[llvm-dev] Issue with getting unsigned Constant from APInt

[Friedman, Eli via llvm-dev]

On 11/19/2018 2:51 PM, Lei Zhang via llvm-dev wrote:
>
> Hi there,
>
> I have been trying to obtain a Constant from an APInt using
> ```
> auto maskConstant = llvm::ConstantInt::get(intTy, maskPiece);
> ```
> where `intTy` is a IntergerType pointer (64-bit) and `maskPiece` is an 
> APInt object. However, if `maskPiece` has the a big value say
> 18374686479671623680, which is 
> 1111111100000000000000000000000000000000000000000000000000000000. The 
> constant will return a negative value -72057594037927936, which looks 
> it is always converted to a signed integer. How can i keep it as unsigned?
>
"i64 18374686479671623680" and "i64 -72057594037927936" are actually the 
same value in LLVM IR.  dump() prints the signed version, but that's 
just for convenience (since "i64 -1" is easier to read).  Integer 
operations have separate signed and unsigned versions where it's 
relevant (e.g. sdiv vs. udiv).

-Eli

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

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