fatal error LNK1322: cannot avoid potential ARM hazard (Cortex-A53 MPCore processor bug #843419) in section 0x1

[weliveindetail]

We see the following failure since https://ci-external.swift.org/job/swift-main-windows-toolchain-arm64/1023/ (Mar 1):

[23/52][ 44%][95.515s]Linking Swift shared library Sources\SWBCore\SWBCore.dll
FAILED: Sources/SWBCore/SWBCore.dll Sources/SWBCore/SWBCore.lib 
C:\Windows\system32\cmd.exe /C "cd . && T:\1\bin\swiftc.exe -target aarch64-unknown-windows-msvc -j 36 -num-threads 36 -emit-library -sdk "T:/Program Files/Swift/Platforms/Windows.platform/Developer/SDKs/Windows.sdk" -gnone -Xlinker /INCREMENTAL:NO -Xlinker /OPT:REF -Xlinker /OPT:ICF -O -swift-version 5 -libc MD   -Xlinker -implib:Sources\SWBCore\SWBCore.lib   -o Sources\SWBCore\SWBCore.dll @CMakeFiles\SWBCore.rsp && cd ."
<unknown>:0: warning: using (deprecated) legacy driver, Swift installation does not contain swift-driver at: 'C:\Users\swift-ci\jenkins\workspace\swift-main-windows-toolchain-arm64\build\1\bin\swift-driver-new.exe'
   Creating library Sources\SWBCore\SWBCore.lib and object Sources\SWBCore\SWBCore.exp
BuiltinMacros.swift.obj : fatal error LNK1322: cannot avoid potential ARM hazard (Cortex-A53 MPCore processor bug #843419) in section 0x1; please consider using compiler option /Gy if it was not used
clang: error: linker command failed with exit code 1322 (use -v to see invocation)

It may have existed before and hidden by another build issue (Feb 28). Last successful build was Feb 27.

[weliveindetail]

I am not familiar with the details of this breakage, but I assume it's fine to add the recommend compiler option /Gy which enables Function-Level Linking. swift-build is not huge codebase, so link-times shouldn't be critical. And Cortex-A53 doesn't seem like a relevant target for the toolchain.

[compnerd]

Oh, this is interesting! This seems like a LLVM bug. /Gy is not applicable here as that is from the Swift compiler and /Gy is a C/C++ (clang-cl) option.

[compnerd]

FTR, Errata 843419 deals with a adrp in the last 8-bytes of a 4k (page) boundary may not resolve properly. There is a BFD level workaround where the instruction is attempted to be relaxed to a adr if possible or otherwise a veneer is inserted.

[hjyamauchi]

A workaround merged: #79768