[cfe-dev] [OpenCL] allow __builtin_astype(char4, char3)

[Liu, Yaxun (Sam) via cfe-dev]

Is char3 as_char3(char4 x) a valid OpenCL builtin function?

According to the spec, both have 4 bytes, so it seems to be a valid builtin.

Naturally one would want to implement it as

char3 as_char3(char4 x) { return __builtin_astype(x, char3); }

However this does not work since Clang will generate bitcast <4 x i8> to <3 x i8> and this is an invalid llvm instruction.

Do you think Clang should be patched to generate correct llvm instruction for this case?

Thanks.

Sam
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