From f95a85de0082010e4af83e26e99299d601bb48d6 Mon Sep 17 00:00:00 2001
From: Steven Le Rouzic <steven.lerouzic@gmail.com>
Date: Mon, 13 May 2024 00:04:44 +0200
Subject: Some work on CSR

---
 emulator/instruction.h | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 emulator/instruction.h

(limited to 'emulator/instruction.h')

diff --git a/emulator/instruction.h b/emulator/instruction.h
new file mode 100644
index 0000000..97c9fe9
--- /dev/null
+++ b/emulator/instruction.h
@@ -0,0 +1,80 @@
+#pragma once
+
+#include <stdint.h>
+
+#include "emulator/bits.h"
+
+struct Instruction
+{
+    uint8_t  opcode;
+    uint8_t  rs1;
+    uint8_t  rs2;
+    uint8_t  rd;
+    uint8_t  funct3;
+    uint8_t  funct7;
+    uint32_t imm;
+};
+typedef struct Instruction Instruction;
+
+static Instruction decode_r_type(uint32_t word)
+{
+    Instruction instruction = {0};
+    instruction.opcode =  word        & 0x7F;
+    instruction.rd     = (word >> 7)  & 0x1F;
+    instruction.funct3 = (word >> 12) & 0x07;
+    instruction.rs1    = (word >> 15) & 0x1F;
+    instruction.rs2    = (word >> 20) & 0x1F;
+    instruction.funct7 =  word >> 25;
+    return instruction;
+};
+
+static Instruction decode_i_type(uint32_t word)
+{
+    Instruction instruction = {0};
+    instruction.opcode =  word        & 0x7F;
+    instruction.rd     = (word >> 7)  & 0x1F;
+    instruction.funct3 = (word >> 12) & 0x07;
+    instruction.rs1    = (word >> 15) & 0x1F;
+    instruction.imm    = sign_extend(word >> 20, 12);
+    return instruction;
+};
+
+static Instruction decode_s_type(uint32_t word)
+{
+    Instruction instruction = {0};
+    instruction.opcode =  word        & 0x7F;
+    instruction.funct3 = (word >> 12) & 0x07;
+    instruction.rs1    = (word >> 15) & 0x1F;
+    instruction.rs2    = (word >> 20) & 0x1F;
+    instruction.imm    = sign_extend(((word >> 7) & 0x1F) | (word >> 25), 12);
+    return instruction;
+};
+
+static Instruction decode_b_type(uint32_t word)
+{
+    Instruction instruction = decode_s_type(word);
+    instruction.imm = ((instruction.imm << 11) & 0x800) | (instruction.imm & 0xfffff7ff);
+    return instruction;
+};
+
+static Instruction decode_u_type(uint32_t word)
+{
+    Instruction instruction = {0};
+    instruction.opcode =  word        & 0x7F;
+    instruction.rd     = (word >> 7)  & 0x1F;
+    instruction.imm    =  word        & 0xFFFFF000;
+    return instruction;
+};
+
+static Instruction decode_j_type(uint32_t word)
+{
+    Instruction instruction = {0};
+    instruction.opcode =  word        & 0x7F;
+    instruction.rd     = (word >> 7)  & 0x1F;
+    instruction.imm    = sign_extend(
+        ((word & 0x80000000) >> 11) |
+        ((word & 0x000FF000) >> 0)  |
+        ((word & 0x00100000) >> 9)  |
+        ((word & 0x7FE00000) >> 20), 21);
+    return instruction;
+}
-- 
cgit