The use of extended precision in CVF should be mostly matched by 32-bit ifort with setting of IA32 instruction set. As these applications are normally run with x87 precision set (by default with CVF and ifort) to 53 bits, it is equivalent to promoting intermediate calculations with REAL(x,REAL64) or, in F77, dble(). As Steve pointed out, you have no control over where CVF or ifort do this automatically for the "IA32" target,and ifort may not exactly match CVF.
If you wish to take the trouble, you may insert explicit promotions in your code for each expression involving 3 or more operands. Due to the mixed data type promotion rules of Fortran, one insertion of dble() will take care of a 3 operand expression in some cases (like A*REAL(X,REAL64)+B). Of course, this REAL64 (if you don't define it yourself) depends on USE ISO_FORTRAN_ENV, which ifort has supported in recent years. You could make up your own named module or internal function to abbreviate the verbose REAL intrinsic while improving future portabiity compared with DBLE(). Then you could expect portability to Intel64 targets. It may be necessary, or at least helpful, to declare all local scalar variables as REAL(REAL64). REAL(8) would work with ifort compatible compilers, but it is poor style.
When using simd instruction sets, which you probably are doing, as ifort defaults to /arch:SSE2, mixed single and double precision are likely to reduce performance, hence the preference of previous replies to suggest full doube precision.
