Forward-port allocator bug fixes and test support through ch25

Improved spilling

8 files changed, 289 insertions, 15 deletions

diff --git a/chapter23/src/test/java/com/seaofnodes/simple/Chapter20Test.java b/chapter23/src/test/java/com/seaofnodes/simple/Chapter20Test.java
index 8ce02220..15addc7b 100644
--- a/chapter23/src/test/java/com/seaofnodes/simple/Chapter20Test.java
+++ b/chapter23/src/test/java/com/seaofnodes/simple/Chapter20Test.java
@@ -1,5 +1,7 @@
 package com.seaofnodes.simple;
 
+import com.seaofnodes.simple.codegen.RegAllocTestSupport.CheckedCodeGen;
+
 
 import com.seaofnodes.simple.codegen.CodeGen;
 import com.seaofnodes.simple.print.ASMPrinter;
@@ -29,6 +31,14 @@ return f(s);
     }
 
 
+    @Test public void testAllocatorMasks() { com.seaofnodes.simple.codegen.RegAllocTestSupport.masks(); }
+    @Test public void testAllocatorUnion() { com.seaofnodes.simple.codegen.RegAllocTestSupport.union(); }
+    @Test public void testAllocatorCopyClobber() throws Exception { com.seaofnodes.simple.codegen.RegAllocTestSupport.copyClobber(); }
+    @Test public void testAllocatorCommutativePhi() { com.seaofnodes.simple.codegen.RegAllocTestSupport.commutativePhi(); }
+    @Test public void testAllocatorKills() { com.seaofnodes.simple.codegen.RegAllocTestSupport.killWithoutResult(); }
+    @Test public void testAllocatorDependencies() { com.seaofnodes.simple.codegen.RegAllocTestSupport.nullUseMask(); }
+    @Test public void testAllocatorCloneClass() { com.seaofnodes.simple.codegen.RegAllocTestSupport.cloneRegisterClass(); }
+
     @Test public void testPrintingRegisters() throws Exception {
         com.seaofnodes.simple.codegen.PrintRegTestSupport.check();
     }
@@ -43,7 +53,7 @@ return f(s);
     }
 
     static void testCPU( String src, String cpu, String os, int spills, String stop ) {
-        CodeGen code = new CodeGen(src);
+        CodeGen code = new CheckedCodeGen(src);
         code.driver(CodeGen.Phase.RegAlloc,cpu,os);
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
@@ -88,7 +98,7 @@ val sqrt = { int x ->
 int cast_int = arg+2;
 return sqrt(arg) + sqrt(cast_int);
 """;
-        testCPU(src,"x86_64_v2", "Win64"  ,55,null);
+        testCPU(src,"x86_64_v2", "Win64"  ,48,null);
         testCPU(src,"riscv"    , "SystemV",19,null);
         testCPU(src,"arm"      , "SystemV",19,null);
     }
diff --git a/chapter23/src/test/java/com/seaofnodes/simple/Chapter21Test.java b/chapter23/src/test/java/com/seaofnodes/simple/Chapter21Test.java
index db8e398a..9e73a9c0 100644
--- a/chapter23/src/test/java/com/seaofnodes/simple/Chapter21Test.java
+++ b/chapter23/src/test/java/com/seaofnodes/simple/Chapter21Test.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple;
 
+import com.seaofnodes.simple.codegen.RegAllocTestSupport.CheckedCodeGen;
 import com.seaofnodes.simple.codegen.CodeGen;
 import com.seaofnodes.simple.node.cpus.arm.arm;
 import com.seaofnodes.simple.node.cpus.riscv.riscv;
@@ -12,6 +13,54 @@ import org.junit.Test;
 import static org.junit.Assert.*;
 
