From 5a97139eeecac32b8127393be7fcdb23a8e98ff6 Mon Sep 17 00:00:00 2001
From: Andrew Waterman <waterman@cs.berkeley.edu>
Date: Fri, 26 Jul 2013 04:15:57 -0700
Subject: [PATCH] Rip out RVC for now

---
 riscv/decode.h                  | 38 ++++++---------------
 riscv/mmu.h                     | 59 ++++++++++-----------------------
 riscv/opcodes.h                 | 34 -------------------
 riscv/processor.cc              |  2 +-
 riscv/processor.h               | 14 --------
 rvc/README                      |  2 ++
 {riscv => rvc}/insns/c_add.h    |  0
 {riscv => rvc}/insns/c_add3.h   |  0
 {riscv => rvc}/insns/c_addi.h   |  0
 {riscv => rvc}/insns/c_addiw.h  |  0
 {riscv => rvc}/insns/c_and3.h   |  0
 {riscv => rvc}/insns/c_beq.h    |  0
 {riscv => rvc}/insns/c_bne.h    |  0
 {riscv => rvc}/insns/c_fld.h    |  0
 {riscv => rvc}/insns/c_flw.h    |  0
 {riscv => rvc}/insns/c_fsd.h    |  0
 {riscv => rvc}/insns/c_fsw.h    |  0
 {riscv => rvc}/insns/c_j.h      |  0
 {riscv => rvc}/insns/c_ld.h     |  0
 {riscv => rvc}/insns/c_ld0.h    |  0
 {riscv => rvc}/insns/c_ldsp.h   |  0
 {riscv => rvc}/insns/c_li.h     |  0
 {riscv => rvc}/insns/c_lw.h     |  0
 {riscv => rvc}/insns/c_lw0.h    |  0
 {riscv => rvc}/insns/c_lwsp.h   |  0
 {riscv => rvc}/insns/c_move.h   |  0
 {riscv => rvc}/insns/c_or3.h    |  0
 {riscv => rvc}/insns/c_sd.h     |  0
 {riscv => rvc}/insns/c_sdsp.h   |  0
 {riscv => rvc}/insns/c_slli.h   |  0
 {riscv => rvc}/insns/c_slli32.h |  0
 {riscv => rvc}/insns/c_slliw.h  |  0
 {riscv => rvc}/insns/c_srai.h   |  0
 {riscv => rvc}/insns/c_srai32.h |  0
 {riscv => rvc}/insns/c_srli.h   |  0
 {riscv => rvc}/insns/c_srli32.h |  0
 {riscv => rvc}/insns/c_sub.h    |  0
 {riscv => rvc}/insns/c_sub3.h   |  0
 {riscv => rvc}/insns/c_sw.h     |  0
 {riscv => rvc}/insns/c_swsp.h   |  0
 rvc/rvc.h                       | 30 +++++++++++++++++
 41 files changed, 61 insertions(+), 118 deletions(-)
 create mode 100644 rvc/README
 rename {riscv => rvc}/insns/c_add.h (100%)
 rename {riscv => rvc}/insns/c_add3.h (100%)
 rename {riscv => rvc}/insns/c_addi.h (100%)
 rename {riscv => rvc}/insns/c_addiw.h (100%)
 rename {riscv => rvc}/insns/c_and3.h (100%)
 rename {riscv => rvc}/insns/c_beq.h (100%)
 rename {riscv => rvc}/insns/c_bne.h (100%)
 rename {riscv => rvc}/insns/c_fld.h (100%)
 rename {riscv => rvc}/insns/c_flw.h (100%)
 rename {riscv => rvc}/insns/c_fsd.h (100%)
 rename {riscv => rvc}/insns/c_fsw.h (100%)
 rename {riscv => rvc}/insns/c_j.h (100%)
 rename {riscv => rvc}/insns/c_ld.h (100%)
 rename {riscv => rvc}/insns/c_ld0.h (100%)
 rename {riscv => rvc}/insns/c_ldsp.h (100%)
 rename {riscv => rvc}/insns/c_li.h (100%)
 rename {riscv => rvc}/insns/c_lw.h (100%)
 rename {riscv => rvc}/insns/c_lw0.h (100%)
 rename {riscv => rvc}/insns/c_lwsp.h (100%)
 rename {riscv => rvc}/insns/c_move.h (100%)
 rename {riscv => rvc}/insns/c_or3.h (100%)
 rename {riscv => rvc}/insns/c_sd.h (100%)
