refactor special registers #3398

Job	Run time
macOS / release / homebrew-clang	4m 52s
Windows / release / msvc	24m 57s
Windows / release / clang-cl	22m 12s
Windows / release / llvm	23m 38s
macOS / debug / homebrew-clang	4m 15s
Windows / debug / msvc	22m 43s
macOS / release / system-clang	3m 47s
Windows / debug / clang-cl	22m 3s
macOS / debug / system-clang	3m 31s
Windows / debug / llvm	22m 38s
	2h 34m 36s

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