 public class Chapter21Test {
+    @Test public void testCoalescing() { com.seaofnodes.simple.codegen.RegAllocTestSupport.coalescing(); }
+
+    @Test public void testNarrowStores() throws IOException {
+        for( String type : new String[]{"i8","u8","i16","u16"} ) {
+            String src = "struct S { "+type+" x; }; S !s = new S; s.x = arg; return 0;";
+            CodeGen code = new CodeGen(src).driver("riscv","SystemV",null);
+            int stores=0;
+            for( var bb : code._cfg )
+                for( var node : bb.outs() )
+                    if( node instanceof com.seaofnodes.simple.node.cpus.riscv.StoreRISC st ) {
+                        stores++;
+                        assertEquals("Byte/short stores have no FP encoding",-1,st.regmap(4).nextReg((short)31));
+                    }
+            assertEquals(1,stores);
+            byte[] image = new byte[1<<20];
+            byte[] bits = code._encoding.bits();
+            System.arraycopy(bits,0,image,0,bits.length);
+            EvalRisc5 cpu = new EvalRisc5(image,1<<16);
+            cpu.regs[riscv.A0] = 0x8765;
+            assertEquals(0,cpu.step(100));
+            assertEquals(type.endsWith("8") ? 0x65 : 0x8765,
+                         type.endsWith("8") ? cpu.ld1z(1<<16) : cpu.ld2z(1<<16));
+            code = new CodeGen(src).driver(CodeGen.Phase.Encoding,"x86_64_v2",TestC.CALL_CONVENTION);
+            stores=0;
+            for( var bb : code._cfg )
+                for( var node : bb.outs() )
+                    if( node instanceof com.seaofnodes.simple.node.cpus.x86_64_v2.StoreX86 st ) {
+                        stores++;
+                        assertEquals("Byte/short stores have no XMM encoding",-1,st.regmap(4).nextReg((short)15));
+                    }
+            assertEquals(1,stores);
+        }
+    }
+
+    @Test public void testNativeExitStatus() throws IOException {
+        Path source = Path.of("build/objs/nativeExit.c");
+        Files.createDirectories(source.getParent());
+        Files.writeString(source,"int main() { return 7; }\n");
+        try {
+            TestC.gcc(source.toString(),null,null,false,
+                      "build/objs/nativeExit"+(TestC.OS.startsWith("Windows") ? ".exe" : ""));
+        } catch( AssertionError error ) {
+            assertTrue(error.getMessage(),error.getMessage().contains("Program exit status"));
+            return;
+        }
+        fail("A failing native program must fail the test, even with empty stdout");
+    }
+
     @Test public void testArmSubtractRegisters() {
         EvalArm64 cpu = new EvalArm64(new byte[16],16);
         cpu.st4(0,0xCB020020); // SUB X0,X1,X2, no shift or flag update.
@@ -64,7 +113,7 @@ public class Chapter21Test {
     }
 
     static void testCPU( String src, String cpu, String os, int spills, String stop ) {
-        CodeGen code = new CodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
+        CodeGen code = new CheckedCodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
         if( spills != -1 )
@@ -163,11 +212,11 @@ public class Chapter21Test {
         String sprimes = sb.p("]").toString();
 
         // Compile, link against native C; expect the above string of primes to be printed out by C
-        TestC.run("sieve",sprimes, 257);
+        TestC.run("sieve",sprimes, 186);
 
         // Evaluate on RISC5 emulator; expect return of an array of primes in
         // the simulated heap.
-        EvalRisc5 R5 = TestRisc5.build("sieve", 100, 160, false);
+        EvalRisc5 R5 = TestRisc5.build("sieve", 100, 92, false);
         int trap = R5.step(10000);
         assertEquals(0,trap);
         // Return register A0 holds sieve(100)
@@ -179,7 +228,7 @@ public class Chapter21Test {
 
         // Evaluate on ARM5 emulator; expect return of an array of primes in
         // the simulated heap.
-        EvalArm64 A5 = TestArm64.build("sieve", 100, 160, false);
+        EvalArm64 A5 = TestArm64.build("sieve", 100, 94, false);
         int trap_arm = A5.step(10000);
         assertEquals(0, trap_arm);
         int ary_arm = (int)A5.regs[arm.X0];
@@ -258,7 +307,7 @@ public class Chapter21Test {
         // than what Win64 allows - so Win64 gets a lot more spills here.
         String arg_count = "191.000000\n";
         TestC.run("arg_count", arg_count,
-                  TestC.CALL_CONVENTION.equals("Win64") ? 42 : 15);
+                  TestC.CALL_CONVENTION.equals("Win64") ? 32 : 15);
 
