add decompiler

decompiler/Function/BasicBlocks.cpp

@@ -0,0 +1,51 @@
+#include <algorithm>
+#include <cassert>
+#include "BasicBlocks.h"
+#include "decompiler/ObjectFile/LinkedObjectFile.h"
+#include "decompiler/Disasm/InstructionMatching.h"
+
+/*!
+ * Find all basic blocks in a function.
+ * All delay slot instructions are grouped with the branch instruction.
+ * This is done by finding all "dividers", which are after branch delay instructions and before
+ * branch destinations, then sorting them, ignoring duplicates, and creating the blocks.
+ */
+std::vector<BasicBlock> find_blocks_in_function(const LinkedObjectFile& file,
+                                                int seg,
+                                                const Function& func) {
+  std::vector<BasicBlock> basic_blocks;
+
+  // note - the first word of a function is the "function" type and should go in any basic block
+  std::vector<int> dividers = {0, int(func.instructions.size())};
+
+  for (int i = 0; i < int(func.instructions.size()); i++) {
+    const auto& instr = func.instructions.at(i);
+    const auto& instr_info = instr.get_info();
+
+    if (instr_info.is_branch || instr_info.is_branch_likely) {
+      // make sure the delay slot of this branch is included in the function
+      assert(i + func.start_word < func.end_word - 1);
+      // divider after delay slot
+      dividers.push_back(i + 2);
+      auto label_id = instr.get_label_target();
+      assert(label_id != -1);
+      const auto& label = file.labels.at(label_id);
+      // should only jump to within our own function
+      assert(label.target_segment == seg);
+      assert(label.offset / 4 > func.start_word);
+      assert(label.offset / 4 < func.end_word - 1);
+      dividers.push_back(label.offset / 4 - func.start_word);
+    }
+  }
+
+  std::sort(dividers.begin(), dividers.end());
+
+  for (size_t i = 0; i < dividers.size() - 1; i++) {
+    if (dividers[i] != dividers[i + 1]) {
+      basic_blocks.emplace_back(dividers[i], dividers[i + 1]);
+      assert(dividers[i] >= 0);
+    }
+  }
+
+  return basic_blocks;
+}