#57 WIP sequence parallel copies

Author: dibyendumajumdar

optvm/src/main/java/com/compilerprogramming/ezlang/compiler/ExitSSA2.java

@@ -120,7 +120,122 @@ private void removePhis() {
     }
 
     private void sequenceParallelCopies() {
+        for (var block: function.getBlocks()) {
+            var pcopy = parallelCopies.get(block);
+            if (pcopy.pCopyBegin != null)
+                sequenceParallelCopy(block,pcopy.pCopyBegin);
+            if (pcopy.pCopyEnd != null)
+                sequenceParallelCopy(block,pcopy.pCopyEnd);
+        }
+    }
+
+    private void replaceInstruction(BasicBlock block, Instruction.ParallelCopyInstruction pcopy, ArrayList<Instruction> instructions) {
+        block.replaceInstruction(pcopy, instructions);
+    }
+
+    static final class Copy {
+        Operand src;
+        Operand dest;
+        boolean removed = false;
+
+        public Copy(Operand src, Operand dest) {
+            this.src = src;
+            this.dest = dest;
+        }
+    }
+
+    List<Copy> getCopies(Instruction.ParallelCopyInstruction pcopy) {
+        List<Copy> copies = new ArrayList<>();
+        for (int i = 0; i < pcopy.sourceOperands.size(); i++) {
+            var src = pcopy.sourceOperands.get(i);
+            var dest = pcopy.destOperands.get(i);
+            if (src instanceof Operand.RegisterOperand srcR && dest instanceof Operand.RegisterOperand destR) {
+                if (srcR.reg.id == destR.reg.id)
+                    continue;
+            }
+            copies.add(new Copy(src,dest));
+        }
+        return copies;
+    }
+
+    private void sequenceParallelCopy(BasicBlock block, Instruction.ParallelCopyInstruction pcopy) {
+        var copyInstructions = new ArrayList<Instruction>();
+        var copies = getCopies(pcopy);
+
+        while (copies.size() > 0) {
+            boolean progress = false;
+
+            for (var copy: copies) {
+                boolean cycle = false;
+                for (int i = 0; i < copies.size(); i++) {
+                    if (copy.removed == true)
+                        continue;
+                    if (copy.src.equals(copies.get(i).dest)) {
+                        cycle = true;
+                        break;
+                    }
+                }
+                if (!cycle) {
+                    copyInstructions.add(new Instruction.Move(copy.src,copy.dest));
+                    copy.removed = true;
+                    progress = true;
+                }
+            }
+
+            copies.removeIf(c->c.removed);
+            if (progress)
+                continue;
+
+            var copy = copies.removeFirst();
+            var temp = new Operand.RegisterOperand(function.registerPool.newTempReg(copy.src.type));
+            copyInstructions.add(new Instruction.Move(copy.src,temp));
+            copies.add(new Copy(copy.dest,temp));
+        }
+        replaceInstruction(block,pcopy,copyInstructions);
+    }
 
+    private void sequenceParallelCopyX(BasicBlock block, Instruction.ParallelCopyInstruction pcopy) {
+        var copyInstructions = new ArrayList<Instruction>();
+        var ready = new ArrayList<Operand>();
+        var toDo = new ArrayList<Operand>();
+        var directPred = new HashMap<Operand,Operand>();
+        var loc = new HashMap<Operand,Operand>();
+        for (int i = 0; i <pcopy.sourceOperands.size(); i++) {
+            var a = pcopy.sourceOperands.get(i);
+            var b = pcopy.destOperands.get(i);
+            if (a.equals(b))
+                continue;
+            loc.put(a,a);
+            directPred.put(b,a);
+            toDo.add(b);
+        }
+        for (int i = 0; i <pcopy.sourceOperands.size(); i++) {
+            var a = pcopy.sourceOperands.get(i);
+            var b = pcopy.destOperands.get(i);
+            if (a == b)
+                continue;
+            if (loc.get(b) == null)
+                ready.add(b);
+        }
+        while (!toDo.isEmpty()) {
+            while (!ready.isEmpty()) {
+                var b = ready.removeLast();
+                var a = directPred.get(b);
+                var c = loc.get(a);
+                copyInstructions.add(new Instruction.Move(c,b));
+                loc.put(a,b);
+                if (a == c && directPred.get(a) != null)
+                    ready.add(a);
+            }
+            var b = toDo.removeLast();
+            if (b == loc.get(directPred.get(b))) {
+                var n = new Operand.RegisterOperand(function.registerPool.newTempReg(b.type));
+                copyInstructions.add(new Instruction.Move(b,n));
+                loc.put(b,n);
+                ready.add(b);
+            }
+        }
+        replaceInstruction(block,pcopy,copyInstructions);
     }
 
     static final class PCopy {