 rename {riscv => rvc}/insns/c_sdsp.h (100%)
 rename {riscv => rvc}/insns/c_slli.h (100%)
 rename {riscv => rvc}/insns/c_slli32.h (100%)
 rename {riscv => rvc}/insns/c_slliw.h (100%)
 rename {riscv => rvc}/insns/c_srai.h (100%)
 rename {riscv => rvc}/insns/c_srai32.h (100%)
 rename {riscv => rvc}/insns/c_srli.h (100%)
 rename {riscv => rvc}/insns/c_srli32.h (100%)
 rename {riscv => rvc}/insns/c_sub.h (100%)
 rename {riscv => rvc}/insns/c_sub3.h (100%)
 rename {riscv => rvc}/insns/c_sw.h (100%)
 rename {riscv => rvc}/insns/c_swsp.h (100%)
 create mode 100644 rvc/rvc.h

diff --git a/riscv/decode.h b/riscv/decode.h
index be7d64d..7c99581 100644
--- a/riscv/decode.h
+++ b/riscv/decode.h
@@ -223,33 +223,17 @@ private:
 #define sext_xprlen(x) (((sreg_t)(x) << (64-xprlen)) >> (64-xprlen))
 #define zext_xprlen(x) (((reg_t)(x) << (64-xprlen)) >> (64-xprlen))
 
-// RVC stuff
-
-#define INSN_IS_RVC(x) (((x) & 0x3) < 0x3)
-#define insn_length(x) (INSN_IS_RVC(x) ? 2 : 4)
-#define require_rvc if(!(sr & SR_EC)) throw_illegal_instruction
-
-#define CRD_REGNUM ((insn.bits >> 5) & 0x1f)
-#define CRD XPR.write_port(CRD_REGNUM)
-#define CRS1 XPR[(insn.bits >> 10) & 0x1f]
-#define CRS2 XPR[(insn.bits >> 5) & 0x1f]
-#define CIMM6 ((int32_t)((insn.bits >> 10) & 0x3f) << 26 >> 26)
-#define CIMM5U ((insn.bits >> 5) & 0x1f)
-#define CIMM5 ((int32_t)CIMM5U << 27 >> 27)
-#define CIMM10 ((int32_t)((insn.bits >> 5) & 0x3ff) << 22 >> 22)
-#define CBRANCH_TARGET (pc + (CIMM5 << BRANCH_ALIGN_BITS))
-#define CJUMP_TARGET (pc + (CIMM10 << JUMP_ALIGN_BITS))
-
-static const int rvc_rs1_regmap[8] = { 20, 21, 2, 3, 4, 5, 6, 7 };
-#define rvc_rd_regmap rvc_rs1_regmap
-#define rvc_rs2b_regmap rvc_rs1_regmap
-static const int rvc_rs2_regmap[8] = { 20, 21, 2, 3, 4, 5, 6, 0 };
-#define CRDS XPR.write_port(rvc_rd_regmap[(insn.bits >> 13) & 0x7])
-#define FCRDS FPR.write_port(rvc_rd_regmap[(insn.bits >> 13) & 0x7])
-#define CRS1S XPR[rvc_rs1_regmap[(insn.bits >> 10) & 0x7]]
-#define CRS2S XPR[rvc_rs2_regmap[(insn.bits >> 13) & 0x7]]
-#define CRS2BS XPR[rvc_rs2b_regmap[(insn.bits >> 5) & 0x7]]
-#define FCRS2S FPR[rvc_rs2_regmap[(insn.bits >> 13) & 0x7]]
+#define insn_length(x) \
+  (((x) & 0x03) < 0x03 ? 2 : \
+   ((x) & 0x1f) < 0x1f ? 4 : \
+   ((x) & 0x3f) < 0x3f ? 6 : \
+   8)
+
+#define set_pc(x) \
+  do { if ((x) & 3 /* For now... */) \
+         throw trap_instruction_address_misaligned; \
+       npc = (x); \
+     } while(0)
 
 // vector stuff
 #define VL vl
diff --git a/riscv/mmu.h b/riscv/mmu.h
index 9e1218c..49a5f0b 100644
--- a/riscv/mmu.h
+++ b/riscv/mmu.h
@@ -102,54 +102,30 @@ public:
   };
 
   // load instruction from memory at aligned address.
-  // (needed because instruction alignment requirement is variable
-  // if RVC is supported)
-  // returns the instruction at the specified address, given the current
-  // RVC mode.  func is set to a pointer to a function that knows how to
-  // execute the returned instruction.
