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using ARMeilleure.IntermediateRepresentation;
using ARMeilleure.Translation;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
namespace ARMeilleure.CodeGen.Optimizations
{
static class Optimizer
{
public static void RunPass(ControlFlowGraph cfg)
{
bool modified;
do
{
modified = false;
foreach (BasicBlock block in cfg.Blocks)
{
LinkedListNode<Node> node = block.Operations.First;
while (node != null)
{
LinkedListNode<Node> nextNode = node.Next;
bool isUnused = IsUnused(node.Value);
if (!(node.Value is Operation operation) || isUnused)
{
if (isUnused)
{
RemoveNode(block, node);
modified = true;
}
node = nextNode;
continue;
}
ConstantFolding.RunPass(operation);
Simplification.RunPass(operation);
if (DestIsLocalVar(operation) && IsPropagableCopy(operation))
{
PropagateCopy(operation);
RemoveNode(block, node);
modified = true;
}
node = nextNode;
}
}
}
while (modified);
}
private static void PropagateCopy(Operation copyOp)
{
// Propagate copy source operand to all uses of the destination operand.
Operand dest = copyOp.Destination;
Operand source = copyOp.GetSource(0);
Node[] uses = dest.Uses.ToArray();
foreach (Node use in uses)
{
for (int index = 0; index < use.SourcesCount; index++)
{
if (use.GetSource(index) == dest)
{
use.SetSource(index, source);
}
}
}
}
private static void RemoveNode(BasicBlock block, LinkedListNode<Node> llNode)
{
// Remove a node from the nodes list, and also remove itself
// from all the use lists on the operands that this node uses.
block.Operations.Remove(llNode);
Node node = llNode.Value;
for (int index = 0; index < node.SourcesCount; index++)
{
node.SetSource(index, null);
}
Debug.Assert(node.Destination == null || node.Destination.Uses.Count == 0);
node.Destination = null;
}
private static bool IsUnused(Node node)
{
return DestIsLocalVar(node) && node.Destination.Uses.Count == 0 && !HasSideEffects(node);
}
private static bool DestIsLocalVar(Node node)
{
return node.Destination != null && node.Destination.Kind == OperandKind.LocalVariable;
}
private static bool HasSideEffects(Node node)
{
return (node is Operation operation) && operation.Instruction == Instruction.Call;
}
private static bool IsPropagableCopy(Operation operation)
{
if (operation.Instruction != Instruction.Copy)
{
return false;
}
return operation.Destination.Type == operation.GetSource(0).Type;
}
}
}
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