Cause:
This diagnostic is emitted by Intel(R) C++ Compiler 14.0 and below. This diagnostic message is emitted when the function modifies the ebx/rbx register. Vectorization requires aligned stack frame: 16 bytes for XMM, 32 bytes for YMM and 64 bytes for ZMM. When EBX/RBX register is used in inline ASM, the necessary stack frame alignment may become unenforceable and hence vectorization attempts will stop.
Examples:
void foo(int *A, int *B, int n){
int i;
__asm {
push rbx
mov ebx, eax
}
for (i=0;i<n;i++){
B[i] += A[i];
}
__asm {
pop rbx
}
}
$ icpc -c -vec-report2 test58.cc -fasm-blocks -xAVX
test58.cc(1): (col. 32) remark: routine skipped: no vectorization candidates