IAS applies static analysis to procedure code to automatically generate unwind records. Use this feature when a procedure as an intermediate element must provide safe propagation of the stack unwinding process from the called function to the unwind handler in the caller procedure.
The assembler builds unwind information for all procedures in the file, starting from the procedure’s first entry point and continuing through to .endp.
When the static analysis is not complete; for example, an indirect branch is unaccompanied by branch target annotation, IAS sends a warning message and then attempts to simplify the analysis by assuming that the procedure has one prologue and multiple epilogues. This approach works in most cases. If this is not successful, IAS issues an error message.
The unwind generator is based upon the Itanium(TM) architecture software conventions. See the Software Conventions and Runtime Architecture Guide. Invoke unwind generation using the -X unwind command-line option. When you use this flag, IAS ignores all unwind directives and issues a warning.