Start peephole #255

Job	Run time
abi-dump-setup	1m 25s
Build lldb / Lit Tests (ubuntu-latest)	1h 44m 19s
Build lldb / Lit Tests (windows-2019)	2m 3s
Build lldb / Lit Tests (macOS-latest)	1h 10m 22s
Test lld / Lit Tests (ubuntu-latest)	56m 14s
Test llvm,clang,libclc / Lit Tests (ubuntu-latest)	2h 35m 15s
Test lld / Lit Tests (windows-2019)	1m 56s
Test llvm,clang,libclc / Lit Tests (windows-2019)	1m 53s
Test lld / Lit Tests (macOS-latest)	46m 9s
Test llvm,clang,libclc / Lit Tests (macOS-latest)	2h 17m 6s
abi-dump (build-baseline)	32m 0s
abi-dump (build-latest)	32m 26s
abi-compare	29s
	10h 41m 37s

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