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Add 32-bit Arm and AArch64 to CallingConventions.md #5308

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Add 32-bit Arm and AArch64 to CallingConventions.md #5308

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50 changes: 50 additions & 0 deletions doc/diagnostics/CallingConventions.md
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Expand Up @@ -239,6 +239,56 @@ Useful links:
* [z/Architecture Principles of Operation](http://publibfi.boulder.ibm.com/epubs/pdf/dz9zr008.pdf)
* [z/Architecture Reference Summary](http://publibfi.boulder.ibm.com/epubs/pdf/dz9zs006.pdf)

# 32-bit Arm

## Linux

Scratch registers are not preserved across calls, while non-volatile registers are preserved by called functions.
Usage of the VFP registers in this table assumes hard-float ABI.

|Register|System Linkage|
|--|--|
|R0|1st argument / return value|
|R1|2nd argument / return value|
|R2-3|3rd-4th arguments|
|R4-10|Non-volatile|
|R11|System Frame Pointer (FP)|
|R12|Scratch; Intra-Procedure-Call Register (IP)|
|R13|System Stack Pointer (SP)|
|R14|Link Register (LR)|
|R15|Program Counter (PC)|
|D0|1st floating point argument / floating point return value|
|D1-7|2nd-8th floating point arguments|
|D8-15|Non-volatile|
|D16-D31|Scratch<sup>1</sup>|

<hr/>

1. Unavailable in some VFP versions

# AArch64 (64-bit Arm)

## Linux

Scratch registers are not preserved across calls, while non-volatile registers are preserved by called functions.

|Register|System Linkage|
|--|--|
|R0|1st argument / return value|
|R1-7|2nd-8th arguments|
|R8-15|Scratch|
|R16-17|Scratch; Intra-Procedure-Call Registers (IP0-1)|
|R18|Scratch; Platform Register|
|R19-28|Non-volatile|
|R29|System Frame Pointer (FP)|
|R30|Link Register (LR)|
|SP|System Stack Pointer|
|PC|Program Counter (PC)|
|V0|1st floating point argument / floating point return value|
|V1-7|2nd-8th floating point arguments|
|V8-15|Non-volatile|
|V16-31|Scratch|

# RISC-V

| Register | System Linkage | Callee Preserved |
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