 
         EvalRisc5 R5 = TestRisc5.build("no_stack_arg_count", 0, 0, false);
diff --git a/chapter23/src/test/java/com/seaofnodes/simple/Chapter22Test.java b/chapter23/src/test/java/com/seaofnodes/simple/Chapter22Test.java
index f6410b6a..d6f31ff6 100644
--- a/chapter23/src/test/java/com/seaofnodes/simple/Chapter22Test.java
+++ b/chapter23/src/test/java/com/seaofnodes/simple/Chapter22Test.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple;
 
+import com.seaofnodes.simple.codegen.RegAllocTestSupport.CheckedCodeGen;
 import com.seaofnodes.simple.codegen.CodeGen;
 import java.io.IOException;
 import java.nio.file.Files;
@@ -23,7 +24,7 @@ public class Chapter22Test {
     }
 
     static CodeGen testCPU( String src, String cpu, String os, int spills, String stop ) {
-        CodeGen code = new CodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
+        CodeGen code = new CheckedCodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
         if( spills != -1 )
diff --git a/chapter23/src/test/java/com/seaofnodes/simple/Chapter23Test.java b/chapter23/src/test/java/com/seaofnodes/simple/Chapter23Test.java
index 45acc62a..4bb8ded0 100644
--- a/chapter23/src/test/java/com/seaofnodes/simple/Chapter23Test.java
+++ b/chapter23/src/test/java/com/seaofnodes/simple/Chapter23Test.java
@@ -1,4 +1,6 @@
 package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.codegen.RegAllocTestSupport.CheckedCodeGen;
 import com.seaofnodes.simple.node.*;
 import com.seaofnodes.simple.type.*;
 
@@ -90,7 +92,7 @@ var apply = { i64 x, { i64 -> u32 } fcn ->
     }
 
     static CodeGen testCPU( String src, String cpu, String os, int spills, String stop ) {
-        CodeGen code = new CodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
+        CodeGen code = new CheckedCodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
         if( spills != -1 )
diff --git a/chapter23/src/test/java/com/seaofnodes/simple/TestArm64.java b/chapter23/src/test/java/com/seaofnodes/simple/TestArm64.java
index 5d7d1361..38fd2a85 100644
--- a/chapter23/src/test/java/com/seaofnodes/simple/TestArm64.java
+++ b/chapter23/src/test/java/com/seaofnodes/simple/TestArm64.java
@@ -1,5 +1,7 @@
 package com.seaofnodes.simple;
 
+import com.seaofnodes.simple.codegen.RegAllocTestSupport.CheckedCodeGen;
+
 
 import com.seaofnodes.simple.codegen.CodeGen;
 import com.seaofnodes.simple.node.cpus.arm.arm;
@@ -21,7 +23,7 @@ public class TestArm64 {
     public static EvalArm64 build( String dir, String file, int arg, int spills, boolean print ) throws IOException {
         // Compile and export Simple
         String src = Files.readString(Path.of(dir+"/"+file+".smp"));
-        CodeGen code = new CodeGen(src).driver("arm", "SystemV",null);
+        CodeGen code = new CheckedCodeGen(src).driver("arm", "SystemV",null);
         if( print ) { code.print_as_hex(); System.out.print(code.asm()); }
 
         // Allocation quality not degraded
diff --git a/chapter23/src/test/java/com/seaofnodes/simple/TestC.java b/chapter23/src/test/java/com/seaofnodes/simple/TestC.java
index dbe9f02f..6edde562 100644
--- a/chapter23/src/test/java/com/seaofnodes/simple/TestC.java
+++ b/chapter23/src/test/java/com/seaofnodes/simple/TestC.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple;
 
+import com.seaofnodes.simple.codegen.RegAllocTestSupport.CheckedCodeGen;
 import com.seaofnodes.simple.codegen.CodeGen;
 import com.seaofnodes.simple.type.TypeInteger;
 import com.seaofnodes.simple.util.Ary;
@@ -58,7 +59,7 @@ public abstract class TestC {
         String obj = bin+".o";
         String exe = OS.startsWith("Windows") ? bin+".exe" : bin;
         // Compile simple, emit ELF
-        CodeGen code = new CodeGen(src, arg).driver( CPU_PORT, simple_conv, obj);
+        CodeGen code = new CheckedCodeGen(src, arg).driver( CPU_PORT, simple_conv, obj);
 
