This eagerly reports use of undef values when passed to noundef
parameters or returned from noundef functions.
This also decreases binary sizes under msan.
To go back to the previous behavior, pass `-fno-sanitize-memory-param-retval`.
Reviewed By: vitalybuka, MaskRay
Differential Revision: https://reviews.llvm.org/D134669
Let -fsanitize-memory-param-retval be used together with
-fsanitize=kernel-memory, so that it can be applied when building the
Linux kernel.
Also add clang/test/CodeGen/kmsan-param-retval.c to ensure that
-fsanitize-memory-param-retval eliminates shadow accesses for parameters
marked as undef.
Reviewed By: eugenis, vitalybuka
Differential Revision: https://reviews.llvm.org/D127860
Arthur Eubanks