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[ARM][AArch64] Revert Android Bionic PT_TLS overaligning hack
This reverts D53906. D53906 increased p_align of PT_TLS on ARM/AArch64 to 32/64 to make the static TLS layout compatible with Android Bionic's ELF TLS. However, this may cause glibc ARM/AArch64 programs to crash (see PR41527). The faulty PT_TLS in the executable satisfies p_vaddr%p_align != 0. The remainder is normally 0 but may be non-zero with the hack in place. The problem is that we increase PT_TLS's p_align after OutputSections' addresses are fixed (assignAddress()). It is possible that p_vaddr%old_p_align = 0 while p_vaddr%new_p_align != 0. For a thread local variable defined in the executable, lld computed TLS offset (local exec) is different from glibc computed TLS offset from another module (initial exec/generic dynamic). Note: PR41527 said the bug affects initial exec but actually generic dynamic is affected as well. (glibc is correct in that it compute offsets that satisfy `offset%p_align == p_vaddr%p_align`, which is a basic ELF requirement. This hack appears to work on FreeBSD rtld, musl<=1.1.22, and Bionic, but that is just because they (and lld) incorrectly compute offsets that satisfy `offset%p_align = 0` instead.) Android developers are fine to revert this patch, carry this patch in their tree before figuring out a long-term solution (e.g. a dummy .tdata with sh_addralign=64 sh_size={0,1} in crtbegin*.o files. The overhead is now insignificant after D62059). Reviewed By: rprichard, srhines Differential Revision: https://reviews.llvm.org/D62055 llvm-svn: 361090
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