https://github.com/vitalybuka created https://github.com/llvm/llvm-project/pull/72707
Caller puts argument shadow one by one into __msan_va_arg_tls, until it reaches kParamTLSSize. After that it still increment OverflowOffset but does not store the shadow. Callee needs OverflowOffset to prepare a shadow for the entire overflow area. It's done by creating "varargs shadow copy" for complete list of args, copying available shadow from __msan_va_arg_tls, and clearing the rest. However callee does not know if the tail of __msan_va_arg_tls was not able to fit an argument, and callee will copy tail shadow into "varargs shadow copy", and later used as a shadow for an omitted argument. So that unused tail of the __msan_va_arg_tls must be cleared if left unused. This allows us to enable compiler-rt/test/msan/vararg_shadow.cpp for x86. _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
