JIT: Ensure entry block has no predecessors on RegisterUsage pass (#6951)
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2 changed files with 22 additions and 2 deletions
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@ -11,7 +11,7 @@ namespace ARMeilleure.Translation
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private int[] _postOrderMap;
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public int LocalsCount { get; private set; }
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public BasicBlock Entry { get; }
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public BasicBlock Entry { get; private set; }
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public IntrusiveList<BasicBlock> Blocks { get; }
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public BasicBlock[] PostOrderBlocks => _postOrderBlocks;
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public int[] PostOrderMap => _postOrderMap;
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@ -34,6 +34,15 @@ namespace ARMeilleure.Translation
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return result;
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}
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public void UpdateEntry(BasicBlock newEntry)
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{
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newEntry.AddSuccessor(Entry);
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Entry = newEntry;
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Blocks.AddFirst(newEntry);
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Update();
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}
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public void Update()
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{
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RemoveUnreachableBlocks(Blocks);
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@ -89,6 +89,17 @@ namespace ARMeilleure.Translation
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public static void RunPass(ControlFlowGraph cfg, ExecutionMode mode)
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{
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if (cfg.Entry.Predecessors.Count != 0)
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{
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// We expect the entry block to have no predecessors.
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// This is required because we have a implicit context load at the start of the function,
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// but if there is a jump to the start of the function, the context load would trash the modified values.
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// Here we insert a new entry block that will jump to the existing entry block.
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BasicBlock newEntry = new BasicBlock(cfg.Blocks.Count);
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cfg.UpdateEntry(newEntry);
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}
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// Compute local register inputs and outputs used inside blocks.
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RegisterMask[] localInputs = new RegisterMask[cfg.Blocks.Count];
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RegisterMask[] localOutputs = new RegisterMask[cfg.Blocks.Count];
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@ -201,7 +212,7 @@ namespace ARMeilleure.Translation
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// The only block without any predecessor should be the entry block.
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// It always needs a context load as it is the first block to run.
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if (block.Predecessors.Count == 0 || hasContextLoad)
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if (block == cfg.Entry || hasContextLoad)
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{
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long vecMask = globalInputs[block.Index].VecMask;
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long intMask = globalInputs[block.Index].IntMask;
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