[llvm-dev] What should a truncating store do?

[Jon Chesterfield via llvm-dev]

For example, truncating store of an i32 to i6. My assumption was that this
should write the low six bits of the i32 to somewhere in memory.

Should the top 24 bits of a corresponding 32 bit region of memory be
unchanged, zero,  undefined?

Should the two bits that would round the i6 up to a byte be preserved,
zero, undefined?

I can't write six bits directly so am trying to determine what set of
bitwise ops to apply between a load and subsequent store to emulate the
truncating store.

Thanks!

Jon
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