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Voir sur GitHub[clang] Bitcasts from vectors to integers not supported at compile time
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#159 905 ouverte le 20 sept. 2025
clang:frontendconstexprgood first issue
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Description
I have test case that seems to regressed for latest constexpr changes.
#include<immintrin.h>
constexpr
__m64 foo(__m64 a, int b){
return (__m64)(long long)a << b;
}
int main(){
foo((__m64){5},1);
return 0;
}
gcc-trunk works fine. clang-trunk errors out.
<source>:3:7: error: constexpr function never produces a constant expression [-Winvalid-constexpr]
3 | __m64 foo(__m64 a, int b){
| ^~~
<source>:4:19: note: subexpression not valid in a constant expression
4 | return (__m64)(long long)a << b;
Following change passed
#include<immintrin.h>
constexpr
__m64 foo(__m64 a, int b){
if(b > 63)
return (__m64){0};
return (__m64)(long long)a << b;
}
int main(){
foo((__m64){5},1);
return 0;
}
here is repro https://godbolt.org/z/d7obEcb57 Does anyone know what may be trouble here?