832666c45e
* Manually rename BasicBlock to BlockPredecessor BasicBlock is a pair of (Ebb, Inst) that is used to represent the basic block subcomponent of an Ebb that is a predecessor to an Ebb. Eventually we will be able to remove this struct, but for now it makes sense to give it a non-conflicting name so that we can start to transition Ebb to represent a basic block. I have not updated any comments that refer to BasicBlock, as eventually we will remove BlockPredecessor and replace with Block, which is a basic block, so the comments will become correct. * Manually rename SSABuilder block types to avoid conflict SSABuilder has its own Block and BlockData types. These along with associated identifier will cause conflicts in a later commit, so they are renamed to be more verbose here. * Automatically rename 'Ebb' to 'Block' in *.rs * Automatically rename 'EBB' to 'block' in *.rs * Automatically rename 'ebb' to 'block' in *.rs * Automatically rename 'extended basic block' to 'basic block' in *.rs * Automatically rename 'an basic block' to 'a basic block' in *.rs * Manually update comment for `Block` `Block`'s wikipedia article required an update. * Automatically rename 'an `Block`' to 'a `Block`' in *.rs * Automatically rename 'extended_basic_block' to 'basic_block' in *.rs * Automatically rename 'ebb' to 'block' in *.clif * Manually rename clif constant that contains 'ebb' as substring to avoid conflict * Automatically rename filecheck uses of 'EBB' to 'BB' 'regex: EBB' -> 'regex: BB' '$EBB' -> '$BB' * Automatically rename 'EBB' 'Ebb' to 'block' in *.clif * Automatically rename 'an block' to 'a block' in *.clif * Fix broken testcase when function name length increases Test function names are limited to 16 characters. This causes the new longer name to be truncated and fail a filecheck test. An outdated comment was also fixed.
47 lines
1.5 KiB
Rust
47 lines
1.5 KiB
Rust
//! Unreachable code elimination.
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use crate::cursor::{Cursor, FuncCursor};
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use crate::dominator_tree::DominatorTree;
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use crate::flowgraph::ControlFlowGraph;
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use crate::ir;
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use crate::timing;
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use log::debug;
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/// Eliminate unreachable code.
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///
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/// This pass deletes whole blocks that can't be reached from the entry block. It does not delete
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/// individual instructions whose results are unused.
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///
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/// The reachability analysis is performed by the dominator tree analysis.
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pub fn eliminate_unreachable_code(
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func: &mut ir::Function,
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cfg: &mut ControlFlowGraph,
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domtree: &DominatorTree,
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) {
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let _tt = timing::unreachable_code();
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let mut pos = FuncCursor::new(func);
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while let Some(block) = pos.next_block() {
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if domtree.is_reachable(block) {
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continue;
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}
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debug!("Eliminating unreachable {}", block);
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// Move the cursor out of the way and make sure the next lop iteration goes to the right
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// block.
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pos.prev_block();
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// Remove all instructions from `block`.
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while let Some(inst) = pos.func.layout.first_inst(block) {
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debug!(" - {}", pos.func.dfg.display_inst(inst, None));
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pos.func.layout.remove_inst(inst);
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}
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// Once the block is completely empty, we can update the CFG which removes it from any
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// predecessor lists.
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cfg.recompute_block(pos.func, block);
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// Finally, remove the block from the layout.
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pos.func.layout.remove_block(block);
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}
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}
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