From the same build, also related to branch folding:

FAILED: obj/third_party/expat/expat/xmlparse.obj 
../../third_party/llvm-build/Release+Asserts/bin/clang-cl.exe /nologo /showIncludes  -imsvc..\..\third_party\depot_tools\win_toolchain\vs_files\3bc0ec615cf20ee342f3bc29bc991b5ad66d8d2c\win_sdk\Include\10.0.17134.0\um -imsvc..\..\third_party\depot_tools\win_toolchain\vs_files\3bc0ec615cf20ee342f3bc29bc991b5ad66d8d2c\win_sdk\Include\10.0.17134.0\shared -imsvc..\..\third_party\depot_tools\win_toolchain\vs_files\3bc0ec615cf20ee342f3bc29bc991b5ad66d8d2c\win_sdk\Include\10.0.17134.0\winrt -imsvc..\..\third_party\depot_tools\win_toolchain\vs_files\3bc0ec615cf20ee342f3bc29bc991b5ad66d8d2c\win_sdk\Include\10.0.17134.0\ucrt -imsvc..\..\third_party\depot_tools\win_toolchain\vs_files\3bc0ec615cf20ee342f3bc29bc991b5ad66d8d2c\VC\Tools\MSVC\14.14.26428\include -imsvc..\..\third_party\depot_tools\win_toolchain\vs_files\3bc0ec615cf20ee342f3bc29bc991b5ad66d8d2c\VC\Tools\MSVC\14.14.26428\atlmfc\include -D_LIB -DCOMPILED_FROM_DSP -DV8_DEPRECATION_WARNINGS -DUSE_AURA=1 -DNO_TCMALLOC -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DCHROMIUM_BUILD -DFIELDTRIAL_TESTING_ENABLED "-DCR_CLANG_REVISION=\"345019\"" -D_HAS_NODISCARD -D_HAS_EXCEPTIONS=0 -DCOMPONENT_BUILD -D__STD_C -D_CRT_RAND_S -D_CRT_SECURE_NO_DEPRECATE -D_SCL_SECURE_NO_DEPRECATE -D_ATL_NO_OPENGL -D_WINDOWS -DCERT_CHAIN_PARA_HAS_EXTRA_FIELDS -DPSAPI_VERSION=1 -DWIN32 -D_SECURE_ATL -D_USING_V110_SDK71_ -DWINAPI_FAMILY=WINAPI_FAMILY_DESKTOP_APP -DWIN32_LEAN_AND_MEAN -DNOMINMAX -D_UNICODE -DUNICODE -DNTDDI_VERSION=0x0A000002 -D_WIN32_WINNT=0x0A00 -DWINVER=0x0A00 -D_DEBUG -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DWTF_USE_DYNAMIC_ANNOTATIONS=1 -DXML_STATIC -I../.. -Igen -I../../third_party/expat/files/lib /utf-8 /X -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -fcolor-diagnostics -fmerge-all-constants -Xclang -mllvm -Xclang -instcombine-lower-dbg-declare=0 -no-canonical-prefixes -fcomplete-member-pointers /Gy /FS /bigobj /d2FastFail /Zc:sizedDealloc- -fmsc-version=1911 -m32 /Brepro /W4 -Wimplicit-fallthrough -Wthread-safety /WX /wd4091 /wd4127 /wd4251 /wd4275 /wd4312 /wd4324 /wd4351 /wd4355 /wd4503 /wd4589 /wd4611 /wd4100 /wd4121 /wd4244 /wd4505 /wd4510 /wd4512 /wd4610 /wd4838 /wd4995 /wd4996 /wd4456 /wd4457 /wd4458 /wd4459 /wd4200 /wd4201 /wd4204 /wd4221 /wd4245 /wd4267 /wd4305 /wd4389 /wd4702 /wd4701 /wd4703 /wd4661 /wd4706 /wd4715 /wd4267 -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-unneeded-internal-declaration -Wno-undefined-var-template -Wno-null-pointer-arithmetic -Wno-nonportable-include-path -Wno-ignored-pragma-optimize -Wno-defaulted-function-deleted /Z7 -fno-standalone-debug /MDd -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare /O2 /Ob2 /Oy- /Zc:inline /Gw /TC /c ../../third_party/expat/files/lib/xmlparse.c /Foobj/third_party/expat/expat/xmlparse.obj /Fd"obj/third_party/expat/expat_c.pdb"
Assertion failed: MBBICommon != MBBIECommon && "Reached BB end within common tail length!", file C:\b\c\b\ToTWin_dbg_\src\third_party\llvm\lib\CodeGen\BranchFolding.cpp, line 863
LLVMSymbolizer: error reading file: 'C:\b\c\b\ToTWin_dbg_\src\third_party\llvm-build\Release+Asserts\bin\clang.pdb': An unknown error has occurred. HRESULT: 0x8007007E: Calling NoRegCoCreate
LLVMSymbolizer: error reading file: 'kernel32.pdb': An unknown error has occurred. HRESULT: 0x8007007E: Calling NoRegCoCreate
LLVMSymbolizer: error reading file: 'ntdll.pdb': An unknown error has occurred. HRESULT: 0x8007007E: Calling NoRegCoCreate

