Allow `LocalVariable` to be assigned more than once (#2288)

* Allow `LocalVariable` to be assigned more than once

This allows us to write flow controls like loops and if-elses with
LocalVariables participating in phi nodes.

* Add `GetLocalNumber` to operand

2 files changed, 11 insertions, 10 deletions

diff --git a/ARMeilleure/CodeGen/RegisterAllocators/HybridAllocator.cs b/ARMeilleure/CodeGen/RegisterAllocators/HybridAllocator.cs
index aa10aea0..2f68c43f 100644
--- a/ARMeilleure/CodeGen/RegisterAllocators/HybridAllocator.cs
+++ b/ARMeilleure/CodeGen/RegisterAllocators/HybridAllocator.cs
@@ -83,9 +83,10 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
             int intFreeRegisters = regMasks.IntAvailableRegisters;
             int vecFreeRegisters = regMasks.VecAvailableRegisters;
 
-            BlockInfo[] blockInfo = new BlockInfo[cfg.Blocks.Count];
+            var blockInfo = new BlockInfo[cfg.Blocks.Count];
 
-            List<LocalInfo> locInfo = new List<LocalInfo>();
+            var locInfo = new List<LocalInfo>();
+            var locVisited = new HashSet<Operand>();
 
             for (int index = cfg.PostOrderBlocks.Length - 1; index >= 0; index--)
             {
@@ -109,7 +110,7 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
 
                         if (source.Kind == OperandKind.LocalVariable)
                         {
-                            locInfo[source.AsInt32() - 1].SetBlockIndex(block.Index);
+                            locInfo[source.GetLocalNumber() - 1].SetBlockIndex(block.Index);
                         }
                         else if (source.Kind == OperandKind.Memory)
                         {
@@ -117,12 +118,12 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
 
                             if (memOp.BaseAddress != null)
                             {
-                                locInfo[memOp.BaseAddress.AsInt32() - 1].SetBlockIndex(block.Index);
+                                locInfo[memOp.BaseAddress.GetLocalNumber() - 1].SetBlockIndex(block.Index);
                             }
 
                             if (memOp.Index != null)
                             {
-                                locInfo[memOp.Index.AsInt32() - 1].SetBlockIndex(block.Index);
+                                locInfo[memOp.Index.GetLocalNumber() - 1].SetBlockIndex(block.Index);
                             }
                         }
                     }
@@ -135,9 +136,9 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
                         {
                             LocalInfo info;
 
-                            if (dest.Value != 0)
+                            if (!locVisited.Add(dest))
                             {
-                                info = locInfo[dest.AsInt32() - 1];
+                                info = locInfo[dest.GetLocalNumber() - 1];
                             }
                             else
                             {
@@ -198,7 +199,7 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
 
                     void AllocateRegister(Operand source, MemoryOperand memOp, int srcIndex)
                     {
-                        LocalInfo info = locInfo[source.AsInt32() - 1];
+                        LocalInfo info = locInfo[source.GetLocalNumber() - 1];
 
                         info.UseCount++;
 
@@ -317,7 +318,7 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
                             continue;
                         }
 
-                        LocalInfo info = locInfo[dest.AsInt32() - 1];
+                        LocalInfo info = locInfo[dest.GetLocalNumber() - 1];
 
                         if (info.UseCount == 0 && !info.PreAllocated)
                         {
diff --git a/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs b/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs
index cd36bdc0..88adeeb0 100644
--- a/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs
+++ b/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs
@@ -976,7 +976,7 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
         {
             if (operand.Kind == OperandKind.LocalVariable)
             {
-                return operand.AsInt32();
+                return operand.GetLocalNumber();
             }
             else if (operand.Kind == OperandKind.Register)
             {