From a996996a1ad776089a4cb9cbf7744f5f4e8dde6d Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Wed, 30 Sep 2026 16:41:07 -0700
Subject: Forward port mem stuff to ch21

Also a minor reg-alloc improvement for BrainFuck, ported up to ch25
---
 .../java/com/seaofnodes/simple/Chapter20Test.java  |  2 +-
 .../java/com/seaofnodes/simple/Chapter21Test.java  |  3 ++-
 .../simple/codegen/RegAllocTestSupport.java        | 25 ++++++++++++++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

(limited to 'chapter25/src/test/java/com')

diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java
index 5ea198ef..ce604cf1 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java
@@ -225,7 +225,7 @@ val _hashCodeString = { String self ->
 """;
         testCPU(src,"x86_64_v2", "SystemV",21,null);
         testCPU(src,"riscv"    , "SystemV",10,null);
-        testCPU(src,"arm"      , "SystemV",10,null);
+        testCPU(src,"arm"      , "SystemV",8,null);
     }
 
     @Test
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java
index 88e963c0..b88e8af9 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java
@@ -169,6 +169,7 @@ public class Chapter21Test {
 
 
     @Test public void testCoalescing() { com.seaofnodes.simple.codegen.RegAllocTestSupport.coalescing(); }
+    @Test public void testCopyForward() throws Exception { com.seaofnodes.simple.codegen.RegAllocTestSupport.copyForward(); }
 
     @Test public void testArmSubtractRegisters() {
         EvalArm64 cpu = new EvalArm64(new byte[16],16);
@@ -339,7 +340,7 @@ val _hashCodeString = { String self ->
 """;
         testCPU(src,"x86_64_v2", "SystemV",21,null);
         testCPU(src,"riscv"    , "SystemV",10,null);
-        testCPU(src,"arm"      , "SystemV",10,null);
+        testCPU(src,"arm"      , "SystemV",8,null);
     }
 
     @Test public void testStringExport() throws IOException {
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java b/chapter25/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java
index 6c6b9ad5..873578c2 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java
@@ -251,6 +251,31 @@ public class RegAllocTestSupport {
         }
     }
 
+    public static void copyForward() throws Exception {
+        // Forwarding, fixed operand, two-address tie, intervening clobber,
+        // another user, and a scheduling-only edge.
+        for( int kind=0; kind<6; kind++ ) {
+            CodeGen code = graph();
+            RegAlloc alloc = new RegAlloc(code);
+            Op def = new Op(A,null,null,false,code._start);
+            alloc.newLRG(def,null)._reg=0;
+            SplitNode copy = code._mach.split(null,"test",(byte)0);
+            copy.setDef(0,code._start); copy.setDef(1,def);
+            alloc.newLRG(copy,null)._reg=1;
+            if( kind==3 ) new Op(null,null,A,false,code._start);
+            int twoAddress = kind==2 ? 1 : 0;
+            RegMask mask = kind==1 ? B : kind==5 ? null : new RegMask(3L);
+            Op use = new Op(null,mask,null,false,code._start,copy) {
+                @Override public int twoAddress() { return twoAddress; }
+            };
+            if( kind==4 ) new Op(null,B,null,false,code._start,copy);
+            var post = RegAlloc.class.getDeclaredMethod("postColor");
+            post.setAccessible(true); post.invoke(alloc);
+            assertSame("copy case "+kind,kind==0 ? def : copy,use.in(1));
+            assertEquals(kind==0 ? 0 : 1,alloc._spills);
+        }
+    }
+
     public static void coalescing() {
         // Merge, incompatible masks, interference, capacity, and adjacency remapping.
         for( int kind=0; kind<5; kind++ ) {
-- 
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