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| META TOPICPARENT |
name="WebHome" |
Calling C Functions from Forth and Vice Versa |
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https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/on-the-aapcs-with-an-application-to-efficient-parameter-passing |
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| Register |
AAPCS Purpose |
MECRISP Forth Purpose |
| r0 |
Argument, result, scratch register 1 |
Scratch |
| r1 |
Argument, result, scratch register 2 |
Scratch |
| r2 |
Argument, scratch register 3 |
Scratch |
| r3 |
Argument, scratch register 4 |
Scratch |
| r4 |
Variable register 1 |
DO Index |
| r5 |
Variable register 2 |
DO Limit |
| r6 |
Variable register 3 |
Top Of Stack TOS |
| r7 |
Variable register 4 |
Data stack pointer |
| r8 |
Variable register 5 |
unused |
| r9 |
Platform register (usage defined by platform in use) |
unused |
| r10 |
Variable register 7 |
unused |
| r11 |
Variable register 8 |
unused |
| r12 |
Intra-procedure-call scratch register |
unused |
| r13 |
Stack pointer (SP) |
Stack pointer (SP) |
| r14 |
Link register (LR) |
Link register (LR) |
| r15 |
Program counter (PC) |
Program counter (PC) |
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| Register |
AAPCS Purpose |
MECRISP Forth Purpose |
ISR Stacking |
| xPSR |
Processor Status Register, Flags |
Flags |
1 |
| r0 |
Argument, result, scratch register 1 |
Scratch |
2 |
| r1 |
Argument, result, scratch register 2 |
Scratch |
3 |
| r2 |
Argument, scratch register 3 |
Scratch |
4 |
| r3 |
Argument, scratch register 4 |
Scratch |
5 |
| r4 |
Variable register 1 |
DO Index |
|
| r5 |
Variable register 2 |
DO Limit |
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| r6 |
Variable register 3 |
Top Of Stack TOS |
|
| r7 |
Variable register 4 |
Data stack pointer |
|
| r8 |
Variable register 5 |
unused |
|
| r9 |
Platform register (usage defined by platform in use) |
unused |
|
| r10 |
Variable register 7 |
unused |
|
| r11 |
Variable register 8 |
unused |
|
| r12 |
Intra-procedure-call scratch register |
unused |
6 |
| r13 |
Stack pointer (SP) |
Stack pointer (SP) |
|
| r14 |
Link register (LR) |
Link register (LR) |
7 |
| r15 |
Program counter (PC) |
Program counter (PC) |
0 |
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VFP Register Usage
The VFP-v2 co-processor has 32 single-precision registers, s0-s31, which may also be accessed as 16 |
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