-  inline insn_fetch_t load_insn(reg_t addr, bool rvc)
+  inline insn_fetch_t load_insn(reg_t addr)
   {
-    #ifdef RISCV_ENABLE_RVC
-    if(addr % 4 == 2 && rvc) // fetch across word boundary
+#ifdef RISCV_ENABLE_RVC
+# error TODO: Make MMU instruction cache support 2-byte alignment
+#endif
+    reg_t idx = (addr/sizeof(insn_t::itype)) % ICACHE_ENTRIES;
+    if (unlikely(icache_tag[idx] != addr))
     {
-      reg_t addr_lo = translate(addr, 2, false, true);
+      reg_t paddr = translate(addr, sizeof(insn_t::itype), false, true);
       insn_fetch_t fetch;
-      fetch.insn.bits = *(uint16_t*)(mem + addr_lo);
+      fetch.insn.itype = *(decltype(insn_t::itype)*)(mem + paddr);
       fetch.func = proc->decode_insn(fetch.insn);
 
-      if(!INSN_IS_RVC(fetch.insn.bits))
-      {
-        reg_t addr_hi = translate(addr+2, 2, false, true);
-        fetch.insn.bits |= (uint32_t)*(uint16_t*)(mem + addr_hi) << 16;
-      }
-      return fetch;
-    }
-    else
-    #endif
-    {
-      reg_t idx = (addr/sizeof(insn_t::itype)) % ICACHE_ENTRIES;
-      insn_fetch_t fetch;
-      if (unlikely(icache_tag[idx] != addr))
+      reg_t idx = (paddr/sizeof(insn_t::itype)) % ICACHE_ENTRIES;
+      icache_tag[idx] = addr;
+      icache_data[idx] = fetch;
+
+      if (tracer.interested_in_range(paddr, paddr + sizeof(insn_t::itype), false, true))
       {
-        reg_t paddr = translate(addr, sizeof(insn_t::itype), false, true);
-        fetch.insn.itype = *(decltype(insn_t::itype)*)(mem + paddr);
-        fetch.func = proc->decode_insn(fetch.insn);
-
-        reg_t idx = (paddr/sizeof(insn_t::itype)) % ICACHE_ENTRIES;
-        icache_tag[idx] = addr;
-        icache_data[idx] = fetch.insn;
-        icache_func[idx] = fetch.func;
-
-        if (tracer.interested_in_range(paddr, paddr + sizeof(insn_t::itype), false, true))
-        {
-          icache_tag[idx] = -1;
-          tracer.trace(paddr, sizeof(insn_t::itype), false, true);
-        }
+        icache_tag[idx] = -1;
+        tracer.trace(paddr, sizeof(insn_t::itype), false, true);
       }
-      fetch.insn = icache_data[idx];
-      fetch.func = icache_func[idx];
-      return fetch;
     }
+    return icache_data[idx];
   }
 
   reg_t get_badvaddr() { return badvaddr; }
@@ -174,8 +150,7 @@ private:
 
   // implement an instruction cache for simulator performance
   static const reg_t ICACHE_ENTRIES = 256;
-  insn_t icache_data[ICACHE_ENTRIES];
-  insn_func_t icache_func[ICACHE_ENTRIES];
+  insn_fetch_t icache_data[ICACHE_ENTRIES];
 
   // implement a TLB for simulator performance
   static const reg_t TLB_ENTRIES = 256;
diff --git a/riscv/opcodes.h b/riscv/opcodes.h
