Technical data

Chapter 2: Storage Mapping

To use this method, keep the Fortran front end from padding data to force

alignment by compiling your program with one of two options to f77.

• Use the –align8 option if your program expects no restrictions on

alignment.

• Use the –align16 option if your program expects to be run on a machine

that requires half-word alignment.

You must also use the misalignment trap handler. This requires minor source

code changes to initialize the handler and the addition of the handler binary

to the link step (see the ﬁxade(3f) man page).

Accessing Misaligned Data Without Modifying Source

Use the second method for programs with widespread misalignment or

whose source may not be modiﬁed.

In this method, a set of special instructions is substituted by the IRIS-4D

assembler for data accesses whose alignment cannot be guaranteed. The

generation of these more forgiving instructions may be opted for each source

ﬁle.

You can invoke this method by specifying of one of the alignment options

(–align8, –align16) to f77 when compiling any source ﬁle that references

misaligned data (see the f77(1) man page). If your program passes

misaligned data to system libraries, you might also need to link it with the

trap handler. See the ﬁxade(3f) man page for more information.