The above are pure subsets of valid RVV VCFG configurations (and hence forward compatible between RVP and RVV, whilst also keeping RVP simple). Other useful element types are fixed point fraction types and small integer(4 bit to 7 bit) elements. However these are omitted for now as they aren’t currently part of RVV spec, and the intention of this proposal is to harmonise the Andes SIMD instructions into a subset of RVV.
[[Comparative analysis Harmonised RVP vs Andes Packed SIMD ISA proposal]]
-
-# Comparative analysis with Andes Packed ISA proposal
-
-## 16-bit Arithmetic
-
-| Andes Mnemonic | 16-bit Instruction | Harmonised RVP Equivalent |
-| ------------------ | ------------------------- | ------------------- |
-| ADD16 rt, ra, rb | Add | VADD (r16 <= rt,ra,rb <= r29), mm=00|
-| RADD16 rt, ra, rb | Signed Halving add | RADD (r16 <= rt,ra,rb <= r23), mm=00|
-| URADD16 rt, ra, rb | Unsigned Halving add | RADD (r24 <= rt,ra,rb <= r29), mm=00|
-| KADD16 rt, ra, rb | Signed Saturating add | VADD (r16 <= rt,ra,rb <= r23), mm=01|
-| UKADD16 rt, ra, rb | Unsigned Saturating add | VADD (r24 <= rt,ra,rb <= r29), mm=01|
-| SUB16 rt, ra, rb | Subtract | VSUB (r16 <= rt,ra,rb <= r29), mm=00|
-| RSUB16 rt, ra, rb | Signed Halving sub | RSUB (r16 <= rt,ra,rb <= r23), mm=00|
-| URSUB16 rt, ra, rb | Unsigned Halving sub | RSUB (r24 <= rt,ra,rb <= r29), mm=00|
-| KSUB16 rt, ra, rb | Signed Saturating sub | VSUB (r16 <= rt,ra,rb <= r23), mm=01|
-| UKSUB16 rt, ra, rb | Unsigned Saturating sub | VSUB (r24 <= rt,ra,rb <= r29), mm=01|
-| CRAS16 rt, ra, rb | Cross Add & Sub | |
-| RCRAS16 rt, ra, rb | Signed Halving Cross Add & Sub | |
-| URCRAS16 rt, ra, rb| Unsigned Halving Cross Add & Sub | |
-| KCRAS16 rt, ra, rb | Signed Saturating Cross Add & Sub | |
-| UKCRAS16 rt, ra, rb| Unsigned Saturating Cross Add & Sub | |
-| CRSA16 rt, ra, rb | Cross Sub & Add | |
-| RCRSA16 rt, ra, rb | Signed Halving Cross Sub & Add | |
-| URCRSA16 rt, ra, rb| Unsigned Halving Cross Sub & Add | |
-| KCRSA16 rt, ra, rb | Signed Saturating Cross Sub & Add | |
-| UKCRSA16 rt, ra, rb| Unsigned Saturating Cross Sub & Add | |
-
-## 8-bit Arithmetic
-
-| Andes Mnemonic | 8-bit Instruction | Harmonised RVP Equivalent |
-| ------------------ | ------------------------- | ------------------- |
-| ADD8 rt, ra, rb | Add | VADD (r2 <= rt,ra,rb <= r15), mm=00 |
-| RADD8 rt, ra, rb | Signed Halving add | RADD (r2 <= rt,ra,rb <= r7), mm=00 |
-| URADD8 rt, ra, rb | Unsigned Halving add | RADD (r8 <= rt,ra,rb <= r15), mm=00 |
-| KADD8 rt, ra, rb | Signed Saturating add | VADD (r2 <= rt,ra,rb <= r7), mm=01 |
-| UKADD8 rt, ra, rb | Unsigned Saturating add | VADD (r8 <= rt,ra,rb <= r15), mm=01 |
-| SUB8 rt, ra, rb | Subtract | VSUB (r2 <= rt,ra,rb <= r15), mm=00 |
-| RSUB8 rt, ra, rb | Signed Halving sub | RSUB (r2 <= rt,ra,rb <= r7), mm=00 |
-| URSUB8 rt, ra, rb | Unsigned Halving sub | RSUB (r8 <= rt,ra,rb <= r15), mm=00 |
-| KSUB8 rt, ra, rb | Signed Saturating sub | VSUB (r2 <= rt,ra,rb <= r7), mm=01 |
