Gental ping. On 2026-07-09 00:18, Max Chou wrote: > This patchset adds support for the RISC-V Zvfofp8min ISA extension that > provides conversion operations for OCP FP8 formats which provide the > foundation for the future vector matrix extensions. > > Ratification status: > - Zvfofp8min is currently v0.9 and is going through the RVIA ratification > process. This series tracks the v0.9 isa-manual tag below. > - riscv-isa-manual tag: > https://github.com/riscv/riscv-isa-manual/releases/tag/zvfofp8min-0.9 > > Zvfofp8min (v0.9): > - The Zvfofp8min extension provides minimal vector conversion support for > the OFP8 formats. It requires the Zve32f extension and leverages the > altfmt field in the VTYPE CSR (introduced by Zvfbfa) to select between > E4M3 (altfmt=0) and E5M2 (altfmt=1) formats. Per the OCP FP8 spec and > the extension definition: > - Canonical NaN for both E4M3 and E5M2 is 0x7f. > - All NaNs are treated as quiet NaNs. > - Widening conversions are exact: no rounding and no exception flags. > - These conversions are the data-movement primitives that feed and drain > the OFP8 vector/matrix compute pipeline. > - The LLVM RISC-V backend emits these instructions as of LLVM 22.1.0: > > https://releases.llvm.org/22.1.0/docs/ReleaseNotes.html#changes-to-the-risc-v-backend > > Instructions: > Extended (existing instructions taught to handle OFP8): > - vfwcvtbf16.f.f.v : OFP8 to BF16 widening conversion > - vfncvtbf16.f.f.w : BF16 to OFP8 narrowing conversion > New: > - vfncvtbf16.sat.f.f.w : BF16 to OFP8 narrowing with saturation > - vfncvt.f.f.q : FP32 to OFP8 quad-width (4x) narrowing conversion > - vfncvt.sat.f.f.q : FP32 to OFP8 quad-width narrowing with saturation > > Verification: > - riscv-tests (fork https://github.com/riscv-software-src/riscv-tests): > https://github.com/rnax/riscv-tests/tree/dev/rnax/support_zvfofp8min > - Require LLVM 22.1.0 > > https://releases.llvm.org/22.1.0/docs/ReleaseNotes.html#changes-to-the-risc-v-backend > - Zvfofp8min test target: rv64uzvfofp8min/rv32uzvfofp8min > - Both Spike and QEMU applied this patchset could pass the riscv-tests > > References: > - OCP FP8 specification: > > https://www.opencompute.org/documents/ocp-8-bit-floating-point-specification-ofp8-revision-1-0-2023-12-01-pdf-1 > > > Changes in v6 > - Add patch 1 to fix the biased exponent write bug in the > parts_float_to_e5m2() saturate path. FloatParts64.exp holds an > unbiased exponent, so exp_bias must be subtracted when storing > the max-normal biased exponent value. > - Initialize float_e4m3_nan_is_snan to false in riscv_cpu_reset_hold() > to ensure consistent NaN handling for OFP8 E4M3 operations. > - Merge "Expose Zvfofp8min property" into "Add cfg property for > Zvfofp8min extension" to keep the property registration together > with the cfg field definition. > - Fix indentation of cbo.* opcode table entries in the disas patch. > - Rebase on riscv-to-apply.next (commit 267b5a2) > > Changes in v5 > - Drop Zvfofp4min which is not going through the RVIA ratification > process yet. > - Fix typos. > - Rebase on riscv-to-apply.next (commit bf76a00) > > Changes in v4 > - Rebase on riscv-to-apply.next (commit 21101a7) > - Remove the softfloat library related patches (Thanks for RH's help to > split this part) > - Add missing illegal ALTFMT SEW pattern checking for Zvfofp8min in > patch 4 (target/riscv: rvv: Make vfwcvtbf16.f.f.v support OFP8 to BF16 > conversion for Zvfofp8min extension) > > Changes in v3 > - Add floatN_nan_is_snan to simply the quiet/signaling NaN checking flow > in patch 2 & 3 > - Add patch 4 to fix pseudo-NaN handling in FPATAN/FYL2XP1/FYL2X helpers > > Changes in v2 > - Merged v1 patch 2 & 3 to v2 patch 3, v1 patch 4 & 5 to v2 patch 4 > - Added new v2 patch 2 to refactor the IEEE format NaN classification > functions (float16, bfloat16, float32, float64) to use internal helper > functions, reducing code duplication and improving maintainability. > The OCP FP8 NaN classification functions follow the same pattern. > - Refactored softfloat implementation to use capability-based FloatFmt > flags (no_infinity, limited_nan, overflow_raises_invalid, normal_frac_max) > instead of monolithic flags > - Removed ocp_fp8e5m2_no_signal_nan and ocp_fp8_same_canonical_nan flags > from float_status; now using local float_status with no_signaling_nans > and default_nan_pattern for RISC-V Zvfofp8min instructions > - Rebased on latest riscv-to-apply.next with zvfbfa v3 patchset > > v5: [email protected] > v4: [email protected] > v3: [email protected] > v2: [email protected] > v1: [email protected] > > > Max Chou (9): > fpu: Fix biased exponent write in parts_float_to_e5m2 saturate path > target/riscv: rvv: Fix NOP_UU_B vs2 width > target/riscv: Add cfg property for Zvfofp8min extension > target/riscv: Add implied rules for Zvfofp8min extension > target/riscv: rvv: Make vfwcvtbf16.f.f.v support OFP8 to BF16 > conversion for Zvfofp8min extension > target/riscv: rvv: Make vfncvtbf16.f.f.w support BF16 to OFP8 > conversion for Zvfofp8min extension > target/riscv: rvv: Add vfncvtbf16.sat.f.f.w instruction for Zvfofp8min > extension > target/riscv: rvv: Add vfncvt.f.f.q and vfncvt.sat.f.f.q instructions > for Zvfofp8min extension > disas/riscv: Add support of Zvfofp8min extension > > disas/riscv.c | 19 ++- > fpu/softfloat.c | 3 +- > target/riscv/cpu.c | 13 +- > target/riscv/cpu_cfg_fields.h.inc | 1 + > target/riscv/helper.h | 12 ++ > target/riscv/insn32.decode | 5 + > .../riscv/tcg/insn_trans/trans_rvbf16.c.inc | 32 +++-- > .../riscv/tcg/insn_trans/trans_rvofp8.c.inc | 105 +++++++++++++++ > target/riscv/tcg/insn_trans/trans_rvv.c.inc | 40 ++++++ > target/riscv/tcg/tcg-cpu.c | 5 + > target/riscv/tcg/translate.c | 1 + > target/riscv/tcg/vector_helper.c | 120 +++++++++++++++++- > 12 files changed, 338 insertions(+), 18 deletions(-) > create mode 100644 target/riscv/tcg/insn_trans/trans_rvofp8.c.inc > > -- > 2.55.0 >
