llvm dev - Apr 2013 - [LLVMdev] Instruction Implementation

Hi and thanks for answering

llc works fine just does not selecting my instruction 

i ve uploaded .ll file

how can i include this attribute "readonly" so i can see if changes
the
generated assembly?


my code is very simple
int main (){
float d, d1 ;
        d= 12.3;
        d1 = d - ceilf(d);

return 0;
}



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Hi,
> i ve uploaded .ll file
Is that the C file that's at the end of your message? To produce a .ll
file, you give clang the "-emit-llvm" option (and probably
"-S").

Anyway, what I see in the C you posted is that Clang is using constant
folding to avoid doing any of the operations you've requested. A
better C file test would be:

float foo(float d) {
  return d - ceilf(d);
}

For me LLVM does use the FCEIL node in that case (it doesn't know what
d is so can't optimise your operations away). I'm still a little
worried that ceilf isn't declared, but LLVM seems to do the
"right"
thing anyway.

I'm also a little worried that your pattern has fadd, but your C
source has a subtraction.
> how can i include this attribute "readonly" so i can see if
changes the
> generated assembly?
The best documentation is probably the "Function Attributes" section
in http://llvm.org/docs/LangRef.html, but it doesn't look like you've
been using LLVM IR so that may not be immediately useful.

Cheers.

Tim.

>I'm also a little worried that your pattern has fadd, but your C 
>source has a subtraction. 
:S i wrote it wrong the true implementation is 
def SUBCEIL_S   : FFR<0x11, 0x3, 16, (outs  FGR32:$fd), (ins  FGR32:$fs),
"frac.s\t$fd, $fs", [(set (f32  FGR32:$fd), (fsub (f32  FGR32:$fs
),(f32
(ceilf FGR32:$fs))))] >; 

I use some C,C++ code to test my backend. 

i use clang with those argument 

-m32 -emit-llvm -S -target mipsel-linux-gnu -I..  
and i have tried to add this in case so it will not use standard libs
-nostdlib -nostdinc -fno-builtin but with no luck

attached the new .ll for code

#include "math.h"
float foo (float x)
{

        return (x - ceilf(x));
}
int main()
{
float d, d1 ;
        d= 12.3f;
        d1= foo(d);
    return 0;
}
 

test.ll <http://llvm.1065342.n5.nabble.com/file/n56383/test.ll>  







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