From 53b90e44e278dc5f624a24a92ebe1f145dbd6a61 Mon Sep 17 00:00:00 2001 From: lkcl Date: Sun, 30 Jun 2019 11:34:01 +0100 Subject: [PATCH] --- .../sv_prefix_proposal/discussion.rst | 53 ++++++++----------- 1 file changed, 22 insertions(+), 31 deletions(-) diff --git a/simple_v_extension/sv_prefix_proposal/discussion.rst b/simple_v_extension/sv_prefix_proposal/discussion.rst index 3aca9d894..0bbb5f8a2 100644 --- a/simple_v_extension/sv_prefix_proposal/discussion.rst +++ b/simple_v_extension/sv_prefix_proposal/discussion.rst @@ -34,21 +34,12 @@ Or, just "to hell with it" and just take the entire opcode and stuff C into it, |funct3 | jump target | op | CJ | +----------+--------------------------------------------------+-------+--------+ -* 16 bits RVC to go into RV128 "MAJOR OPCODE 2" and "MAJOR OPCODE 3". - RVC op[1:0], bit[1] selects OPCODE-2 or OPCODE-3, therefore - 17 bits remain in the 32-bit opcode space -* 32-bit opcode prefix takes 7 bits, therefore 10 bits remain to fit +* top 14 bits of RVC to go into "MAJOR OPCODE 0-2" to represent + RVC op[1:0] == 0b00, 0b01 and 0b02. Therefore, + 18 bits remain in the 32-bit opcode space +* 32-bit opcode prefix takes 7 bits, therefore 11 bits remain to fit a SVPrefix. -* compared to P48, 11 bits are needed. -* however, with the exception of LD/ST (and C.MV) these all provide *three* - operands: rs1, rs2 and rs3. -* therefore, 1 field can go, and that just leaves what to do with LD/ST - and C.MV -* should twin-predication be sacrificed? -* should one of the vectorisation modes be sacrificed? -* is there room in ohe of the other "MAJOR CUSTOM OPCODEs" (0,1) to - fit the "other" mode somehow? -* can one of the vew bits be sacrificed instead, reducing vitp7 by 1 bit? +* compared to P48, 11 bits are needed, and we have a match. P48: @@ -74,23 +65,23 @@ P48: P32C: -+---------------+--------+--------+----------+--------+-------------+------+--------+--------+ -| Encoding | 17 | 16 | 15 | 13 | 12 | 11:7 | 6 | 5:0 | -+---------------+--------+--------+----------+--------+-------------+------+--------+--------+ -| P32C-CL-type | rd[5] | rs1[5] | vitp7[6] | vs1 | vitp7[5:0] | *Rsvd* | 011111 | -+---------------+--------+--------+----------+--------+--------------------+--------+--------+ -| P32C-CS-type |vitp7[6]| rs1[5] | rs2[5] | vs1 | vitp7[5:0] | *Rsvd* | 011111 | -+---------------+--------+--------+----------+--------+-------------+------+--------+--------+ -| P32C-FR-type | rd[5] | rs1[5] | rs2[5] | vs1 | *Rsvd* | vtp5 | *Rsvd* | 011111 | -+---------------+--------+--------+----------+--------+-------------+------+--------+--------+ -| P32C-FR-type | rd[5] | rs1[5] | rs2[5] | vs1 | *Rsvd* | vtp5 | *Rsvd* | 011111 | -+---------------+--------+--------+----------+--------+-------------+------+--------+--------+ -| P32C-CR-type | rd[5] | rs1[5] | rs2[5] | vs1 | vitp6 | *Rsvd* | 011111 | -+---------------+--------+--------+----------+--------+--------------------+--------+--------+ -| P32C-CA-type | rd[5] | rs1[5] | vitp7[6] | vs1 | vitp7[5:0] | *Rsvd* | 011111 | -+---------------+--------+--------+----------+--------+--------------------+--------+--------+ -| P32C-CU-type | rd[5] | *Rsvd* | *Rsvd* | *Rsvd* | vitp6 | *Rsvd* | 011111 | -+---------------+--------+--------+----------+--------+--------------------+--------+--------+ +P48: + ++---------------+--------+--------+----------+-----+--------+-------------+------+--------+--------+ +| Encoding | 17 | 16 | 15 | 14 | 13 | 12 | 11:7 | 6 | 5:0 | ++---------------+--------+--------+----------+-----+--------+-------------+------+--------+--------+ +| P32C-CL-type | rd[5] | rs1[5] | vitp7[6] | vd | vs1 | vitp7[5:0] | *Rsvd* | 011111 | ++---------------+--------+--------+----------+-----+--------+--------------------+--------+--------+ +| P32C-CS-type |vitp7[6]| rs1[5] | rs2[5] | vs2 | vs1 | vitp7[5:0] | *Rsvd* | 011111 | ++---------------+--------+--------+----------+-----+--------+--------------------+--------+--------+ +| P32C-CR-type | rd[5] | rs1[5] | *Rsvd* | vd | vs1 | vitp6 | *Rsvd* | 011111 | ++---------------+--------+--------+----------+-----+--------+--------------------+--------+--------+ +| P32C-CI1-type | rd[5] | rs1[5] | vitp7[6] | vd | vs1 | vitp7[5:0] | *Rsvd* | 011111 | ++---------------+--------+--------+----------+-----+--------+--------------------+--------+--------+ +| P32C-CI2-type | rd[5] | *Rsvd* | *Rsvd* | vd | *Rsvd* | vitp6 | *Rsvd* | 011111 | ++---------------+--------+--------+----------+-----+--------+--------------------+--------+--------+ +| P32C-CMv-type | rd[5] | rs1[5] | vitp7[6] | vd | vs1 | vitp7[5:0] | *Rsvd* | 011111 | ++---------------+--------+--------+----------+-----+--------+--------------------+--------+--------+ Questions ========= -- 2.30.2