| base+4 ... base+2 | base | number of bits |
| ------ ----------------- | ---------------- | -------------------------- |
| ..xxxx xxxxxxxxxxxxxxxx | xnnnxxxxx1111111 | (80+16\*nnn)-bit, nnn!=111 |
-| {ops}{Pred}{Reg}{VL Block} | SV Prefix | |
+| {ops}{Pred}{Reg}{VL Block} | VBLOCK Prefix | |
A suitable prefix, which fits the Expanded Instruction-Length encoding
for "(80 + 16 times instruction-length)", as defined in Section 1.5
of the RISC-V ISA, is as follows:
-| 15 | 14:12 | 11:10 | 9:8 | 7 | 6:0 |
-| - | ----- | ----- | ----- | --- | ------- |
-| vlset | 16xil | pplen | rplen | mode | 1111111 |
+| 15 | 14:12 | 11:10 | 9 | 8 | 7 | 6:0 |
+| - | ----- | ----- | ----- | ---- | --- | ------- |
+| vlset | 16xil | rplen | pplen | pmode | rmode | 1111111 |
-The VL/MAXVL/SubVL Block format:
+The VL/MAXVL/SubVL Block format, when 16xil != 0b111, is:
-| 31-30 | 29:28 | 27:22 | 21:17 - 16 |
-| - | ----- | ------ | ------ - - |
-| 0 | SubVL | VLdest | VLEN vlt |
-| 1 | SubVL | VLdest | VLEN |
+[[!table data="""
+31:30 | 29:28 | 27:22 | 21 | 20:19 | 18:16 | comment.................. |
+0b00 | SubVL | imm[5:0] |rsvd| rd[4:0] || sv.setvl rd, x0, imm |
+0b01 | SubVL | imm[5:0] | rs1[2:0] || rd[2:0] | sv.setvl rd, rs1, imm (1) |
+0b10 | SubVL | imm[5:0] |rsvd| rs1[4:0] || sv.setvl x0, rs1, imm |
+0b11 | rsvd | rsvd |rsvd| rsvd || reserved, all 0s |
+"""]]
+Note (1) - Registers are in RVC format (x8-x15)
+
+Note (2) - [[specification/sv.setvl]] behaviour is expected, as if an sv.setvl
+instruction had actually been called.
+
+When 16xil is 0b111, this is the "Extended" Format, using the >= 192-bit
+RISC-V ISA format. Note that the length is 96+16\*nnnnn, not 192+
+
+| base+5 ... base+3 | base+1 | base | no. of bits |
+| ------ ----------------- | | ---------------- | ------------- |
+| ..xxxx xxxxxxxxxxxxxxxx | | x111xxxxx1111111 | 96+16\*nnnnn |
+| {ops}{Pred}{Reg}{VL Block}| VBLOCK2 | VBLOCK Prefix | |
+
+VBLOCK2 extends the VBLOCK fields:
+
+| 15 | 14:12 | 11:10 | 9:8 | 7:5 | 4:0 |
+| ---- | ----- | ----- | ---- | --- | ---- |
+| rsvd | mapsz | rplen2 | pplen2 | swlen | ilen |
+
+* ilen is the instruction length (number of 16-bit blocks)
+* swlen specifies the number of "swizzle" blocks
+* rplen2 extends rplen by 2 bits
+* pplen2 extends pplen by 2 bits
+* mapsz indicates the size of the "remap" area. See table below for size
+* 1 bit is reserved for extensions
+
+Mapsz to Remap size is in number of 16-bit blocks:
+
+| mapsz | remap size |
+| ----- | ---------- |
+| 0 | 0 |
+| 1 | 6 |
+| 2 | 7 |
+| 3 | 8 |
+| 4 | 10 |
+| 5 | 12 |
+| 6 | 14 |
+| 7 | 16 |