llvm dev - Jul 2013 - [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

Jeroen,
 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.

Micah
> -----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
> 
> 
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