         String result = gcc(obj, c_conv, cfile, false, exe );
         assertEquals(expected,result);
@@ -113,10 +114,9 @@ public abstract class TestC {
         ProcessBuilder smp = new ProcessBuilder(args);
         if( stdin ) smp.redirectInput(ProcessBuilder.Redirect.INHERIT);
         Process p = smp.start();
-        try { exit = (byte)p.waitFor(); } catch( InterruptedException e ) { throw new IOException("interrupted"); }
+        try { exit = p.waitFor(); } catch( InterruptedException e ) { throw new IOException("interrupted"); }
         result = new String(p.getInputStream().readAllBytes());
-        if( exit!=0 )
-            System.err.println("exec exit code: "+exit);
+        assertEquals("Program exit status",0,exit);
         return result;
     }
 }
diff --git a/chapter23/src/test/java/com/seaofnodes/simple/TestRisc5.java b/chapter23/src/test/java/com/seaofnodes/simple/TestRisc5.java
index 041ed833..cb1c95e9 100644
--- a/chapter23/src/test/java/com/seaofnodes/simple/TestRisc5.java
+++ b/chapter23/src/test/java/com/seaofnodes/simple/TestRisc5.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple;
 
+import com.seaofnodes.simple.codegen.RegAllocTestSupport.CheckedCodeGen;
 import com.seaofnodes.simple.codegen.CodeGen;
 import com.seaofnodes.simple.node.FunNode;
 import com.seaofnodes.simple.node.Node;
@@ -20,7 +21,7 @@ public abstract class TestRisc5 {
     public static EvalRisc5 build( String dir, String file, String main, int arg, int spills, boolean print ) throws IOException {
         // Compile and export Simple
         String src = Files.readString(Path.of(dir+"/"+file+".smp"));
-        CodeGen code = new CodeGen(src).driver("riscv", "SystemV",null);
+        CodeGen code = new CheckedCodeGen(src).driver("riscv", "SystemV",null);
         if( print ) { code.print_as_hex(); System.out.print(code.asm()); }
 