index aaf8e67..f18aebd 100644
--- a/riscv/opcodes.h
+++ b/riscv/opcodes.h
@@ -8,10 +8,7 @@ DECLARE_INSN(bltu, 0x363, 0x3ff)
 DECLARE_INSN(vlsegstwu, 0xb0b, 0xfff)
 DECLARE_INSN(vvcfg, 0x473, 0xf801ffff)
 DECLARE_INSN(movz, 0x2f7, 0x1ffff)
-DECLARE_INSN(c_ld, 0x9, 0x1f)
-DECLARE_INSN(c_srli32, 0xc19, 0x1c1f)
 DECLARE_INSN(fmin_s, 0x18053, 0x1ffff)
-DECLARE_INSN(c_lw0, 0x12, 0x801f)
 DECLARE_INSN(slliw, 0x9b, 0x3f83ff)
 DECLARE_INSN(lb, 0x3, 0x3ff)
 DECLARE_INSN(vlwu, 0x30b, 0x3fffff)
@@ -23,7 +20,6 @@ DECLARE_INSN(lw, 0x103, 0x3ff)
 DECLARE_INSN(add, 0x33, 0x1ffff)
 DECLARE_INSN(fcvt_d_s, 0x100d3, 0x3ff1ff)
 DECLARE_INSN(mfpcr, 0x17b, 0x3fffff)
-DECLARE_INSN(c_fsd, 0x18, 0x1f)
 DECLARE_INSN(fmax_d, 0x190d3, 0x1ffff)
 DECLARE_INSN(bne, 0xe3, 0x3ff)
 DECLARE_INSN(rdcycle, 0x277, 0x7ffffff)
@@ -31,30 +27,22 @@ DECLARE_INSN(fcvt_s_d, 0x11053, 0x3ff1ff)
 DECLARE_INSN(vlh, 0x8b, 0x3fffff)
 DECLARE_INSN(bgeu, 0x3e3, 0x3ff)
 DECLARE_INSN(vflstd, 0x158b, 0x1ffff)
-DECLARE_INSN(c_li, 0x0, 0x1f)
 DECLARE_INSN(fadd_d, 0xd3, 0x1f1ff)
 DECLARE_INSN(sltiu, 0x193, 0x3ff)
 DECLARE_INSN(mtpcr, 0x1fb, 0x1ffff)
 DECLARE_INSN(vlb, 0xb, 0x3fffff)
 DECLARE_INSN(stop, 0x177, 0xffffffff)
 DECLARE_INSN(vld, 0x18b, 0x3fffff)
-DECLARE_INSN(c_slli, 0x19, 0x1c1f)
 DECLARE_INSN(break, 0xf7, 0xffffffff)
 DECLARE_INSN(fcvt_s_w, 0xe053, 0x3ff1ff)
 DECLARE_INSN(vflstw, 0x150b, 0x1ffff)
 DECLARE_INSN(mul, 0x433, 0x1ffff)
-DECLARE_INSN(c_lw, 0xa, 0x1f)
 DECLARE_INSN(vxcptevac, 0x237b, 0xf83fffff)
 DECLARE_INSN(vlw, 0x10b, 0x3fffff)
 DECLARE_INSN(vssegstw, 0x90f, 0xfff)
 DECLARE_INSN(amominu_d, 0x19ab, 0x1ffff)
-DECLARE_INSN(c_sdsp, 0x6, 0x1f)
 DECLARE_INSN(mftx_d, 0x1c0d3, 0x3fffff)
 DECLARE_INSN(srli, 0x293, 0x3f03ff)
-DECLARE_INSN(c_srli, 0x819, 0x1c1f)
-DECLARE_INSN(c_ldsp, 0x4, 0x1f)
-DECLARE_INSN(c_flw, 0x14, 0x1f)
-DECLARE_INSN(c_srai32, 0x1419, 0x1c1f)
 DECLARE_INSN(amominu_w, 0x192b, 0x1ffff)
 DECLARE_INSN(divuw, 0x6bb, 0x1ffff)
 DECLARE_INSN(mulw, 0x43b, 0x1ffff)
@@ -118,10 +106,8 @@ DECLARE_INSN(amoand_w, 0x92b, 0x1ffff)
 DECLARE_INSN(feq_s, 0x15053, 0x1ffff)
 DECLARE_INSN(fsgnjx_d, 0x70d3, 0x1ffff)
 DECLARE_INSN(sra, 0x102b3, 0x1ffff)
-DECLARE_INSN(c_lwsp, 0x5, 0x1f)
 DECLARE_INSN(bge, 0x2e3, 0x3ff)
 DECLARE_INSN(venqimm2, 0x337b, 0xf801ffff)
-DECLARE_INSN(c_add3, 0x1c, 0x31f)
 DECLARE_INSN(sraiw, 0x1029b, 0x3f83ff)
 DECLARE_INSN(vssegd, 0x218f, 0x1ffff)
 DECLARE_INSN(srl, 0x2b3, 0x1ffff)
@@ -139,11 +125,8 @@ DECLARE_INSN(or, 0x333, 0x1ffff)
 DECLARE_INSN(rdinstret, 0xa77, 0x7ffffff)
 DECLARE_INSN(fcvt_wu_d, 0xb0d3, 0x3ff1ff)
 DECLARE_INSN(subw, 0x1003b, 0x1ffff)
-DECLARE_INSN(c_swsp, 0x8, 0x1f)
 DECLARE_INSN(fmax_s, 0x19053, 0x1ffff)
 DECLARE_INSN(amomaxu_d, 0x1dab, 0x1ffff)
