From c9cb051fae190acfc36813e4a23759fb9b9c3df3 Mon Sep 17 00:00:00 2001
From: Roland Reichwein <mail@reichwein.it>
Date: Mon, 16 Nov 2020 12:48:44 +0100
Subject: Implement hierarchical evaluation (WIP)

---
 asm/intel64/codes.cpp | 43 ++++++++++++++++++++++++++++++-------------
 1 file changed, 30 insertions(+), 13 deletions(-)

(limited to 'asm/intel64/codes.cpp')

diff --git a/asm/intel64/codes.cpp b/asm/intel64/codes.cpp
index 58d921f..9f82d37 100644
--- a/asm/intel64/codes.cpp
+++ b/asm/intel64/codes.cpp
@@ -1,5 +1,8 @@
 #include "codes.h"
 
+#include "minicc.h"
+#include "../operators.h"
+
 #include <exception>
 #include <unordered_map>
 
@@ -44,12 +47,13 @@ namespace {
   {"rdx", 2}, {"rdi", 7},
  };
 
-}
+} // namespace
 
 // Manual, page 530
 // Reg + Reg/Memory
-uint8_t ModRM(const std::string& reg, const std::string& rm) {
- uint8_t result{0b11000000}; // TODO: other than 11: Indexed forms of r/m
+std::vector<uint8_t> ModRM(const std::string& reg, const std::string& rm, int32_t disp) {
+ uint8_t result{}; // MOD is highest 2 bits, then 3 bits Reg, the 3 bits R/M
+ std::vector<uint8_t> displacement_bytes;
 
  size_t val_reg{};
  // reg
@@ -60,22 +64,35 @@ uint8_t ModRM(const std::string& reg, const std::string& rm) {
    throw std::runtime_error("ModRM: Bad digit in arg1: "s + reg);
   }
  } else { // reg
-  auto index1{ IndexOfRegister.find(reg) };
-  if (index1 == IndexOfRegister.end())
-   throw std::runtime_error("ModRM: Unknown register for arg1: "s + reg);
-  val_reg = index1->second;
+  val_reg = RegNo(reg);
  }
 
  result |= (val_reg << 3);
 
  // rm
- auto index2{ IndexOfRegister.find(rm) };
- if (index2 == IndexOfRegister.end())
-  throw std::runtime_error("Unknown register for arg2: "s + rm);
-
- result |= index2->second;
+ if (rm.size() > 2 && rm.front() == '[' && rm.back() == ']') { // indexed / MemPtr
+  uint8_t rm_bits {RegNo(rm.substr(1, rm.size() - 2))};
+  if (rm_bits == 4)
+   throw std::runtime_error("ICE: SIB byte not yet supported");
+
+  if (disp == 0 && rm_bits != 5) { // no displacement
+   // ignore: keep MOD == 00, no displacement bytes
+   if (rm_bits == 5)
+    throw std::runtime_error("ICE: [rbp] with now displacement is not supported"); // TODO: Support this, and SIB byte
+  } else if (disp >= -128 && disp < 128) {
+   result |= 0b01000000; // 8 bit displacement
+   displacement_bytes.push_back(uint8_t(disp));
+  } else {
+   result |= 0b10000000; // 32 bit displacement
+   displacement_bytes += to_little_endian(disp);
+  }
+  result |= rm_bits;
+ } else { // normal register access
+  result |= 0b11000000;
+  result |= RegNo(rm);
+ }
 
- return result;
+ return std::vector<uint8_t>{result} + displacement_bytes;
 }
 
 uint8_t RegNo(const std::string& reg)
-- 
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