Fix bug - instruction.block not being set

Author: dibyendumajumdar

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

@@ -98,6 +98,14 @@ public void add(Instruction instruction) {
         instructions.add(instruction);
         instruction.block = this;
     }
+    public void add(int pos, Instruction instruction) {
+        instructions.add(pos, instruction);
+        instruction.block = this;
+    }
+    public void update(int pos, Instruction instruction) {
+       instructions.set(pos, instruction);
+       instruction.block = this;
+    }
     public void deleteInstruction(Instruction instruction) {
         instructions.remove(instruction);
     }
@@ -129,8 +137,7 @@ public void insertPhiFor(Register var) {
         for (int i = 0; i < predecessors.size(); i++)
             inputs.add(var);
         Instruction.Phi phi = new Instruction.Phi(var, inputs);
-        instructions.add(0, phi);
-        phi.block = this;
+        add(0, phi);
     }
     public List<Instruction.Phi> phis() {
         List<Instruction.Phi> list = new ArrayList<>();

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

@@ -200,7 +200,7 @@ private void insertAtEnd(BasicBlock bb, Instruction i) {
         // Last instruction is a branch - so new instruction will
         // go before that
         int pos = bb.instructions.size()-1;
-        bb.instructions.add(pos, i);
+        bb.add(pos, i);
     }
 
     private void insertAfterPhi(BasicBlock bb, Register phiDef, Instruction newInst) {
@@ -218,7 +218,7 @@ private void insertAfterPhi(BasicBlock bb, Register phiDef, Instruction newInst)
         if (insertionPos < 0) {
             throw new IllegalStateException();
         }
-        bb.instructions.add(insertionPos, newInst);
+        bb.add(insertionPos, newInst);
     }
 
     /* Insert a copy from dest to new temp at end of BB, and return temp */

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

@@ -31,13 +31,13 @@ public abstract class Instruction {
     protected Operand[] uses;
     public BasicBlock block;
 
-    public Instruction(int opcode, Operand... uses) {
+    protected Instruction(int opcode, Operand... uses) {
         this.opcode = opcode;
         this.def = null;
         this.uses = new Operand[uses.length];
         System.arraycopy(uses, 0, this.uses, 0, uses.length);
     }
-    public Instruction(int opcode, Operand.RegisterOperand def, Operand... uses) {
+    protected Instruction(int opcode, Operand.RegisterOperand def, Operand... uses) {
         this.opcode = opcode;
         this.def = def;
         this.uses = new Operand[uses.length];
@@ -373,6 +373,7 @@ public Register inputAsRegister(int i) {
         public Operand input(int i) {
             return uses[i];
         }
+        public int numInputs() { return uses.length; }
         public boolean isRegisterInput(int i) {
             return uses[i] instanceof Operand.RegisterOperand;
         }

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

@@ -183,7 +183,7 @@ private void removeEdge(BasicBlock source, BasicBlock target) {
         Instruction instruction = source.instructions.get(idx);
         if (instruction instanceof Instruction.ConditionalBranch cbr) {
             BasicBlock remainingExecutableBlock = (cbr.falseBlock == target) ? cbr.trueBlock : cbr.falseBlock;
-            source.instructions.set(idx, new Instruction.Jump(remainingExecutableBlock));
+            source.update(idx, new Instruction.Jump(remainingExecutableBlock));
         }
         // Remove phis in target corresponding to the input
         for (var phi: target.phis()) {
@@ -318,6 +318,7 @@ public String toString() {
      */
     private boolean evalInstruction(Instruction instruction) {
         BasicBlock block = instruction.block;
+        assert block != null;
         boolean changed = false;
         switch (instruction) {
             case Instruction.Ret retInst -> {
@@ -448,8 +449,13 @@ private boolean visitPhi(BasicBlock block, Instruction.Phi phiInst) {
             BasicBlock pred = block.predecessors.get(j);
             // We ignore non-executable edges
             if (isEdgeExecutable(pred, block)) {
-                LatticeElement varValue = valueLattice.get(phiInst.inputAsRegister(j));
-                newValue.meet(varValue);
+                if (phiInst.isRegisterInput(j)) {
+                    LatticeElement varValue = valueLattice.get(phiInst.inputAsRegister(j));
+                    newValue.meet(varValue);
+                }
+                else if (phiInst.input(j) instanceof Operand.ConstantOperand constantOperand) {
+                    newValue.meet(constantOperand.value);
+                }
             }
         }
         return oldValue.meet(newValue);