fix fallback codegen on bool #3451

Job	Run time
macOS / release / homebrew-clang	5m 48s
Windows / release / msvc	29m 58s
macOS / debug / homebrew-clang	5m 9s
Windows / release / clang-cl	22m 29s
macOS / release / system-clang	3m 53s
macOS / debug / system-clang	4m 7s
Windows / release / llvm	23m 58s
Windows / debug / msvc	15m 0s
Windows / debug / clang-cl	14m 40s
Windows / debug / llvm	28m 9s
	2h 33m 11s

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