[RFC C++ / PR51033 ] Handle __builtin_shuffle in constexpr properly in the C++ frontend.

[Marc Glisse]

On Mon, 18 Jun 2012, Ramana Radhakrishnan wrote:

> This patch following on from the fix for turning on __builtin_shuffle
> for c++ , enables folding of vec_perm_exprs in the front-end for
> constexpr and constructor style values.

Hello,

I took a look, and the example I gave in
http://gcc.gnu.org/ml/gcc-patches/2012-06/msg01066.html
although it doesn't crash the compiler anymore, still fails to compile. I 
am not sure: were you just trying to remove the ICE, or actually support 
this use?

#include <x86intrin.h>
int main(){
   constexpr __m128d x={1.,2.};
   constexpr __m128i y={1,0};
   constexpr __m128d z=__builtin_shuffle(x,y);
}

$ g++ -std=gnu++11 m.cc
m.cc: In function 'int main()':
m.cc:5:23: error: '#'vec_perm_expr' not supported by dump_expr#<expression 
error>' is not a constant expression
    constexpr __m128d z=__builtin_shuffle(x,y);
                        ^

-- 
Marc Glisse