Make RegMaskRW public and add mutating or; Fix coelesce bug (#186)

* Make RegMaskRW public and add union to it.

* Rename union to or

* Split popular non-constant

* Fix coelesce bug

---------

Co-authored-by: Cliff Click <cliffc@acm.org>

6 files changed, 39 insertions, 28 deletions

diff --git a/chapter21/src/main/java/com/seaofnodes/simple/codegen/Coalesce.java b/chapter21/src/main/java/com/seaofnodes/simple/codegen/Coalesce.java
index 89dde46f..255e4e5e 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/codegen/Coalesce.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/codegen/Coalesce.java
@@ -37,7 +37,7 @@ abstract public class Coalesce {
                 if( v1 != v2 ) {
                     LRG ov1 = v1, ov2 = v2;
                     // Get the smaller neighbor count in v1
-                    if( (v1._adj==null ? 0 : v1._adj._len) > (v2._adj==null ? 0 : v2._adj._len) )
+                    if( v1.nadj() > v2.nadj() )
                         { v1 = v2; v2 = alloc.lrg(n); }
                     int v2len = v2._adj==null ? 0 : v2._adj._len;
                     // See that they do not conflict (coalescing would make a self-conflict)
@@ -58,9 +58,9 @@ abstract public class Coalesce {
                     // Most constrained mask
                     RegMask mask = v1._mask==v2._mask ? v1._mask : v1._mask.copy().and(v2._mask);
                     // Check for capacity
-                    if( v2._adj!=null && v2._adj._len >= mask.size() ) {
+                    if( v2.nadj() >= mask.size() ) {
                         // Fails capacity, will not be trivial colorable
-                        v2._adj.setLen(v2len);
+                        if( v2._adj!=null ) v2._adj.setLen(v2len);
                         continue;
                     }
 
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/codegen/LRG.java b/chapter21/src/main/java/com/seaofnodes/simple/codegen/LRG.java
index db5a3242..2e56e050 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/codegen/LRG.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/codegen/LRG.java
@@ -62,6 +62,8 @@ public class LRG {
     // Adjacent Live Range neighbors.  Only valid during coloring
     Ary<LRG> _adj;
 
+    public int nadj() { return _adj==null ? 0 : _adj._len; }
+
     void addNeighbor(LRG lrg) {
         if( _adj==null ) _adj = new Ary<>(LRG.class);
         _adj.push(lrg);
@@ -80,7 +82,7 @@ public class LRG {
     }
 
     // More registers than neighbors
-    boolean lowDegree() { return (_adj==null ? 0 : _adj._len) < _mask.size(); }
+    boolean lowDegree() { return nadj() < _mask.size(); }
 
     LRG( short lrg ) { _lrg = lrg; _reg = -1; }
 
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegAlloc.java b/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegAlloc.java
index 9c0f5f51..ceb75d64 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegAlloc.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegAlloc.java
@@ -288,7 +288,7 @@ public class RegAlloc {
             // all uses by class to split
             for( int j=0; j < def._outputs._len; j++ ) {
                 Node use = def._outputs.at(j);
-                if( use instanceof MachNode mach ) {
+                if( use instanceof MachNode mach && use!=split ) {
                     // Check all use inputs for n, in case there's several
                     for( int i = 1; i < use.nIns(); i++ )
                         // Find a def input, and check register class
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegMask.java b/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegMask.java
index df53c7ca..88ce8627 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegMask.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegMask.java
@@ -119,25 +119,3 @@ public class RegMask {
     }
 }
 
-// Mutable regmask(writable)
-class RegMaskRW extends RegMask {
-    public RegMaskRW(long x, long y) { super(x,y);  }
-    // clears bit at position r. Returns true if the mask is still not empty.
-    public boolean clr(int r) {
-        if( r < 64 ) _bits0 &= ~(1L<<(r   ));
-        else         _bits1 &= ~(1L<<(r-64));
-        return _bits0!=0 || _bits1!=0;
-    }
-    @Override RegMaskRW and( RegMask mask ) {
-        if( mask==null ) return this;
-        _bits0 &= mask._bits0;
-        _bits1 &= mask._bits1;
-        return this;
-    }
-    @Override RegMaskRW sub( RegMask mask ) {
-        if( mask==null ) return this;
-        _bits0 &= ~mask._bits0;
-        _bits1 &= ~mask._bits1;
-        return this;
-    }
-}
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegMaskRW.java b/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegMaskRW.java
new file mode 100644
index 00000000..6fa5344f
--- /dev/null
+++ b/chapter21/src/main/java/com/seaofnodes/simple/codegen/RegMaskRW.java
@@ -0,0 +1,31 @@
+package com.seaofnodes.simple.codegen;
+
+// Mutable regmask(writable)
+public class RegMaskRW extends RegMask {
+    public RegMaskRW(long x, long y) { super(x,y);  }
+    // clears bit at position r. Returns true if the mask is still not empty.
+    public boolean clr(int r) {
+        if( r < 64 ) _bits0 &= ~(1L<<(r   ));
+        else         _bits1 &= ~(1L<<(r-64));
+        return _bits0!=0 || _bits1!=0;
+    }
+    @Override RegMaskRW and( RegMask mask ) {
+        if( mask==null ) return this;
+        _bits0 &= mask._bits0;
+        _bits1 &= mask._bits1;
+        return this;
+    }
+    @Override RegMaskRW sub( RegMask mask ) {
+        if( mask==null ) return this;
+        _bits0 &= ~mask._bits0;
+        _bits1 &= ~mask._bits1;
+        return this;
+    }
+    public RegMaskRW or( RegMask mask ) {
+        if( mask!=null ) {
+            _bits0 |= mask._bits0;
+            _bits1 |= mask._bits1;
+        }
+        return this;
+    }
+}
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/node/cpus/riscv/RetRISC.java b/chapter21/src/main/java/com/seaofnodes/simple/node/cpus/riscv/RetRISC.java
index e04d3691..87927242 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/node/cpus/riscv/RetRISC.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/node/cpus/riscv/RetRISC.java
@@ -41,7 +41,7 @@ public class RetRISC extends ReturnNode implements MachNode {
             // Prints return reg (either A0 or FA0), RPC (always R1) and then
             // the callee-save registers.
             for( int i=2; i<nIns(); i++ )
-                sb.p(code.reg(in(i))).p("  ");
+                sb.p(in(i)==null ? "---" : code.reg(in(i))).p("  ");
 
         // Post-allocation, if we did not get the expected return register, print what we got
         else if( code._regAlloc.regnum(rpc()) != riscv.RPC )