From 7089a7da81166148138a60e53203b2d7da2b7899 Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Fri, 28 Jun 2019 13:42:48 +0100
Subject: [PATCH] add map functions from 8-bit to 16-bit reg and csr table
 formats

---
 riscv/sv.cc | 22 ++++++++++++++++++++++
 riscv/sv.h  | 28 ++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/riscv/sv.cc b/riscv/sv.cc
index 24a7f02..3116ebb 100644
--- a/riscv/sv.cc
+++ b/riscv/sv.cc
@@ -20,6 +20,28 @@ uint8_t maxelwidth(uint8_t wid1, uint8_t wid2)
     return std::max(wid1, wid2);
 }
 
+void sv_regmap_8to16(union sv_reg_csr_entry8 const& r8,
+                     union sv_reg_csr_entry &r16)
+{
+    r16.b.regkey  = r8.b.regkey;
+    r16.b.elwidth = r8.b.elwidth;
+    r16.b.type    = r8.b.type;
+    r16.b.regidx  = r8.b.regkey << 2; // multiply by 4, no room for 6 bits
+    r16.b.isvec   = 1;                // has to be a vector
+}
+
+void sv_predmap_8to16(union sv_pred_csr_entry8 const& r8,
+                      union sv_pred_csr_entry &r16,
+                      uint64_t table_idx)
+{
+    r16.b.regkey  = r8.b.regkey;
+    r16.b.zero    = r8.b.zero;
+    r16.b.inv     = r8.b.inv;
+    r16.b.type    = r8.b.type;
+    r16.b.regidx  = table_idx + 9; // 8-bit format starts at x9
+    r16.b.ffirst  = 0;             // no room, whoops.
+}
+
 /* increments the sub-offset appropriately in a FSM-based
    version of a twin-nested for-loop:
      for (suboffs = 0; suboffs < subvl; suboffs++) {
diff --git a/riscv/sv.h b/riscv/sv.h
index 0521df3..374335d 100644
--- a/riscv/sv.h
+++ b/riscv/sv.h
@@ -26,6 +26,19 @@ union sv_reg_csr_entry {
     unsigned short u;
 };
 
+// the 8-bit (compact) variant
+union sv_reg_csr_entry8 {
+    struct {
+        uint64_t     regkey : 5; // 5 bits
+        unsigned int elwidth: 2; // 0=dflt, 1=dflt/2, 2=dflt*2 3=8-bit
+        unsigned int type   : 1; // 1=INT, 0=FP
+    } b;
+    unsigned char u;
+};
+
+void sv_regmap_8to16(union sv_reg_csr_entry8 const& r8,
+                     union sv_reg_csr_entry8 &r16);
+
 // TODO: define separate SV CSRs for M-mode and S-Mode
 // M-Mode and S-Mode will need a minimum of 2 for int-only
 // platforms, and a minimum of 4 for int/fp.
@@ -60,6 +73,21 @@ union sv_pred_csr_entry {
     unsigned short u;
 };
 
+// the 8-bit (compact) variant
+union sv_pred_csr_entry8 {
+    struct {
+        uint64_t     regkey: 5; // 5 bits
+        unsigned int zero  : 1; // zeroing=1, skipping=0
+        unsigned int inv   : 1; // inversion=1
+        unsigned int type  : 1; // 1=INT, 0=FP
+    } b;
+    unsigned char u;
+};
+
+void sv_predmap_8to16(union sv_reg_csr_entry8 const& r8,
+                      union sv_reg_csr_entry8 &r16,
+                      uint64_t table_idx);
+
 typedef struct {
     uint64_t     regkey: 5; // 5 bits
     unsigned int zero  : 1; // zeroing=1, skipping=0
-- 
2.30.2