2421186d97
* Generalize tail continues * Fix DecodeBasicBlock `Next` and `Branch` would be null, which is not the state expected by the branch instructions. They end up branching or falling into a block which is never populated by the `Translator`. This causes an assert to be fired when building the CFG. * Clean up Decode overloads * Do not synchronize when branching into exit block If we're branching into an exit block, that exit block will tail continue into another translation which already has a synchronization. * Remove A32 predicate tail continue If `block` is not an exit block then the `block.Next` must exist (as per the last instruction of `block`). * Throw if decoded 0 blocks Address gdkchan's feedback * Rebuild block list instead of setting to null Address gdkchan's feedback
90 lines
2.9 KiB
C#
90 lines
2.9 KiB
C#
using System;
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using System.Collections.Generic;
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namespace ARMeilleure.Decoders.Optimizations
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{
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static class TailCallRemover
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{
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public static Block[] RunPass(ulong entryAddress, List<Block> blocks)
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{
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// Detect tail calls:
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// - Assume this function spans the space covered by contiguous code blocks surrounding the entry address.
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// - A jump to an area outside this contiguous region will be treated as an exit block.
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// - Include a small allowance for jumps outside the contiguous range.
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if (!Decoder.BinarySearch(blocks, entryAddress, out int entryBlockId))
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{
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throw new InvalidOperationException("Function entry point is not contained in a block.");
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}
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const ulong allowance = 4;
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Block entryBlock = blocks[entryBlockId];
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Block startBlock = entryBlock;
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Block endBlock = entryBlock;
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int startBlockIndex = entryBlockId;
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int endBlockIndex = entryBlockId;
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for (int i = entryBlockId + 1; i < blocks.Count; i++) // Search forwards.
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{
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Block block = blocks[i];
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if (endBlock.EndAddress < block.Address - allowance)
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{
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break; // End of contiguous function.
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}
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endBlock = block;
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endBlockIndex = i;
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}
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for (int i = entryBlockId - 1; i >= 0; i--) // Search backwards.
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{
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Block block = blocks[i];
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if (startBlock.Address > block.EndAddress + allowance)
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{
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break; // End of contiguous function.
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}
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startBlock = block;
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startBlockIndex = i;
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}
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if (startBlockIndex == 0 && endBlockIndex == blocks.Count - 1)
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{
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return blocks.ToArray(); // Nothing to do here.
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}
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// Mark branches outside of contiguous region as exit blocks.
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for (int i = startBlockIndex; i <= endBlockIndex; i++)
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{
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Block block = blocks[i];
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if (block.Branch != null && (block.Branch.Address > endBlock.EndAddress || block.Branch.EndAddress < startBlock.Address))
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{
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block.Branch.Exit = true;
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block.Branch.TailCall = true;
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}
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}
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var newBlocks = new List<Block>(blocks.Count);
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// Finally, rebuild decoded block list, ignoring blocks outside the contiguous range.
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for (int i = 0; i < blocks.Count; i++)
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{
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Block block = blocks[i];
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if (block.Exit || (i >= startBlockIndex && i <= endBlockIndex))
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{
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newBlocks.Add(block);
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}
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}
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return newBlocks.ToArray();
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}
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}
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}
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