-DECLARE_INSN(c_slliw, 0x1819, 0x1c1f)
-DECLARE_INSN(c_fld, 0x15, 0x1f)
 DECLARE_INSN(vlstw, 0x110b, 0x1ffff)
 DECLARE_INSN(vlsth, 0x108b, 0x1ffff)
 DECLARE_INSN(xori, 0x213, 0x3ff)
@@ -152,7 +135,6 @@ DECLARE_INSN(amomaxu_w, 0x1d2b, 0x1ffff)
 DECLARE_INSN(fcvt_wu_s, 0xb053, 0x3ff1ff)
 DECLARE_INSN(vlstb, 0x100b, 0x1ffff)
 DECLARE_INSN(vlstd, 0x118b, 0x1ffff)
-DECLARE_INSN(c_ld0, 0x8012, 0x801f)
 DECLARE_INSN(rdtime, 0x677, 0x7ffffff)
 DECLARE_INSN(andi, 0x393, 0x3ff)
 DECLARE_INSN(clearpcr, 0x7b, 0x3ff)
@@ -162,26 +144,19 @@ DECLARE_INSN(fnmadd_s, 0x4f, 0x1ff)
 DECLARE_INSN(jal, 0x6f, 0x7f)
 DECLARE_INSN(lwu, 0x303, 0x3ff)
 DECLARE_INSN(vlsegstbu, 0xa0b, 0xfff)
-DECLARE_INSN(c_beq, 0x10, 0x1f)
 DECLARE_INSN(vlhu, 0x28b, 0x3fffff)
 DECLARE_INSN(vfsstd, 0x158f, 0x1ffff)
 DECLARE_INSN(fnmadd_d, 0xcf, 0x1ff)
 DECLARE_INSN(amoadd_d, 0x1ab, 0x1ffff)
-DECLARE_INSN(c_sw, 0xd, 0x1f)
 DECLARE_INSN(lr_d, 0x101ab, 0x3fffff)
-DECLARE_INSN(c_move, 0x2, 0x801f)
 DECLARE_INSN(fcvt_w_s, 0xa053, 0x3ff1ff)
-DECLARE_INSN(c_fsw, 0x16, 0x1f)
-DECLARE_INSN(c_j, 0x8002, 0x801f)
 DECLARE_INSN(mulhsu, 0x533, 0x1ffff)
-DECLARE_INSN(c_sd, 0xc, 0x1f)
 DECLARE_INSN(amoadd_w, 0x12b, 0x1ffff)
 DECLARE_INSN(fcvt_d_lu, 0xd0d3, 0x3ff1ff)
 DECLARE_INSN(amomax_d, 0x15ab, 0x1ffff)
 DECLARE_INSN(fsd, 0x1a7, 0x3ff)
 DECLARE_INSN(fcvt_w_d, 0xa0d3, 0x3ff1ff)
 DECLARE_INSN(fmovz, 0xaf7, 0x1ffff)
-DECLARE_INSN(c_or3, 0x21c, 0x31f)
 DECLARE_INSN(vmvv, 0x73, 0x3fffff)
 DECLARE_INSN(vfssegstw, 0xd0f, 0xfff)
 DECLARE_INSN(slt, 0x133, 0x1ffff)
@@ -194,7 +169,6 @@ DECLARE_INSN(flw, 0x107, 0x3ff)
 DECLARE_INSN(remw, 0x73b, 0x1ffff)
 DECLARE_INSN(sltu, 0x1b3, 0x1ffff)
 DECLARE_INSN(slli, 0x93, 0x3f03ff)
-DECLARE_INSN(c_and3, 0x31c, 0x31f)
 DECLARE_INSN(vssegw, 0x210f, 0x1ffff)
 DECLARE_INSN(amoor_w, 0xd2b, 0x1ffff)
 DECLARE_INSN(vsd, 0x18f, 0x3fffff)
@@ -209,10 +183,8 @@ DECLARE_INSN(vf, 0x3f3, 0xf80003ff)
 DECLARE_INSN(vlsegstw, 0x90b, 0xfff)
 DECLARE_INSN(syscall, 0x77, 0xffffffff)
 DECLARE_INSN(fsgnj_s, 0x5053, 0x1ffff)
-DECLARE_INSN(c_addi, 0x1, 0x1f)
 DECLARE_INSN(vfmvv, 0x173, 0x3fffff)
 DECLARE_INSN(vlstwu, 0x130b, 0x1ffff)
-DECLARE_INSN(c_sub3, 0x11c, 0x31f)
 DECLARE_INSN(vsh, 0x8f, 0x3fffff)
 DECLARE_INSN(vlsegstb, 0x80b, 0xfff)
 DECLARE_INSN(vxcptsave, 0x37b, 0xf83fffff)
@@ -223,7 +195,6 @@ DECLARE_INSN(vlsegsth, 0x88b, 0xfff)
 DECLARE_INSN(amomax_w, 0x152b, 0x1ffff)
 DECLARE_INSN(fsgnj_d, 0x50d3, 0x1ffff)
 DECLARE_INSN(vflsegstw, 0xd0b, 0xfff)
-DECLARE_INSN(c_sub, 0x801a, 0x801f)
 DECLARE_INSN(mulhu, 0x5b3, 0x1ffff)
 DECLARE_INSN(fence_v_g, 0x2af, 0x3ff)
 DECLARE_INSN(vmsv, 0x873, 0x3fffff)
@@ -234,7 +205,6 @@ DECLARE_INSN(vxcpthold, 0x277b, 0xffffffff)
