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Register Guide

RISC-V fs5 / f21 Register: Floating saved register

f21/fs5 is a floating-point register used by F/D/Q/Zfh instructions for operands and results.

ABI name: fs5; physical register: f21.
Save rule: Callee, for values no wider than ABI_FLEN.
Read it through its psABI role first, then inspect how each instruction reads or writes it.
Physical Name f21ABI Name fs5Save Rule Callee, for values no wider than ABI_FLEN
Role
Floating saved register
Convention
Preserved across calls only for values no wider than ABI_FLEN
Remember This First
The calling convention listed for this entry is: Preserved across calls only for values no wider than ABI_FLEN.
psABI Floating-Point Register Reference

ABI register

f21/fs5 is a floating-point register used by F/D/Q/Zfh instructions for operands and results.

Preserved across calls: Callee, for values no wider than ABI_FLEN
RISC-V psABI floating-point register convention

When It Fits Best

  • - Use it according to the documented role: Floating saved register.
  • - Consult the applicable ISA or ABI specification for concrete read, write, or execution semantics.

When Not To Use It This Way

  • - Do not apply the integer temporary-register t* rules to this entry.
  • - Do not infer behavior not defined by this page or the applicable specification from the ABI name.

What Happens Around A Call

1

The calling convention listed for this entry is: Preserved across calls only for values no wider than ABI_FLEN.

2

The save rule listed for this entry is: Callee, for values no wider than ABI_FLEN.

Read The Documented Role

Examples explain the rule, not a complete program
# f21 / fs5
# Floating saved register
# Preserved across calls only for values no wider than ABI_FLEN