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* Replace LinkedList by IntrusiveList to avoid allocations on JIT * Fix wrong replacements
95 lines
3 KiB
C#
95 lines
3 KiB
C#
using ARMeilleure.IntermediateRepresentation;
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using System.Diagnostics;
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namespace ARMeilleure.Translation
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{
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static class Dominance
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{
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// Those methods are an implementation of the algorithms on "A Simple, Fast Dominance Algorithm".
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// https://www.cs.rice.edu/~keith/EMBED/dom.pdf
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public static void FindDominators(ControlFlowGraph cfg)
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{
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BasicBlock Intersect(BasicBlock block1, BasicBlock block2)
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{
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while (block1 != block2)
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{
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while (cfg.PostOrderMap[block1.Index] < cfg.PostOrderMap[block2.Index])
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{
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block1 = block1.ImmediateDominator;
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}
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while (cfg.PostOrderMap[block2.Index] < cfg.PostOrderMap[block1.Index])
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{
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block2 = block2.ImmediateDominator;
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}
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}
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return block1;
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}
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cfg.Entry.ImmediateDominator = cfg.Entry;
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Debug.Assert(cfg.Entry == cfg.PostOrderBlocks[cfg.PostOrderBlocks.Length - 1]);
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bool modified;
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do
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{
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modified = false;
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for (int blkIndex = cfg.PostOrderBlocks.Length - 2; blkIndex >= 0; blkIndex--)
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{
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BasicBlock block = cfg.PostOrderBlocks[blkIndex];
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BasicBlock newIDom = null;
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foreach (BasicBlock predecessor in block.Predecessors)
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{
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if (predecessor.ImmediateDominator != null)
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{
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if (newIDom != null)
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{
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newIDom = Intersect(predecessor, newIDom);
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}
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else
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{
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newIDom = predecessor;
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}
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}
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}
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if (block.ImmediateDominator != newIDom)
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{
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block.ImmediateDominator = newIDom;
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modified = true;
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}
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}
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}
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while (modified);
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}
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public static void FindDominanceFrontiers(ControlFlowGraph cfg)
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{
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for (BasicBlock block = cfg.Blocks.First; block != null; block = block.ListNext)
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{
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if (block.Predecessors.Count < 2)
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{
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continue;
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}
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for (int pBlkIndex = 0; pBlkIndex < block.Predecessors.Count; pBlkIndex++)
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{
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BasicBlock current = block.Predecessors[pBlkIndex];
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while (current != block.ImmediateDominator)
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{
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current.DominanceFrontiers.Add(block);
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current = current.ImmediateDominator;
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}
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}
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}
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}
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}
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} |