In GetVectorElementPointer - EltSize assertions fail if getSizeInBits is less than 8

[llvmbot]

Bugzilla Link	29018
Version	3.8
OS	Windows NT
Reporter	LLVM Bugzilla Contributor
CC	@RKSimon

Extended Description

The code at lib/CodeGen/SelectionDAG/LegalizeTypes.cpp:1031 seems to have issues if the element size is less than a full byte (e.g., processing a "i1"), as EltSize will truncate to 0 and then the assertion will fail. Allowing the assertion to be ignored if EltSize == 0 seems to fix this issue, but it looks like something that needs more review:

// Calculate the element offset and add it to the pointer.
unsigned EltSize = EltVT.getSizeInBits() / 8; // FIXME: should be ABI size.
if (EltSize)
{
assert(EltSize * 8 == EltVT.getSizeInBits() &&
"Converting bits to bytes lost precision");
}

[Endilll]

I don't see 8-bit bytes being hardcoded in that file as of post-16 trunk.

CC @efriedma-quic @rjmccall

[efriedma-quic]

I'm pretty sure the code in question was fixed.

[vfdff]

hi @efriedma-quic ,I find there is some crash related above assert, eg: 42304, 54423

[efriedma-quic]

This isn't really a useful ticket as-is; please track each issue in a separate ticket, e.g. "SplitVecRes_INSERT_SUBVECTOR is broken for non-byte-size types", or "SplitVecOp_EXTRACT_VECTOR_ELT is broken for non-byte-size types larger than 8 bits".