         // Allocation quality not degraded
diff --git a/chapter23/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java b/chapter23/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java
new file mode 100644
index 00000000..b2d14a02
--- /dev/null
+++ b/chapter23/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java
@@ -0,0 +1,209 @@
+package com.seaofnodes.simple.codegen;
+
+import com.seaofnodes.simple.node.*;
+import com.seaofnodes.simple.node.cpus.x86_64_v2.x86_64_v2;
+import com.seaofnodes.simple.type.TypeInteger;
+import static org.junit.Assert.*;
+
+// Small scheduled machine graphs isolate register constraints from peepholes.
+public class RegAllocTestSupport {
+    private static final RegMask A = new RegMask(0), B = new RegMask(1);
+    private static class Op extends MachConcreteNode {
+        final RegMask _def, _use, _kill;
+        final boolean _clone;
+        Op(RegMask def, RegMask use, RegMask kill, boolean clone, Node... ins) {
+            super(ins); _def=def; _use=use; _kill=kill; _clone=clone; _type=TypeInteger.BOT;
+        }
+        @Override public String op() { return "testOp"; }
+        @Override public RegMask outregmap() { return _def; }
+        @Override public RegMask regmap(int i) { return _use; }
+        @Override public RegMask killmap() { return _kill; }
+        @Override public boolean isClone() { return _clone; }
+        @Override public Node copy() { return new Op(_def,_use,_kill,_clone,(Node)null); }
+        @Override public void encoding(Encoding enc) { throw new AssertionError(); }
+    }
+    private static CodeGen graph() {
+        CodeGen code = new CodeGen("");
+        code._mach = new x86_64_v2(code);
+        code._cfg.add(code._start);
+        return code;
+    }
+
+    public static void masks() {
+        for( int reg : new int[]{0,63,64,65,127} ) {
+            RegMask mask = new RegMask(reg);
+            assertEquals(reg,mask.firstReg());
+            assertEquals(1,mask.size());
+        }
+        assertEquals(-1,new RegMask(0L).firstReg());
+        assertFalse(new RegMask(0L).size1());
+        RegMask boundary = new RegMask(Long.MIN_VALUE,Long.MIN_VALUE|1);
+        assertEquals(64,boundary.nextReg((short)63));
+        assertEquals(127,boundary.nextReg((short)64));
+        assertEquals(-1,boundary.nextReg((short)127));
+    }
+
+    public static void union() {
+        CodeGen code = graph();
+        Op use = new Op(null,B,null,false,code._start);
+        LRG a = new LRG((short)1), b = new LRG((short)2);
+        a._mask = new RegMask(3L);
+        b._mask = new RegMask(6L);
+        b.machUse(use,(short)2,true);
+        LRG both = a.union(b);
+        assertNotNull(both._mask);
+        assertEquals(1,both._mask.firstReg());
+        assertEquals(1,both._mask.size());
+        assertSame(use,both._machUse);
+        assertEquals(2,both._uidx);
+    }
+
+    public static void killWithoutResult() {
+        CodeGen code = graph();
+        Op def = new Op(A,null,null,false,code._start);
+        new Op(null,null,A,false,code._start); // Clobbers A, produces no value.
+        new Op(null,A,null,false,code._start,def);
+        RegAlloc alloc = new RegAlloc(code);
+        assertTrue(BuildLRG.run(0,alloc));
+        assertFalse("A live value cannot survive a register kill",IFG.build(0,alloc));
+    }
+
+    public static void nullUseMask() {
+        CodeGen code = graph();
+        Op def = new Op(A,null,null,false,code._start);
+        new Op(null,null,null,false,code._start,def); // Scheduling dependency only.
+        RegAlloc alloc = new RegAlloc(code);
+        assertTrue(BuildLRG.run(0,alloc));
+        assertTrue(IFG.build(0,alloc));
+    }
+
+    public static void cloneRegisterClass() {
+        for( RegMask required : new RegMask[]{B,new RegMask(6L)} ) {
+            CodeGen code = graph();
+            Op def = new Op(A,null,null,true,code._start);
+            Op use = new Op(null,required,null,false,code._start,def);
+            Op use2 = new Op(null,required,null,false,code._start,def);
+            RegAlloc alloc = new RegAlloc(code);
+            alloc.regAlloc(); // Re-cloning an A-only value cannot satisfy B/C uses.
+            assertEquals(0,alloc.regnum(def));
+            assertTrue(required.test(alloc.regnum(use.in(1))));
+            assertTrue(required.test(alloc.regnum(use2.in(1))));
+            assertTrue(use.in(1) instanceof SplitNode);
+        }
+    }
+
+    public static void commutativePhi() {
+        CodeGen code = graph();
+        Op a = new Op(A,null,null,false,code._start);
+        Op b = new Op(A,null,null,false,code._start);
+        Op add = new Op(A,A,null,false,code._start,a,b) {
+            @Override public boolean commutes() { return true; }
+        };
+        RegionNode region = new RegionNode(null,code._start,code._start);
+        new PhiNode("sum",TypeInteger.BOT,region,add,a);
+        code._cfg.add(region);
+        assertTrue(BuildLRG.run(0,new RegAlloc(code)));
+    }
+
+    // Check the scheduled graph before encoding adds untyped branches or rewrites tail calls.
+    public static class CheckedCodeGen extends CodeGen {
