In AArch32, the floating point control and status bits are all in a single register, FPSCR. In AArch64, these were split into separate FPCR and FPSR registers, but the bit layouts remained the same, with no overlaps, so that you could construct an FPSCR value by ORing FPCR and FPSR, or equivalently could produce FPSR and FPCR by masking an FPSCR value. For QEMU's implementation, we opted to use masking to produce FPSR and FPCR, because we started with an AArch32 implementation of FPSCR.
The addition of the (AArch64-only) FEAT_AFP adds new bits to the FPCR which overlap with some bits in the FPSR. This means we'll no longer be able to consider the FPSCR-encoded value as the primary one, but instead need to treat FPSR/FPCR as the primary encoding and construct the FPSCR from those. (This remains possible because the FEAT_AFP bits in FPCR don't appear in the FPSCR.) This patchseries does the necessary refactoring to our handling of FPCR and FPSR to allow us to implement the new FPCR-only bits: * we flip vfp_{get,set}_fpscr() and vfp_{get,set}_{fpcr,fpsr}() so that the former call the latter rather than the other way round * we make the migration code send FPSR and FPCR separately when there's a bit set which can't be represented in the FPSCR format (we continue to use the FPSCR format on the wire when possible, for migration backwards-compatibility) * we store the FPCR and FPSR in the CPU state struct in new vfp.fpcr and vfp.fpsr fields, rather than in vfp.xregs[ARM_VFP_FPSCR] * we make sure that writes to FPSCR leave bits in FPCR that aren't in FPSCR alone The series also has a bit of tidyup of some of the macro naming etc. thanks -- PMM Peter Maydell (9): target/arm: Correct comments about M-profile FPSCR target/arm: Make vfp_get_fpscr() call vfp_get_{fpcr,fpsr} target/arm: Make vfp_set_fpscr() call vfp_set_{fpcr,fpsr} target/arm: Support migration when FPSR/FPCR won't fit in the FPSCR target/arm: Implement store_cpu_field_low32() macro target/arm: Store FPSR and FPCR in separate CPU state fields target/arm: Rename FPCR_ QC, NZCV macros to FPSR_ target/arm: Rename FPSR_MASK and FPCR_MASK and define them symbolically target/arm: Allow FPCR bits that aren't in FPSCR target/arm/cpu.h | 109 ++++++++++++----- target/arm/tcg/translate-a32.h | 7 ++ target/arm/tcg/translate.h | 3 +- target/arm/machine.c | 135 ++++++++++++++++++++- target/arm/tcg/mve_helper.c | 12 +- target/arm/tcg/translate-m-nocp.c | 22 ++-- target/arm/tcg/translate-vfp.c | 4 +- target/arm/vfp_helper.c | 187 +++++++++++++++++++----------- 8 files changed, 356 insertions(+), 123 deletions(-) -- 2.34.1