMemPtr glb() { return make(_obj.glb(),true); }
     @Override public TypeMemPtr makeInit() { return NULLPTR; }
+    @Override public Type nonZero() { return VOIDPTR; }
 
     @Override public boolean isHigh() { return this==TOP; }
 
-- 
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