 DECLARE_INSN(fcvt_s_l, 0xc053, 0x3ff1ff)
 DECLARE_INSN(vflsegstd, 0xd8b, 0xfff)
 DECLARE_INSN(auipc, 0x17, 0x7f)
-DECLARE_INSN(c_add, 0x1a, 0x801f)
 DECLARE_INSN(fcvt_lu_d, 0x90d3, 0x3ff1ff)
 DECLARE_INSN(vfld, 0x58b, 0x3fffff)
 DECLARE_INSN(sc_d, 0x105ab, 0x1ffff)
@@ -243,16 +213,13 @@ DECLARE_INSN(fmovn, 0xef7, 0x1ffff)
 DECLARE_INSN(vssegh, 0x208f, 0x1ffff)
 DECLARE_INSN(fsqrt_s, 0x4053, 0x3ff1ff)
 DECLARE_INSN(vxcptkill, 0xb7b, 0xffffffff)
-DECLARE_INSN(c_srai, 0x1019, 0x1c1f)
 DECLARE_INSN(amomin_w, 0x112b, 0x1ffff)
 DECLARE_INSN(fsgnjn_s, 0x6053, 0x1ffff)
-DECLARE_INSN(c_slli32, 0x419, 0x1c1f)
 DECLARE_INSN(vlsegwu, 0x230b, 0x1ffff)
 DECLARE_INSN(vfsw, 0x50f, 0x3fffff)
 DECLARE_INSN(amoswap_d, 0x5ab, 0x1ffff)
 DECLARE_INSN(fsqrt_d, 0x40d3, 0x3ff1ff)
 DECLARE_INSN(vflw, 0x50b, 0x3fffff)
-DECLARE_INSN(c_bne, 0x11, 0x1f)
 DECLARE_INSN(fmadd_d, 0xc3, 0x1ff)
 DECLARE_INSN(divw, 0x63b, 0x1ffff)
 DECLARE_INSN(amomin_d, 0x11ab, 0x1ffff)
@@ -268,7 +235,6 @@ DECLARE_INSN(vlsegh, 0x208b, 0x1ffff)
 DECLARE_INSN(sw, 0x123, 0x3ff)
 DECLARE_INSN(fmsub_s, 0x47, 0x1ff)
 DECLARE_INSN(vfssegw, 0x250f, 0x1ffff)
-DECLARE_INSN(c_addiw, 0x1d, 0x1f)
 DECLARE_INSN(lhu, 0x283, 0x3ff)
 DECLARE_INSN(sh, 0xa3, 0x3ff)
 DECLARE_INSN(vlsegw, 0x210b, 0x1ffff)
diff --git a/riscv/processor.cc b/riscv/processor.cc
index 5d82937..3bd4a19 100644
--- a/riscv/processor.cc
+++ b/riscv/processor.cc
@@ -132,7 +132,7 @@ void processor_t::step(size_t n, bool noisy)
     // execute_insn fetches and executes one instruction
     #define execute_insn(noisy) \
       do { \
-        mmu_t::insn_fetch_t fetch = _mmu.load_insn(npc, sr & SR_EC); \
+        mmu_t::insn_fetch_t fetch = _mmu.load_insn(npc); \
         if(noisy) disasm(fetch.insn, npc); \
         npc = fetch.func(this, fetch.insn, npc); \
         pc = npc; \
diff --git a/riscv/processor.h b/riscv/processor.h
index c2d0ea5..08c3672 100644
--- a/riscv/processor.h
+++ b/riscv/processor.h
@@ -109,18 +109,4 @@ private:
   reg_t illegal_instruction(insn_t insn, reg_t pc);
 };
 
-#ifndef RISCV_ENABLE_RVC
-# define set_pc(x) \
-  do { if ((x) & 3) \
-         throw trap_instruction_address_misaligned; \
-       npc = (x); \
-     } while(0)
-#else
-# define set_pc(x) \
-  do { if ((x) & ((sr & SR_EC) ? 1 : 3)) \
-         throw trap_instruction_address_misaligned; \
-       npc = (x); \
-     } while(0)
-#endif
-
 #endif
diff --git a/rvc/README b/rvc/README
new file mode 100644
index 0000000..feabcd3
--- /dev/null
+++ b/rvc/README
@@ -0,0 +1,2 @@
+This directory contains work in progress on RISC-V Compressed (RVC), a 16-bit
+instruction encoding for reduced code size.  It is not currently usable.
