[LLVMdev] using f32 in a 64bit integer only architecture

Micah Villmow micah.villmow at smachines.com
Tue Jul 30 08:50:23 PDT 2013

 This most likely is the case that no one has ran into this situation before and there was no need to implement this code path. I ran into this quite often when working on the GPU backend.


> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
> On Behalf Of Jeroen Dobbelaere
> Sent: Tuesday, July 30, 2013 8:27 AM
> To: llvmdev at cs.uiuc.edu
> Subject: [LLVMdev] using f32 in a 64bit integer only architecture
> Hi,
> I am working on a 64bit architecture where only 'i64' is valid (no hardware
> floating point support) and I am triggering a 'Promote may not follow Expand
> or Promote' assertion failure.
> (TargetLowering.h : getTypeConversion)
> When I look into it, I see that the conversion fails because llvm tries to
> convert a 'f32'
> into a 'i32' through a TypeSoftenFloat.
> As i32 needs promotion to i64, this assertion is triggered.
> The other way around: a 32bit architecture (only i32 is valid) with doubles
> (f64) seems to work just fine. So, it seems that a 'TypeSoftenFloat' followed
> by an 'Expand' is valid (f64->i64->i32)
> Note:
> - this is for llvm-3.3
> - In TargetLoweringBase.cpp , I find that (when f32 and f64 are not valid):
> -- the default action for 'f64' is to convert it into a 'i64'
> -- the default action for 'f32' is to convert it into a 'i32'
> Is this kind of support easy to add ? What would be the places that need to
> be updated ?
> (I tried with adding a direct promotion from f32 into i64  in
> TargetLoweringBase.cpp, but that seems to trigger other issues,  so I am not
> sure if that is the right way to go)
> Greetings,
> Jeroen Dobbelaere
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

More information about the llvm-dev mailing list