Class: Optimize::Passes::ConstFoldTier2Pass

Inherits:
Optimize::Pass show all
Defined in:
lib/optimize/passes/const_fold_tier2_pass.rb

Overview

Tier 2 const-fold: frozen top-level constants.

Scans the whole IR tree for ‘setconstant :NAME` sites. Admits a name to the fold table only when its sole assignment is a top-level literal:

<literal-producer>
putspecialobject 3
setconstant :NAME

Any other assignment shape (nested ‘dup`-flavored, non-literal RHS, reassignment) taints the name — both removing it from the fold table and barring re-admission.

Fold phase rewrites ‘opt_getconstant_path <idx>` where `object_table` is a single-element T_ARRAY whose symbol is in the fold table.

Constant Summary collapse

TABLE_KEY = 
:const_fold_tier2_table
TAINTED_KEY = 
:const_fold_tier2_tainted
SCANNED_KEY = 
:const_fold_tier2_scanned

Instance Method Summary collapse

Methods inherited from Optimize::Pass

#one_shot?

Instance Method Details

#apply(function, type_env:, log:, object_table: nil, **_extras) ⇒ Object 



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# File 'lib/optimize/passes/const_fold_tier2_pass.rb', line 33

def apply(function, type_env:, log:, object_table: nil, **_extras)
  _ = type_env
  return unless object_table

  root = tree_root(function)
  root.misc ||= {}
  unless root.misc[SCANNED_KEY]
    root.misc[SCANNED_KEY]  = true
    root.misc[TABLE_KEY]    = {}
    root.misc[TAINTED_KEY]  = Set.new
    scan_tree(root, object_table, log, root.misc[TABLE_KEY], root.misc[TAINTED_KEY])
  end

  table = root.misc[TABLE_KEY]
  return if table.empty?

  insts = function.instructions
  return unless insts

  i = 0
  while i < insts.size
    inst = insts[i]
    if inst.opcode == :opt_getconstant_path
      name = single_name_for_path(inst, object_table)
      if name && table.key?(name)
        replacement = emit_literal(table[name], line: inst.line, object_table: object_table)
        if replacement
          function.splice_instructions!(i..i, [replacement])
          log.rewrite(pass: name_sym, reason: :folded,
                      file: function.path, line: (inst.line || function.first_lineno || 0))
        end
      end
    end
    i += 1
  end
end

#name ⇒ Object 



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# File 'lib/optimize/passes/const_fold_tier2_pass.rb', line 31

def name = :const_fold_tier2