[llvm-dev] new @llvm.memcpy and @llvm.memset API in trunk - how to use alignment?

[Friedman, Eli via llvm-dev]

On 3/22/2018 3:15 PM, Andrew Kelley via llvm-dev wrote:
> The new @llvm.memcpy API does not have an alignment parameter. Instead 
> the docs say to use the align <n> attribute. How is this supposed to 
> work with different alignments?
>
> For example, I have one memcpy with align 4, align 4, and another with 
> align 1, align 1.
>
> ; Function Attrs: argmemonly nounwind
> declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly align 
> 4, i8* nocapture readonly align 4, i64, i1) #3
>
> ; Function Attrs: argmemonly nounwind
> declare void @llvm.memcpy.p0i8.p0i8.i64.1(i8* nocapture writeonly 
> align 1, i8* nocapture readonly align 1, i64, i1) #3
>
>
> When I add these multiple definitions to the module, llvm mangles the 
> name, adding `.1` to the second one, and I get "Intrinsic name not 
> mangled correctly for type arguments!"
>
> What's the correct way to do this?

You're not supposed to add the alignment to the function declaration; 
just add it to the call itself.  (If you're using IRBuilder, 
CreateMemCpy will take care of this for you.)

-Eli

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