Zcmp Extension
Synopsis
The Zcmp extension is a set of instructions which may be executed as a series of existing 32-bit RISC-V instructions.
This extension reuses some encodings from c.fsdsp. Therefore it is incompatible with [Zcd], which is included when C and D extensions are both present.
| Zcmp is primarily targeted at embedded class CPUs due to implementation complexity. Additionally, it is not compatible with architecture class profiles. |
The Zcmp extension depends on the [Zca] extension.
The PUSH/POP assembly syntax uses several variables, the meaning of which are:
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reg_list is a list containing 1 to 13 registers (ra and 0 to 12 s registers)
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valid values: {ra}, {ra, s0}, {ra, s0-s1}, {ra, s0-s2}, …, {ra, s0-s8}, {ra, s0-s9}, {ra, s0-s11}
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note that {ra, s0-s10} is not valid, giving 12 lists not 13 for better encoding
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stack_adj is the total size of the stack frame.
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valid values vary with register list length and the specific encoding, see the instruction pages for details.
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| RV32 | RV64 | Mnemonic | Instruction |
|---|---|---|---|
yes |
yes |
cm.push {reg_list}, -stack_adj |
|
yes |
yes |
cm.pop {reg_list}, stack_adj |
|
yes |
yes |
cm.popret {reg_list}, stack_adj |
|
yes |
yes |
cm.popretz {reg_list}, stack_adj |
|
yes |
yes |
cm.mva01s rs1', rs2' |
|
yes |
yes |
cm.mvsa01 r1s', r2s' |
Instructions
The following instructions are defined by this extension:
Move two s0-s7 registers into a0-a1 |
|
Move a0-a1 into two registers of s0-s7 |
|
Destroy function call stack frame |
|
Destroy function call stack frame and return to |
|
Destroy function call stack frame, move zero to |
|
Create function call stack frame |