[llvm-dev] Signed or unsigned EQ/NEQ

James Courtier-Dutton via llvm-dev llvm-dev at lists.llvm.org
Sat Nov 18 05:28:04 PST 2017


I am writing a decompiler. For this, i need to do type inference
propagation. EQ/NEQ do not provide any indication of type. So the only
solution is to infer it from other uses of the same registers.
I think you will have to do the same.
Also, there are problem edge cases. What if one register is signed and the
other is unsigned?

Kind regards


On 17 Nov 2017 21:12, "Dounia Khaldi via llvm-dev" <llvm-dev at lists.llvm.org>

> Hello,
> In one of the loop transformations I am  developing, I need to convert eq
> and neq loop latch condition into less than or greater than depending on
> the control flow.
> The problem is that  CmpInst::ICMP_EQ and CmpInst::ICMP_NE are neither
> signed nor unsigned in LLVM. Also, I did not find a way to find out if the
> integer operands of the CmpInst are signed or unsigned. Apparently, LLVM
> does not distinguish in its type system between signed and unsigned
> variables. So, I am not able to generate the appropriate signed or unsigned
> Do you have a solution for this?
> Thanks,
> Dounia
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