[M3devel] integer overflow

[Jay K]

Been reading about Alpha:


Alpha and Programming Languages 
Alpha is an attractive architecture for compiling a large variety of programming languages. 
Alpha has been carefull y desi gned to avoi d bi as t oward one or two progra mmi ng languages. 
For example: 
• Alpha does not contain a subroutine call instruction that moves a register window by a 
fixed amount. Thus, Alpha is a good match for programming languages with many 
parameters and programming languages with no parameters. 
• Alpha does not contain a global integer overflow enable bit. Such a bit would need to 
be changed at every subroutine boundary when a FORTRAN program calls a C pro- 
gram. 







...


Integer Operate Instructions 
...Integer overfl ow tr ap enable is encoded in t he functi on fie ld of ea ch instruct ion, ra ther t han 
kept in a global state bit. Thus, for example, both ADDQ/V and ADDQ opcodes exist for spec- 
ifying 64-bi t ADD with and without overflow checking. That makes it easier to pipe line 
implementations. 



 - Jay