User`s guide

How the MACRO Compiler Functions on Different Platforms
2.13 Debugging
• You can deposit floating-point data in an Alpha or Itanium integer register
with the DEPOSIT command. The syntax is the same as it is on a VAX
system.
• H_FLOAT is unsupported.
• On OpenVMS I64 systems, incoming parameters are in R32 through R39, not
in R16 through R21. Outgoing parameters are in higher numbered registers
chosen by the compiler.
2–36 How the MACRO Compiler Functions on Different Platforms