diff --git a/riscv/insns/c_add.h b/rvc/insns/c_add.h
similarity index 100%
rename from riscv/insns/c_add.h
rename to rvc/insns/c_add.h
diff --git a/riscv/insns/c_add3.h b/rvc/insns/c_add3.h
similarity index 100%
rename from riscv/insns/c_add3.h
rename to rvc/insns/c_add3.h
diff --git a/riscv/insns/c_addi.h b/rvc/insns/c_addi.h
similarity index 100%
rename from riscv/insns/c_addi.h
rename to rvc/insns/c_addi.h
diff --git a/riscv/insns/c_addiw.h b/rvc/insns/c_addiw.h
similarity index 100%
rename from riscv/insns/c_addiw.h
rename to rvc/insns/c_addiw.h
diff --git a/riscv/insns/c_and3.h b/rvc/insns/c_and3.h
similarity index 100%
rename from riscv/insns/c_and3.h
rename to rvc/insns/c_and3.h
diff --git a/riscv/insns/c_beq.h b/rvc/insns/c_beq.h
similarity index 100%
rename from riscv/insns/c_beq.h
rename to rvc/insns/c_beq.h
diff --git a/riscv/insns/c_bne.h b/rvc/insns/c_bne.h
similarity index 100%
rename from riscv/insns/c_bne.h
rename to rvc/insns/c_bne.h
diff --git a/riscv/insns/c_fld.h b/rvc/insns/c_fld.h
similarity index 100%
rename from riscv/insns/c_fld.h
rename to rvc/insns/c_fld.h
diff --git a/riscv/insns/c_flw.h b/rvc/insns/c_flw.h
similarity index 100%
rename from riscv/insns/c_flw.h
rename to rvc/insns/c_flw.h
diff --git a/riscv/insns/c_fsd.h b/rvc/insns/c_fsd.h
similarity index 100%
rename from riscv/insns/c_fsd.h
rename to rvc/insns/c_fsd.h
diff --git a/riscv/insns/c_fsw.h b/rvc/insns/c_fsw.h
similarity index 100%
rename from riscv/insns/c_fsw.h
rename to rvc/insns/c_fsw.h
diff --git a/riscv/insns/c_j.h b/rvc/insns/c_j.h
similarity index 100%
rename from riscv/insns/c_j.h
rename to rvc/insns/c_j.h
diff --git a/riscv/insns/c_ld.h b/rvc/insns/c_ld.h
similarity index 100%
rename from riscv/insns/c_ld.h
rename to rvc/insns/c_ld.h
diff --git a/riscv/insns/c_ld0.h b/rvc/insns/c_ld0.h
similarity index 100%
rename from riscv/insns/c_ld0.h
rename to rvc/insns/c_ld0.h
diff --git a/riscv/insns/c_ldsp.h b/rvc/insns/c_ldsp.h
similarity index 100%
rename from riscv/insns/c_ldsp.h
rename to rvc/insns/c_ldsp.h
diff --git a/riscv/insns/c_li.h b/rvc/insns/c_li.h
similarity index 100%
rename from riscv/insns/c_li.h
rename to rvc/insns/c_li.h
diff --git a/riscv/insns/c_lw.h b/rvc/insns/c_lw.h
similarity index 100%
rename from riscv/insns/c_lw.h
rename to rvc/insns/c_lw.h
diff --git a/riscv/insns/c_lw0.h b/rvc/insns/c_lw0.h
similarity index 100%
rename from riscv/insns/c_lw0.h
rename to rvc/insns/c_lw0.h
diff --git a/riscv/insns/c_lwsp.h b/rvc/insns/c_lwsp.h
similarity index 100%
rename from riscv/insns/c_lwsp.h
rename to rvc/insns/c_lwsp.h
diff --git a/riscv/insns/c_move.h b/rvc/insns/c_move.h
similarity index 100%
rename from riscv/insns/c_move.h
rename to rvc/insns/c_move.h
diff --git a/riscv/insns/c_or3.h b/rvc/insns/c_or3.h
similarity index 100%
rename from riscv/insns/c_or3.h
rename to rvc/insns/c_or3.h
diff --git a/riscv/insns/c_sd.h b/rvc/insns/c_sd.h
similarity index 100%
rename from riscv/insns/c_sd.h
rename to rvc/insns/c_sd.h
diff --git a/riscv/insns/c_sdsp.h b/rvc/insns/c_sdsp.h
similarity index 100%
