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dev:crosscompiler:backend_arm:register_allocation [2018/12/11 17:27] – [Register Usage] ursgraf | dev:crosscompiler:backend_arm:register_allocation [2019/08/29 16:02] – [Parameter Passing] ursgraf | ||
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===== Register Usage ===== | ===== Register Usage ===== | ||
- | Registers can be classified as // | ||
| Register | State | Use | | | Register | State | Use | | ||
- | | R0 | volatile | 1st. parameter, return value | | + | | R0 | volatile | 1st. parameter, local variables, return value | |
- | | R1 | volatile | 2nd. parameter, return value (if long, lower 4 bytes of long) | | + | | R1 | volatile | 2nd. parameter, local variables, return value (if long, lower 4 bytes of long) | |
| R2-R5 | volatile | further parameters, local variables | | | R2-R5 | volatile | further parameters, local variables | | ||
| R6 | dedicated | scratch register | | | R6 | dedicated | scratch register | | ||
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| R15 | dedicated | PC | | | R15 | dedicated | PC | | ||
| D0 | dedicated| scratch register | | | D0 | dedicated| scratch register | | ||
- | | D1 | volatile | + | | D1 | dedicated| scratch register, return value | |
- | | D2-D6 | volatile | further | + | | D2-D6 | volatile | parameters, local variables |
| D7-D10 | volatile | local variables | | | D7-D10 | volatile | local variables | | ||
| D11-D31 | nonvolatile | local variables | | | D11-D31 | nonvolatile | local variables | | ||
| S0,S1 | dedicated| scratch register | | | S0,S1 | dedicated| scratch register | | ||
- | | S2 | volatile | 1. parameter, return value | | + | | S2 | volatile | 1. parameter, local variables, return value | |
- | | S3-S6 | volatile | further parameters | | + | | S3-S13 | volatile | further parameters, local variables |
- | | S7-D21 | volatile | local variables | | + | | S14-S21 | volatile | local variables | |
| S22-S31 | nonvolatile | local variables | | | S22-S31 | nonvolatile | local variables | | ||
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For the translation of certain SSA instructions (e.g. of type long) further auxiliary registers are needed. They are assigned and reserved by the register allocator as well. | For the translation of certain SSA instructions (e.g. of type long) further auxiliary registers are needed. They are assigned and reserved by the register allocator as well. | ||
- | ==== Parameter Passing ==== | + | ===== Parameter Passing |
- | Parameters are passed in R0..R5 and D1..D6.\\ | + | Parameters are passed in R0..R5 and D2..D6.\\ |
- | In the interface //armPPC/ | + | In the interface //arm/ |
+ | |S0|S1|S2|S3|S4|S5|S6|S7|S8|S9|S10|S11| | ||
+ | | D0 || D1 || D2 || D3 || D4 || D5 || | ||
+ | | ^| ^^a| ^ b ^^c| ^ d ^^ | ||
- | ==== Locals on the Stack ==== | + | ===== Locals on the Stack ===== |
Most SSA instruction have 2 operands and a result. Each of them can reside on the stack. Operands must be fetched into a free register, the result must be stored onto the stack. A single SSA instruction '' | Most SSA instruction have 2 operands and a result. Each of them can reside on the stack. Operands must be fetched into a free register, the result must be stored onto the stack. A single SSA instruction '' | ||
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+ | When dividing numbers of type long, a large number of auxiliary registers are necessary. For these cases the register allocation is run with a reduced register set with the same reserved registers as above given above. |