And here's one from an ios bot:
https://ci.chromium.org/buildbot/chromium.clang/ToTiOSDevice/10096

FAILED: clang_x64/obj/third_party/boringssl/boringssl/cbb.o 
../../third_party/llvm-build/Release+Asserts/bin/clang -MMD -MF clang_x64/obj/third_party/boringssl/boringssl/cbb.o.d -DV8_DEPRECATION_WARNINGS -DNO_TCMALLOC -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DCHROMIUM_BUILD -DFIELDTRIAL_TESTING_ENABLED -D_LIBCPP_HAS_NO_ALIGNED_ALLOCATION -DCR_XCODE_VERSION=1000 -DCR_CLANG_REVISION=\"345017\" -D__ASSERT_MACROS_DEFINE_VERSIONS_WITHOUT_UNDERSCORE=0 -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DBORINGSSL_ALLOW_CXX_RUNTIME -DBORINGSSL_IMPLEMENTATION -DBORINGSSL_NO_STATIC_INITIALIZER -DOPENSSL_SMALL -D_XOPEN_SOURCE=700 -I../.. -Iclang_x64/gen -I../../third_party/boringssl/src/include -fno-strict-aliasing -fstack-protector -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -fcolor-diagnostics -fmerge-all-constants -Xclang -mllvm -Xclang -instcombine-lower-dbg-declare=0 -no-canonical-prefixes -arch x86_64 -O2 -fno-omit-frame-pointer -gdwarf-2 -isysroot ../../../../../xcode_ios_10a254a.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk -mmacosx-version-min=10.9.0 -fvisibility=hidden -Xclang -load -Xclang ../../third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.dylib -Xclang -add-plugin -Xclang find-bad-constructs -Xclang -plugin-arg-find-bad-constructs -Xclang enforce-in-thirdparty-webkit -Xclang -plugin-arg-find-bad-constructs -Xclang check-enum-max-value -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Wno-shorten-64-to-32 -Werror -Wall -Wno-unused-variable -Wno-unused-lambda-capture -Wunguarded-availability -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-unneeded-internal-declaration -Wno-undefined-var-template -Wno-null-pointer-arithmetic -Wno-ignored-pragma-optimize -Wno-defaulted-function-deleted -std=c11 -std=c99 -c ../../third_party/boringssl/src/crypto/bytestring/cbb.c -o clang_x64/obj/third_party/boringssl/boringssl/cbb.o
Assertion failed: (MBBICommon != MBBIECommon && "Reached BB end within common tail length!"), function mergeOperations, file /b/c/b/ToTiOSDevice/src/third_party/llvm/lib/CodeGen/BranchFolding.cpp, line 863.

Here's the repro from xmlparse.c

I used Clang r345019

Deleted: xmlparse-d9c3de.sh 9.8 KB

xmlparse-d9c3de.sh 9.8 KB View Download

Deleted: xmlparse-d9c3de.c 5.8 MB

xmlparse-d9c3de.c 5.8 MB View Download

r345021... fails
r345025... fails
r345026... passes

r345026 is the revert for  Issue 898152 , so I guess it was the same root cause.