[cfe-dev] GCC 5.1.0 producing invalid Clang binaries?

[Alexander Potapenko via cfe-dev]

Hi,

Trying to build a (somewhat) fresh Clang to run on a rather old
machine, I've attempted to use GCC 5.1.0 compiled according to the
instructions at
https://llvm.org/docs/GettingStarted.html#getting-a-modern-host-c-toolchain=
.
It turned out that the resulting Clang binaries crash on a trivial
assembly file (reduced from the Linux kernel source):

$ cat trampoline_64.s
.code32
$ clang -m16   -c -o trampoline_64.o trampoline_64.s -w
clang-10: /home/glider/llvm-project/llvm/lib/Target/X86/AsmParser/X86AsmPar=
ser.cpp:985:
void {anonymous}::X86AsmParser::SwitchMode(unsigned int): Assertion
`FeatureBitset({mode}) =3D=3D (STI.getFeatureBits() & AllModes)' failed.
...

The same Clang version (c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
works perfectly fine when compiled with a newer GCC 8.3.0.
Could it be so that GCC 5.1.0 miscompiles Clang and thus shouldn't be
used as the minimum build requirement?



-- 
Alexander Potapenko
Software Engineer

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