fix cond with else that is empty bug (#470)

decompiler/Disasm/InstructionParser.cpp

@@ -43,7 +43,7 @@ InstructionParser::InstructionParser() {
                  InstructionKind::BGTZ,   InstructionKind::BLTZL,  InstructionKind::BGTZL,
                  InstructionKind::BGEZL,  InstructionKind::MTC1,   InstructionKind::MFC1,
                  InstructionKind::MFLO,   InstructionKind::MFHI,   InstructionKind::MTLO1,
-                 InstructionKind::MFLO1,  InstructionKind::SYNCL}) {
+                 InstructionKind::MFLO1,  InstructionKind::SYNCL,  InstructionKind::PCPYUD}) {
     auto& info = gOpcodeInfo[int(i)];
     if (info.defined) {
       m_opcode_name_lookup[info.name] = int(i);

decompiler/Function/CfgVtx.cpp

@@ -1248,7 +1248,7 @@ bool ControlFlowGraph::find_cond_w_empty_else() {
       return true;
     }
 
-    //        printf("cwe try %s %s\n", c0->to_string().c_str(), b0->to_string().c_str());
+    // printf("cwe try %s %s\n", c0->to_string().c_str(), b0->to_string().c_str());
 
     // first condition should have the _option_ to fall through to first body
     if (c0->succ_ft != b0 || c0->end_branch.kind != CfgVtx::DelaySlotKind::NOP) {
@@ -1290,11 +1290,10 @@ bool ControlFlowGraph::find_cond_w_empty_else() {
       else_block = end_block;
     }
 
-    if (else_block->succ_branch) {
-      return true;
-    }
-
-    assert(!else_block->end_branch.has_branch);
+    // the else code is empty, so the else block is the same as the end block.
+    // in this empty else case, we don't care what the "else" block end conditions are.
+    // else must fall through to end with no possible branch.
+    // it's not our problem to deal with the end block's branching.;
 
     std::vector<CondWithElse::Entry> entries = {{c0, b0}};
     auto* prev_condition = c0;

decompiler/Function/Function.h

@@ -109,6 +109,7 @@ class Function {
   std::vector<Instruction> instructions;
   std::vector<BasicBlock> basic_blocks;
   std::shared_ptr<ControlFlowGraph> cfg = nullptr;
+  bool cfg_ok = false;
 
   int prologue_start = -1;
   int prologue_end = -1;

decompiler/ObjectFile/ObjectFileDB_IR2.cpp

@@ -211,6 +211,8 @@ void ObjectFileDB::ir2_basic_block_pass() {
         lg::warn("Function {} from {} failed to build control flow graph!",
                  func.guessed_name.to_string(), data.to_unique_name());
         failed_to_build_cfg++;
+      } else {
+        func.cfg_ok = true;
       }
     }
 
@@ -237,6 +239,9 @@ void ObjectFileDB::ir2_stack_spill_slot_pass() {
   int functions_with_spills = 0;
   int total_slots = 0;
   for_each_function_def_order([&](Function& func, int, ObjectFileData&) {
+    if (!func.cfg_ok) {
+      return;
+    }
     auto spill_map = build_spill_map(func.instructions, {func.prologue_end, func.epilogue_start});
     auto map_size = spill_map.size();
     if (map_size) {
@@ -259,6 +264,9 @@ void ObjectFileDB::ir2_atomic_op_pass(const Config& config) {
   int attempted = 0;
   int successful = 0;
   for_each_function_def_order([&](Function& func, int segment_id, ObjectFileData& data) {
+    if (!func.cfg_ok) {
+      return;
+    }
     (void)segment_id;
     total_functions++;
     if (!func.suspected_asm) {

test/decompiler/FormRegressionTest.cpp

@@ -153,6 +153,8 @@ std::unique_ptr<FormRegressionTest::TestData> FormRegressionTest::make_function(
   EXPECT_TRUE(test->func.cfg->is_fully_resolved());
   if (!test->func.cfg->is_fully_resolved()) {
     fmt::print("CFG:\n{}\n", test->func.cfg->to_dot());
+  } else {
+    test->func.cfg_ok = true;
   }
 
   // find stack spill slots

test/decompiler/test_FormBeforeExpressions.cpp

@@ -123,7 +123,7 @@ TEST_F(FormRegressionTest, Min) {
   std::string func =
       "    sll r0, r0, 0\n"
       "    or v0, a0, r0\n"
-      "    or v1, a1, r0 \n"
+      "    or v1, a1, r0\n"
       "    slt a0, v0, v1\n"
       "    movz v0, v1, a0\n"
       "    jr ra\n"
@@ -179,7 +179,7 @@ TEST_F(FormRegressionTest, FormatString) {
       "    jalr ra, t9\n"
       "    sll v0, ra, 0\n"
 
-      "    or v0, gp, r0 \n"
+      "    or v0, gp, r0\n"
       "    ld ra, 0(sp)\n"
       "    ld fp, 8(sp)\n"
       "    lq gp, 16(sp)\n"
@@ -880,4 +880,4 @@ TEST_F(FormRegressionTest, TypeOf) {
       "  (ret-value v0-0)\n"
       "  )";
   test_no_expr(func, type, expected, false);
-}
+}