Allow instruction combine (#112) #288

Job	Run time
abi-dump-setup	1m 23s
Test lld / Lit Tests (ubuntu-latest)	56m 4s
Build lldb / Lit Tests (ubuntu-latest)	1h 44m 31s
Test llvm,clang,libclc / Lit Tests (ubuntu-latest)	2h 29m 3s
Test lld / Lit Tests (windows-2019)	2m 27s
Build lldb / Lit Tests (windows-2019)	2m 26s
Test llvm,clang,libclc / Lit Tests (windows-2019)	2m 10s
Test lld / Lit Tests (macOS-latest)	48m 47s
Build lldb / Lit Tests (macOS-latest)	1h 12m 45s
Test llvm,clang,libclc / Lit Tests (macOS-latest)	2h 6m 15s
abi-dump (build-baseline)	32m 33s
abi-dump (build-latest)	32m 0s
abi-compare	27s
	10h 30m 51s

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