[llvm-dev] LLVM v3.9.0 and math built-ins

[Friedman, Eli via llvm-dev]

On 9/20/2016 4:12 AM, Martin J. O'Riordan via llvm-dev wrote:
>
> I modified my sources to force ‘readnone’ and even tried 
> ‘setDoesNotAccessMemory()’ on the math functions, but this still 
> results in one call occurring and the code generated is effectively:
>
> (void)exp(1.0);
>
> return 0;
>
>   %1 = tail call float @exp(float 1.000000e+00)
>
> ; Function Attrs: readnone
>
> declare float @exp(float) local_unnamed_addr #1
>

You have to set readonly on the call, not the function ("tail call float 
@exp(float 1.000000e+00) readonly") ; the attributes on a function 
declaration are generally ignored by LLVM.


For the difference between 3.8 and 3.9, see 
https://llvm.org/bugs/show_bug.cgi?id=30464 .

-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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