From 02153da4d5954261f6649e2980bc88f6d29e45a6 Mon Sep 17 00:00:00 2001
From: Roland Reichwein <mail@reichwein.it>
Date: Sat, 31 Aug 2024 18:29:58 +0200
Subject: ARM assembler (WIP)

---
 asm/arm/instruction.h | 109 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 asm/arm/instruction.h

(limited to 'asm/arm/instruction.h')

diff --git a/asm/arm/instruction.h b/asm/arm/instruction.h
new file mode 100644
index 0000000..224cc6e
--- /dev/null
+++ b/asm/arm/instruction.h
@@ -0,0 +1,109 @@
+#pragma once
+
+#include <memory>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+using namespace std::string_literals;
+
+using code_sequence = std::vector<uint8_t>;
+
+template<typename from_t>
+code_sequence to_code_sequence(from_t v);
+
+template<>
+code_sequence to_code_sequence<uint16_t>(uint16_t v) {
+ return code_sequence{static_cast<uint8_t>(v & 0xFF), static_cast<uint8_t>(v >> 8)};
+}
+
+template<>
+code_sequence to_code_sequence<uint32_t>(uint32_t v) {
+ return code_sequence{static_cast<uint8_t>(v & 0xFF), static_cast<uint8_t>(v >> 8), static_cast<uint8_t>(v >> 16),static_cast<uint8_t>(v >> 24) };
+}
+
+uint32_t high_bits(uint8_t number)
+{
+ return ~((static_cast<uint32_t>(1) << (32 - number)) - 1);
+}
+
+// Identify operator with leading bits
+class Pattern
+{
+public:
+ Pattern(uint32_t bits, uint32_t mask): _bits{bits}, _mask{mask} {}
+
+ template<typename T>
+ T encode()
+ {
+  return static_cast<T>(_bits);
+ }
+
+
+private:
+ uint32_t _bits;
+ uint32_t _mask;
+};
+
+class Operand
+{
+protected:
+ Operand(uint8_t pos): _pos(pos){}
+private:
+ uint8_t _pos;
+};
+
+class Register: public Operand
+{
+public:
+ Register(uint8_t pos): Operand{pos} {};
+};
+
+class Immediate: public Operand
+{
+public:
+ Immediate(uint8_t pos, uint8_t bits): Operand{pos}, _bits{bits} {}
+private:
+ uint8_t _bits;
+};
+
+using Operands = std::vector<std::shared_ptr<Operand>>;
+
+// Pattern [, Operand, ...]
+class Instruction
+{
+public:
+ Instruction(const std::string& mnemonic, uint8_t size, Pattern pattern, Operands operands): _mnemonic(mnemonic), _size(size), _pattern(pattern), _operands(operands) {}
+ code_sequence encode(const std::vector<std::string>& arguments)
+ {
+  if (_size == 2) { // 16 bit thumb insn
+   uint16_t result{ _pattern.encode<uint16_t>()};
+   return to_code_sequence(result);
+  } else if (_size == 4) { // 32 bit thumb insn
+   uint32_t result{ _pattern.encode<uint32_t>()};
+   return to_code_sequence(result);
+  } else {
+   throw std::runtime_error("Unsupported instruction size "s + std::to_string(_size));
+  }
+ }
+
+private:
+ std::string _mnemonic;
+ uint8_t _size;
+ Pattern _pattern;
+ Operands _operands;
+};
+
+namespace {
+ // factory functions
+ std::shared_ptr<Operand> imm(uint8_t pos, uint8_t size){ return std::make_shared<Immediate>(pos, size); };
+ std::shared_ptr<Operand> reg(uint8_t pos) { return std::make_shared<Register>(pos); };
+
+ std::vector<Instruction> insns{
+  {"adcs", 2, Pattern(0x4140, high_bits(10)), Operands{reg(0), reg(3)}},
+
+  {"lsls", 2, Pattern(0x0000, high_bits(5)), Operands{reg(0), reg(3), imm(6, 5)}}
+ };
+};
+
+
-- 
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