+        public CheckedCodeGen(String src) { super(src); }
+        public CheckedCodeGen(String src, TypeInteger arg) { super(src,arg); }
+        @Override public CodeGen regAlloc() {
+            super.regAlloc();
+            checkRegisters(this);
+            return this;
+        }
+    }
+
+    public static void checkRegisters(CodeGen code) {
+        assertTrue(code._regAlloc.verifyFunctionLocalEdges());
+        for( CFGNode bb : code._cfg )
+            for( Node n : bb._outputs ) {
+                if( n instanceof MachNode mach ) {
+                    if( code._regAlloc.regnum(n)>=0 && mach.outregmap()!=null )
+                        assertTrue(n.getClass().getSimpleName()+"#"+n._nid,code._regAlloc.regnum(n)>=0 && mach.outregmap().test(code._regAlloc.regnum(n)));
+                    for( int i=n instanceof ParmNode ? 2 : 1; i<n.nIns(); i++ )
+                        if( n.in(i)!=null && code._regAlloc.regnum(n.in(i))>=0 && mach.regmap(i)!=null )
+                            assertTrue(n.getClass().getSimpleName()+"#"+n._nid+" input "+i,code._regAlloc.regnum(n.in(i))>=0 && mach.regmap(i).test(code._regAlloc.regnum(n.in(i))));
+                    if( mach.twoAddress()!=0 )
+                        assertEquals(code._regAlloc.regnum(n),code._regAlloc.regnum(n.in(mach.twoAddress())));
+                }
+                if( n instanceof PhiNode && code._regAlloc.regnum(n)>=0 )
+                    for( int i=n instanceof ParmNode ? 2 : 1; i<n.nIns(); i++ )
+                        assertEquals(code._regAlloc.regnum(n),code._regAlloc.regnum(n.in(i)));
+            }
+    }
+
+    public static void copyClobber() throws Exception {
+        for( boolean killed : new boolean[]{false,true} ) {
+            CodeGen code = graph();
+            RegAlloc alloc = new RegAlloc(code);
+            Op def = new Op(A,null,null,false,code._start);
+            alloc.newLRG(def)._reg=0;
+            SplitNode hi = code._mach.split("test",(byte)0,null);
+            hi.setDef(0,code._start); hi.setDef(1,def);
+            alloc.newLRG(hi)._reg=1;
+            new Op(null,null,killed ? A : null,false,code._start);
+            SplitNode lo = code._mach.split("test",(byte)0,null);
+            lo.setDef(0,code._start); lo.setDef(1,hi);
+            alloc.newLRG(lo)._reg=0;
+            Op use = new Op(null,A,null,false,code._start,lo);
+            var post = RegAlloc.class.getDeclaredMethod("postColor");
+            post.setAccessible(true); post.invoke(alloc);
+            assertSame(killed ? lo : def,use.in(1));
+        }
+        CodeGen pre = graph();
+        RegAlloc uncolored = new RegAlloc(pre);
+        Op def0 = new Op(A,null,null,false,pre._start);
+        uncolored.newLRG(def0)._mask=A;
+        Op fixed = new Op(A,null,null,false,pre._start);
+        uncolored.newLRG(fixed)._mask=A;
+        SplitNode copy = pre._mach.split("test",(byte)0,null);
+        copy.setDef(0,pre._start); copy.setDef(1,def0);
+        assertFalse("A fixed definition clobbers even before coloring",uncolored.sameBlockNoClobber(copy));
+    }
+
+    public static void coalescing() {
+        // Merge, incompatible masks, interference, capacity, and adjacency remapping.
+        for( int kind=0; kind<5; kind++ ) {
+            CodeGen code = graph();
+            RegAlloc alloc = new RegAlloc(code);
+            Op def = new Op(new RegMask(3L),null,null,false,code._start);
+            SplitNode copy = code._mach.split("test",(byte)0,null);
+            copy.setDef(0,code._start); copy.setDef(1,def);
+            Op use = new Op(null,new RegMask(3L),null,false,code._start,copy);
+            LRG from = alloc.newLRG(def), to = alloc.newLRG(copy);
+            from._mask = kind==1 ? A : new RegMask(3L);
+            to._mask = kind==1 ? B : new RegMask(3L);
+            from.machDef(def,false); from.machUse(copy,(short)1,false);
+            to.machDef(copy,false); to.machUse(use,(short)1,false);
+            LRG left = new LRG((short)100), right = new LRG((short)101);
+            if( kind==2 ) { from.addNeighbor(to); to.addNeighbor(from); }
+            if( kind>=3 ) {
+                from.addNeighbor(left); left.addNeighbor(from);
+                if( kind==3 ) { to.addNeighbor(right); right.addNeighbor(to); }
+                else { to.addNeighbor(left); left.addNeighbor(to); }
+            }
+            int fcnt=from.nadj(), tcnt=to.nadj();
+            assertTrue(Coalesce.coalesce(0,alloc));
+            if( kind==0 || kind==4 ) {
+                assertSame(def,use.in(1));
+                assertSame(alloc.lrg(def),alloc.lrg(copy));
+                assertSame(use,alloc.lrg(def)._machUse);
+                assertEquals(1,alloc.lrg(def)._uidx);
+                if( kind==4 ) {
+                    assertEquals(1,left.nadj());
+                    assertSame(alloc.lrg(def),left._adj.at(0));
+                    assertSame(left,alloc.lrg(def)._adj.at(0));
+                }
+            } else {
+                assertSame(copy,use.in(1));
+                assertNotSame(alloc.lrg(def),alloc.lrg(copy));
+                assertEquals(fcnt,from.nadj());
+                assertEquals(tcnt,to.nadj());
+            }
+        }
+    }
+
+}