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 An outdated comment was also fixed.
74 lines
3.0 KiB
Rust
74 lines
3.0 KiB
Rust
//! Instruction shrinking.
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//!
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//! Sometimes there are multiple valid encodings for a given instruction. Cranelift often initially
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//! chooses the largest one, because this typically provides the register allocator the most
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//! flexibility. However, once register allocation is done, this is no longer important, and we
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//! can switch to smaller encodings when possible.
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use crate::ir::instructions::InstructionData;
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use crate::ir::Function;
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use crate::isa::TargetIsa;
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use crate::regalloc::RegDiversions;
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use crate::timing;
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use log::debug;
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/// Pick the smallest valid encodings for instructions.
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pub fn shrink_instructions(func: &mut Function, isa: &dyn TargetIsa) {
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let _tt = timing::shrink_instructions();
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let encinfo = isa.encoding_info();
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let mut divert = RegDiversions::new();
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for block in func.layout.blocks() {
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// Load diversions from predecessors.
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divert.at_block(&func.entry_diversions, block);
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for inst in func.layout.block_insts(block) {
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let enc = func.encodings[inst];
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if enc.is_legal() {
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// regmove/regfill/regspill are special instructions with register immediates
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// that represented as normal operands, so the normal predicates below don't
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// handle them correctly.
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//
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// Also, they need to be presented to the `RegDiversions` to update the
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// location tracking.
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//
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// TODO: Eventually, we want the register allocator to avoid leaving these special
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// instructions behind, but for now, just temporarily avoid trying to shrink them.
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let inst_data = &func.dfg[inst];
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match inst_data {
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InstructionData::RegMove { .. }
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| InstructionData::RegFill { .. }
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| InstructionData::RegSpill { .. } => {
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divert.apply(inst_data);
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continue;
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}
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_ => (),
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}
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let ctrl_type = func.dfg.ctrl_typevar(inst);
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// Pick the last encoding with constraints that are satisfied.
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let best_enc = isa
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.legal_encodings(func, &func.dfg[inst], ctrl_type)
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.filter(|e| encinfo.constraints[e.recipe()].satisfied(inst, &divert, &func))
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.min_by_key(|e| encinfo.byte_size(*e, inst, &divert, &func))
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.unwrap();
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if best_enc != enc {
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func.encodings[inst] = best_enc;
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debug!(
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"Shrunk [{}] to [{}] in {}, reducing the size from {} to {}",
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encinfo.display(enc),
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encinfo.display(best_enc),
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func.dfg.display_inst(inst, isa),
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encinfo.byte_size(enc, inst, &divert, &func),
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encinfo.byte_size(best_enc, inst, &divert, &func)
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);
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}
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}
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}
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}
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}
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