[Libclc-dev] Adding fabs to libclc

[Gabriel Rodríguez]

Dear all, 


I have been trying to add support for fabs() to libclc and later to the LLVM-PTX backend. 
This looked simple enough, but I am having trouble starting with the libclc part. I have added 
the following files: 


generic/include/clc/math/fabs.h --------------------------- 

#undef fabs 
#define fabs __clc_fabs 


#define FUNCTION __clc_fabs 
#define INTRINSIC "llvm.fabs" 
#include <clc/math/unary_intrin.inc> 
---------------------------------------------------------- 


generic/include/clc/math/native_fabs.h-------------------- 

#define native_fabs abs 
---------------------------------------------------------- 


And I have added those files to generic/include/clc/clc.h. I expected this to generate 
@llvm.fabs.[f32/f64] functions as happens for sqrt, for instance. However, I find that the 
definition is already different in LLVM IR: 



declare ptx_device double @llvm.fabs.f64(double) 
declare double @llvm.sqrt.f64(double) nounwind readonly 


Since I am unable to get LLVM to lower calls to llvm.fabs as "abs" instructions rather than 
"call.uni", I suspect the declaration differences to be (at least in part) the culprit. Could someone 
point me out in the right direction? 


Thanks in advance, 
Gabriel 

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