Exception Handling ABI for the ARM Architecture

Exception handling ABI for the ARM architecture
Table 1, Behaviour of _Unwind_VRS_Set
Regclass Representation Regno Behaviour
_UVRSC_CORE _UVRSD_UINT32 0-15 Internally casts valuep to (uint32_t *) and sets the value of
core register regno to the pointed-to value.
_UVRSC_VFP _UVRSD_VFPX 0-15 Performs an FLDMX from the pointed-to memory to VFP
register D.
_UVRSC_VFP _UVRSD_FLOAT 0-31 Internally casts valuep to (float *) and sets the value of
VFP register S to the pointed-to value as if by
FMSR.
_UVRSC_VFP _UVRSD_UINT32 0-31 Internally casts valuep to (uint32_t *) and sets the value of
VFP register S to the pointed-to value as if by
FMSR. (This operation has effects identical with
(_UVRSC_VFP, _UVRSD_FLOAT))
_UVRSC_VFP _UVRSD_DOUBLE 0-31 Internally casts valuep to (double *) and sets the value of
VFP register D to the pointed-to value as if by
FMDHR,FMDLR.
_UVRSC_WMMXD _UVRSD_UINT64 0-15 Internally casts valuep to (uint64_t *) and sets the value of
WMMX data register regno to the pointed-to value.
_UVRSC_WMMXC _UVRSD_UINT32 0-3 Internally casts valuep to (uint32_t *) and sets the value of
WMMX control register regno to the pointed-to value.
If a call is made with a (regclass, representation) pair not in the above table, the behaviour and return code are
undefined.
Note A given implementation is not required to implement all the above pairs. Calls featuring an
unimplemented pair should yield return code _UVRSR_NOT_IMPLEMENTED. The (_UVRSC_CORE,
_UVRSD_UINT32) pair must always be implemented.
7.5.3 Reading from VRS registers
Only a subset of the assignment representations are supported because usually the content of floating point
registers is unknown.
_Unwind_VRS_Result _Unwind_VRS_Get(_Unwind_Context *context,
_Unwind_VRS_RegClass regclass,
uint32_t regno,
_Unwind_VRS_DataRepresentation representation,
void *valuep);
Valuep must be a pointer to suitably aligned memory. The return code conveys a meaning as follows:
_UVRSR_OK:
Operation succeeded.
_UVRSR_NOT_IMPLEMENTED: Operation not implemented.
_UVRSR_FAILED:
Operation failed in some unspecified way.
The behaviour is determined by examining the regclass and representation and is explained in the table below.
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