rename from riscv/insns/c_sdsp.h
rename to rvc/insns/c_sdsp.h
diff --git a/riscv/insns/c_slli.h b/rvc/insns/c_slli.h
similarity index 100%
rename from riscv/insns/c_slli.h
rename to rvc/insns/c_slli.h
diff --git a/riscv/insns/c_slli32.h b/rvc/insns/c_slli32.h
similarity index 100%
rename from riscv/insns/c_slli32.h
rename to rvc/insns/c_slli32.h
diff --git a/riscv/insns/c_slliw.h b/rvc/insns/c_slliw.h
similarity index 100%
rename from riscv/insns/c_slliw.h
rename to rvc/insns/c_slliw.h
diff --git a/riscv/insns/c_srai.h b/rvc/insns/c_srai.h
similarity index 100%
rename from riscv/insns/c_srai.h
rename to rvc/insns/c_srai.h
diff --git a/riscv/insns/c_srai32.h b/rvc/insns/c_srai32.h
similarity index 100%
rename from riscv/insns/c_srai32.h
rename to rvc/insns/c_srai32.h
diff --git a/riscv/insns/c_srli.h b/rvc/insns/c_srli.h
similarity index 100%
rename from riscv/insns/c_srli.h
rename to rvc/insns/c_srli.h
diff --git a/riscv/insns/c_srli32.h b/rvc/insns/c_srli32.h
similarity index 100%
rename from riscv/insns/c_srli32.h
rename to rvc/insns/c_srli32.h
diff --git a/riscv/insns/c_sub.h b/rvc/insns/c_sub.h
similarity index 100%
rename from riscv/insns/c_sub.h
rename to rvc/insns/c_sub.h
diff --git a/riscv/insns/c_sub3.h b/rvc/insns/c_sub3.h
similarity index 100%
rename from riscv/insns/c_sub3.h
rename to rvc/insns/c_sub3.h
diff --git a/riscv/insns/c_sw.h b/rvc/insns/c_sw.h
similarity index 100%
rename from riscv/insns/c_sw.h
rename to rvc/insns/c_sw.h
diff --git a/riscv/insns/c_swsp.h b/rvc/insns/c_swsp.h
similarity index 100%
rename from riscv/insns/c_swsp.h
rename to rvc/insns/c_swsp.h
diff --git a/rvc/rvc.h b/rvc/rvc.h
new file mode 100644
index 0000000..997ffc6
--- /dev/null
+++ b/rvc/rvc.h
@@ -0,0 +1,30 @@
+#ifndef _RVC_H
+#define _RVC_H
+
+#define INSN_IS_RVC(x) (((x) & 0x3) < 0x3)
+#define insn_length(x) (INSN_IS_RVC(x) ? 2 : 4)
+#define require_rvc if(!(sr & SR_EC)) throw_illegal_instruction
+
+#define CRD_REGNUM ((insn.bits >> 5) & 0x1f)
+#define CRD XPR.write_port(CRD_REGNUM)
+#define CRS1 XPR[(insn.bits >> 10) & 0x1f]
+#define CRS2 XPR[(insn.bits >> 5) & 0x1f]
+#define CIMM6 ((int32_t)((insn.bits >> 10) & 0x3f) << 26 >> 26)
+#define CIMM5U ((insn.bits >> 5) & 0x1f)
+#define CIMM5 ((int32_t)CIMM5U << 27 >> 27)
+#define CIMM10 ((int32_t)((insn.bits >> 5) & 0x3ff) << 22 >> 22)
+#define CBRANCH_TARGET (pc + (CIMM5 << BRANCH_ALIGN_BITS))
+#define CJUMP_TARGET (pc + (CIMM10 << JUMP_ALIGN_BITS))
+
+static const int rvc_rs1_regmap[8] = { 20, 21, 2, 3, 4, 5, 6, 7 };
+#define rvc_rd_regmap rvc_rs1_regmap
+#define rvc_rs2b_regmap rvc_rs1_regmap
+static const int rvc_rs2_regmap[8] = { 20, 21, 2, 3, 4, 5, 6, 0 };
+#define CRDS XPR.write_port(rvc_rd_regmap[(insn.bits >> 13) & 0x7])
+#define FCRDS FPR.write_port(rvc_rd_regmap[(insn.bits >> 13) & 0x7])
+#define CRS1S XPR[rvc_rs1_regmap[(insn.bits >> 10) & 0x7]]
+#define CRS2S XPR[rvc_rs2_regmap[(insn.bits >> 13) & 0x7]]
+#define CRS2BS XPR[rvc_rs2b_regmap[(insn.bits >> 5) & 0x7]]
+#define FCRS2S FPR[rvc_rs2_regmap[(insn.bits >> 13) & 0x7]]
+
+#endif
-- 
2.30.2