From 34c8b6cf3dfce631e2f002901364fe5ad6db0c59 Mon Sep 17 00:00:00 2001
From: Donald Sebastian Leung <dl@m-labs.hk>
Date: Thu, 30 Jul 2020 12:45:32 +0800
Subject: [PATCH] Create U-type instruction format

---
 insns/insn_U_type.py  | 33 +++++++++++++++++++++++++++++++++
 insns/insn_general.py |  2 +-
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 insns/insn_U_type.py

diff --git a/insns/insn_U_type.py b/insns/insn_U_type.py
new file mode 100644
index 0000000..334d15c
--- /dev/null
+++ b/insns/insn_U_type.py
@@ -0,0 +1,33 @@
+from insn_general import *
+
+class rvfi_insn_U_type(rvfi_insn_general):
+    def __init__(self, RISCV_FORMAL_ILEN=32, RISCV_FORMAL_XLEN=32):
+        super(rvfi_insn_U_type, self).__init__(RISCV_FORMAL_ILEN, RISCV_FORMAL_XLEN)
+        self.insn_padding = Signal(self.RISCV_FORMAL_ILEN)
+        self.insn_imm = Signal(self.RISCV_FORMAL_XLEN)
+        self.insn_rd = Signal(5)
+        self.insn_opcode = Signal(7)
+        self.misa_ok = Signal(1)
+    def ports(self):
+        return super(rvfi_insn_U_type, self).ports()
+    def elaborate(self, platform):
+        m = super(rvfi_insn_U_type, self).elaborate(platform)
+
+        # U-type instruction format
+        m.d.comb += self.insn_padding.eq(self.rvfi_insn >> 32)
+        m.d.comb += self.insn_imm.eq(Value.as_signed(self.rvfi_insn[12:32] << 12))
+        m.d.comb += self.insn_rd.eq(self.rvfi_insn[7:12])
+        m.d.comb += self.insn_opcode.eq(self.rvfi_insn[:7])
+
+        m.d.comb += self.misa_ok.eq(1)
+
+        # default assignments
+        m.d.comb += self.spec_rs1_addr.eq(0)
+        m.d.comb += self.spec_rs2_addr.eq(0)
+        m.d.comb += self.spec_trap.eq(~self.misa_ok)
+        m.d.comb += self.spec_mem_addr.eq(0)
+        m.d.comb += self.spec_mem_rmask.eq(0)
+        m.d.comb += self.spec_mem_wmask.eq(0)
+        m.d.comb += self.spec_mem_wdata.eq(0)
+
+        return m
diff --git a/insns/insn_general.py b/insns/insn_general.py
index 41186ba..c649196 100644
--- a/insns/insn_general.py
+++ b/insns/insn_general.py
@@ -1,6 +1,6 @@
 from nmigen import *
 
-class rvfi_insn_generic(Elaboratable):
+class rvfi_insn_general(Elaboratable):
     def __init__(self, RISCV_FORMAL_ILEN=32, RISCV_FORMAL_XLEN=32):
         self.RISCV_FORMAL_ILEN = RISCV_FORMAL_ILEN
         self.RISCV_FORMAL_XLEN = RISCV_FORMAL_XLEN