[LLVMdev] Why are imm shifts where imm >= width type eliminated entirely?

[Ryan Taylor]

For example:

unsigned int x, y;

void foo()
{
     y = x >> 129;
}

Where int is a 16bit type, the .ll is producing only 'ret void' at O3. At
O0 the .ll looks fine but then llc gets rid of it an simply returns.

I'm just curious what the reasoning is for this? It isn't trying to set y
to anything at all.

Thanks.
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