interp: Add c.Lw compressed instruction.

Bug: 265372622

Test: berberis_host_tests/berberis_host_test

Change-Id: I0fdbde5761b7eca34badf8be10261ad281ba6a90

2 files changed, 62 insertions, 0 deletions

diff --git a/decoder/include/berberis/decoder/riscv64/decoder.h b/decoder/include/berberis/decoder/riscv64/decoder.h
index 677e715e..0e75d425 100644
--- a/decoder/include/berberis/decoder/riscv64/decoder.h
+++ b/decoder/include/berberis/decoder/riscv64/decoder.h
@@ -397,12 +397,31 @@ class Decoder {
       case CompressedOpcode::kFld:
         DecodeCFld();
         break;
+      case CompressedOpcode::kLw:
+        DecodeCLw();
+        break;
       default:
         insn_consumer_->Unimplemented();
     }
     return 2;
   }
 
+  void DecodeCLw() {
+    constexpr uint8_t kLwLow[4] = {0x0, 0x40, 0x04, 0x44};
+    uint8_t low_imm = GetBits<uint8_t, 5, 2>();
+    uint8_t high_imm = GetBits<uint8_t, 10, 3>();
+    uint8_t imm = (kLwLow[low_imm] | high_imm << 3);
+    uint8_t rd = GetBits<uint8_t, 2, 3>();
+    uint8_t rs = GetBits<uint8_t, 7, 3>();
+    const LoadArgs args = {
+        .opcode = LoadOpcode::kLw,
+        .dst = uint8_t(8 + rd),
+        .src = uint8_t(8 + rs),
+        .offset = imm,
+    };
+    insn_consumer_->Load(args);
+  }
+
   void DecodeCFld() {
     uint8_t low_imm = GetBits<uint8_t, 5, 2>();
     uint8_t high_imm = GetBits<uint8_t, 10, 3>();
diff --git a/interpreter/riscv64/interpreter_test.cc b/interpreter/riscv64/interpreter_test.cc
index 299b6e46..e041fdab 100644
--- a/interpreter/riscv64/interpreter_test.cc
+++ b/interpreter/riscv64/interpreter_test.cc
@@ -34,6 +34,14 @@ namespace {
 
 class Riscv64InterpreterTest : public ::testing::Test {
  public:
+  void InterpretCLw(uint16_t insn_bytes, uint64_t offset) {
+    auto code_start = ToGuestAddr(&insn_bytes);
+    state_.cpu.insn_addr = code_start;
+    SetXReg<8>(state_.cpu, ToGuestAddr(bit_cast<uint8_t*>(&kDataToLoad) - offset));
+    InterpretInsn(&state_);
+    EXPECT_EQ(GetXReg<8>(state_.cpu), uint64_t(int32_t(kDataToLoad)));
+  }
+
   void InterpretCFld(uint16_t insn_bytes, uint64_t offset) {
     auto code_start = ToGuestAddr(&insn_bytes);
     state_.cpu.insn_addr = code_start;
@@ -198,6 +206,41 @@ class Riscv64InterpreterTest : public ::testing::Test {
   ThreadState state_;
 };
 
+TEST_F(Riscv64InterpreterTest, CLw) {
+  union {
+    uint16_t offset;
+    struct {
+      uint8_t : 2;
+      uint8_t i2 : 1;
+      uint8_t i3_i5 : 3;
+      uint8_t i6 : 1;
+    } i_bits;
+  };
+  for (offset = uint8_t{0}; offset < uint8_t{128}; offset += 4) {
+    union {
+      int16_t parcel;
+      struct {
+        uint8_t low_opcode : 2;
+        uint8_t rd : 3;
+        uint8_t i6 : 1;
+        uint8_t i2 : 1;
+        uint8_t rs : 3;
+        uint8_t i3_i5 : 3;
+        uint8_t high_opcode : 3;
+      } __attribute__((__packed__));
+    } o_bits = {
+        .low_opcode = 0b00,
+        .rd = 0,
+        .i6 = i_bits.i6,
+        .i2 = i_bits.i2,
+        .rs = 0,
+        .i3_i5 = i_bits.i3_i5,
+        .high_opcode = 0b010,
+    };
+    InterpretCLw(o_bits.parcel, offset);
+  }
+}
+
 TEST_F(Riscv64InterpreterTest, CFld) {
   union {
     uint16_t offset;