-| UKSUB8 rt, ra, rb | Unsigned Saturating sub | VSUB (r8 <= rt,ra,rb <= r15), mm=01 |
-
-## 16-bit Shifts
-
-SRA[I]16/SRL[I]16/SLL[I]16 to be mapped to VOP shift instructions in same manner as ADD16/SUB16
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-The “K” (Saturation) and “u” (Rounding) variants could be encoded using VOP’s mm field (mm=01 is saturated or rounded shift, mm=00 is standard VOP shift)
-
-| Andes Mnemonic | 16-bit Instruction | Harmonised RVP Equivalent |
-| ------------------ | ------------------------- | ------------------- |
-| SRA16 rt, ra, rb | Shift right arithmetic | VSRA (r16 <= rt,ra,rb <= r29), mm=00|
-| SRAI16 rt, ra, im | Shift right arithmetic imm | VSRAI (r16 <= rt,ra <= r29), mm=00|
-| SRA16.u rt, ra, rb | Rounding Shift right arithmetic | VSRA (r16 <= rt,ra,rb <= r29), mm=01|
-| SRAI16.u rt, ra, im | Rounding Shift right arithmetic imm | VSRAI (r16 <= rt,ra <= r29), mm=01|
-| SRL16 rt, ra, rb | Shift right logical | VSRL (r16 <= rt,ra,rb <= r29), mm=00|
-| SRLI16 rt, ra, im | Shift right logical imm | VSRLI (r16 <= rt,ra <= r29), mm=00|
-| SRL16.u rt, ra, rb | Rounding Shift right logical | VSRL (r16 <= rt,ra,rb <= r29), mm=01|
-| SRLI16.u rt, ra, im | Rounding Shift right logical imm | VSLRI (r16 <= rt,ra <= r29), mm=01|
-| SLL16 rt, ra, rb | Shift left logical | VSLL (r16 <= rt,ra,rb <= r29), mm=00|
-| SLLI16 rt, ra, im | Shift left logical imm | VSLLI (r16 <= rt,ra <= r29), mm=00|
-| KSLL16 rt, ra, rb | Saturating Shift left logical | VSLL (r16 <= rt,ra,rb <= r29), mm=01|
-| KSLLI16 rt, ra, im | Saturating Shift left logical imm | VSLLI (r16 <= rt,ra <= r29), mm=01|
-| KSLRA16 rt, ra, rb | Saturating Shift left logical or Shift right arithmetic ||
-| KSLRA16.u rt, ra, rb | Saturating Shift left logical or Rounding Shift right arithmetic ||
-
-
-## 8-bit Shifts
-
-Andes SIMD Packed ISA omits 8 bit shifts, but these can be encoded in Harmonised RVP as follows:
-
-| Andes Mnemonic | 8-bit Instruction | Harmonised RVP Equivalent |
-| ------------------ | ------------------------- | ------------------- |
-| n/a | Shift right arithmetic | VSRA (r2 <= rt,ra,rb <= r15), mm=00|
-| n/a | Shift right arithmetic imm | VSRAI (r2 <= rt,ra <= r15), mm=00|
-| n/a | Rounding Shift right arithmetic | VSRA (r2 <= rt,ra,rb <= r15), mm=01|
-| n/a | Rounding Shift right arithmetic imm | VSRAI (r2 <= rt,ra <= r15), mm=01|
-| n/a | Shift right logical | VSRL (r2 <= rt,ra,rb <= r15), mm=00|
-| n/a | Shift right logical imm | VSRLI (r2 <= rt,ra <= r15), mm=00|
-| n/a | Rounding Shift right logical | VSRL (r2 <= rt,ra,rb <= r15), mm=01|
-| n/a | Rounding Shift right logical imm | VSLRI (r2 <= rt,ra <= r15), mm=01|
-| n/a | Shift left logical | VSLL (r2 <= rt,ra,rb <= r15), mm=00|
-| n/a | Shift left logical imm | VSLLI (r2 <= rt,ra <= r15), mm=00|
-| n/a | Saturating Shift left logical | VSLL (r2 <= rt,ra,rb <= r15), mm=01|
-| n/a | Saturating Shift left logical imm | VSLLI (r2 <= rt,ra <= r15), mm=01|
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