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comparison doc/manual/callconvs/callconv_arm32.tex @ 404:524fdca405bf
- some doc/manual callconv clarifications for arm
| author | Tassilo Philipp |
|---|---|
| date | Wed, 07 Apr 2021 18:39:46 +0200 |
| parents | 06c9adae114d |
| children | b47168dacba6 |
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| 403:a3e47b7c808c | 404:524fdca405bf |
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| 89 \item first four words are passed using r0-r3 | 89 \item first four words are passed using r0-r3 |
| 90 \item subsequent parameters are pushed onto the stack (in right to left order, such that the stack pointer points to the first of the remaining parameters) | 90 \item subsequent parameters are pushed onto the stack (in right to left order, such that the stack pointer points to the first of the remaining parameters) |
| 91 \item if the callee takes the address of one of the parameters and uses it to address other parameters (e.g. varargs) it has to copy - in its prolog - the first four words to a reserved stack area adjacent to the other parameters on the stack | 91 \item if the callee takes the address of one of the parameters and uses it to address other parameters (e.g. varargs) it has to copy - in its prolog - the first four words to a reserved stack area adjacent to the other parameters on the stack |
| 92 \item parameters \textless=\ 32 bits are passed as 32 bit words | 92 \item parameters \textless=\ 32 bits are passed as 32 bit words |
| 93 \item 64 bit parameters are passed as two 32 bit parts (even partly via the register and partly via the stack, although this doesn't seem to be specified in the ATPCS) | 93 \item 64 bit parameters are passed as two 32 bit parts (even partly via the register and partly via the stack, although this doesn't seem to be specified in the ATPCS) |
| 94 \item structures and unions are passed by value, with the first four words of the parameters in r0-r3 | 94 \item structures and unions are passed by value (after rounding up the size to the nearest multiple of 4), as a sequence of words |
| 95 \item if return value is a structure, a pointer pointing to the return value's space is passed in r0, the first parameter in r1, etc... (see {\bf return values}) | 95 \item if return value is a structure, a pointer pointing to the return value's space is passed in r0, the first parameter in r1, etc... (see {\bf return values}) |
| 96 \item keeping the stack eight-byte aligned can improve memory access performance and is required by LDRD and STRD on ARMv5TE processors which are part of the ARM32 family, so, in order to avoid problems one should always align the stack (tests have shown, that GCC does care about the alignment when using the ellipsis) | 96 \item keeping the stack eight-byte aligned can improve memory access performance and is required by LDRD and STRD on ARMv5TE processors which are part of the ARM32 family, so, in order to avoid problems one should always align the stack (tests have shown, that GCC does care about the alignment when using the ellipsis) |
| 97 \end{itemize} | 97 \end{itemize} |
| 98 | 98 |
| 99 \paragraph{Return values} | 99 \paragraph{Return values} |
| 179 \item first four words are passed using r0-r3 | 179 \item first four words are passed using r0-r3 |
| 180 \item subsequent parameters are pushed onto the stack (in right to left order, such that the stack pointer points to the first of the remaining parameters) | 180 \item subsequent parameters are pushed onto the stack (in right to left order, such that the stack pointer points to the first of the remaining parameters) |
| 181 \item if the callee takes the address of one of the parameters and uses it to address other parameters (e.g. varargs) it has to copy - in its prolog - the first four words to a reserved stack area adjacent to the other parameters on the stack | 181 \item if the callee takes the address of one of the parameters and uses it to address other parameters (e.g. varargs) it has to copy - in its prolog - the first four words to a reserved stack area adjacent to the other parameters on the stack |
| 182 \item parameters \textless=\ 32 bits are passed as 32 bit words | 182 \item parameters \textless=\ 32 bits are passed as 32 bit words |
| 183 \item 64 bit parameters are passed as two 32 bit parts (even partly via the register and partly via the stack), although this doesn't seem to be specified in the ATPCS) | 183 \item 64 bit parameters are passed as two 32 bit parts (even partly via the register and partly via the stack), although this doesn't seem to be specified in the ATPCS) |
| 184 \item structures and unions are passed by value, with the first four words of the parameters in r0-r3 | 184 \item structures and unions are passed by value (after rounding up the size to the nearest multiple of 4), as a sequence of words |
| 185 \item if return value is a structure, a pointer pointing to the return value's space is passed in r0, the first parameter in r1, etc. (see {\bf return values}) | 185 \item if return value is a structure, a pointer pointing to the return value's space is passed in r0, the first parameter in r1, etc. (see {\bf return values}) |
| 186 \item keeping the stack eight-byte aligned can improve memory access performance and is required by LDRD and STRD on ARMv5TE processors which are part of the ARM32 family, so, in order to avoid problems one should always align the stack (tests have shown, that GCC does care about the alignment when using the ellipsis) | 186 \item keeping the stack eight-byte aligned can improve memory access performance and is required by LDRD and STRD on ARMv5TE processors which are part of the ARM32 family, so, in order to avoid problems one should always align the stack (tests have shown, that GCC does care about the alignment when using the ellipsis) |
| 187 \end{itemize} | 187 \end{itemize} |
| 188 | 188 |
| 189 \paragraph{Return values} | 189 \paragraph{Return values} |
| 375 \item subsequent parameters are pushed onto the stack (in right to left order, such that the stack pointer points to the first of the remaining parameters) | 375 \item subsequent parameters are pushed onto the stack (in right to left order, such that the stack pointer points to the first of the remaining parameters) |
| 376 \item note that as soon one floating point parameter is passed via the stack, subsequent single precision floating point parameters are also pushed onto the stack even if there are still free S* registers | 376 \item note that as soon one floating point parameter is passed via the stack, subsequent single precision floating point parameters are also pushed onto the stack even if there are still free S* registers |
| 377 \item float and double vararg function parameters (no matter if in ellipsis part of function, or not) are passed like int or long long parameters, vfp registers aren't used | 377 \item float and double vararg function parameters (no matter if in ellipsis part of function, or not) are passed like int or long long parameters, vfp registers aren't used |
| 378 \item if the callee takes the address of one of the parameters and uses it to address other parameters (e.g. varargs) it has to copy - in its prolog - the first four words (for first 4 integer arguments) to a reserved stack area adjacent to the other parameters on the stack | 378 \item if the callee takes the address of one of the parameters and uses it to address other parameters (e.g. varargs) it has to copy - in its prolog - the first four words (for first 4 integer arguments) to a reserved stack area adjacent to the other parameters on the stack |
| 379 \item parameters \textless=\ 32 bits are passed as 32 bit words | 379 \item parameters \textless=\ 32 bits are passed as 32 bit words |
| 380 \item structures and unions are passed by value, with the first four words of the parameters in r0-r3 | 380 \item structures and unions are passed by value (after rounding up the size to the nearest multiple of 4), as a sequence of words |
| 381 \item if return value is a structure, a pointer pointing to the return value's space is passed in r0, the first parameter in r1, etc. (see {\bf return values}) | 381 \item if return value is a structure, a pointer pointing to the return value's space is passed in r0, the first parameter in r1, etc. (see {\bf return values}) |
| 382 \item callee spills, caller reserves spill area space, though | 382 \item callee spills, caller reserves spill area space, though |
| 383 \end{itemize} | 383 \end{itemize} |
| 384 | 384 |
| 385 \paragraph{Return values} | 385 \paragraph{Return values} |