Index: llvm/include/llvm/TargetParser/Triple.h
===================================================================
--- llvm/include/llvm/TargetParser/Triple.h
+++ llvm/include/llvm/TargetParser/Triple.h
@@ -105,6 +105,7 @@
     wasm64,         // WebAssembly with 64-bit pointers
     renderscript32, // 32-bit RenderScript
     renderscript64, // 64-bit RenderScript
+    rl78,           // Renesas RL78
     ve,             // NEC SX-Aurora Vector Engine
     LastArchType = ve
   };
Index: llvm/lib/TargetParser/Triple.cpp
===================================================================
--- llvm/lib/TargetParser/Triple.cpp
+++ llvm/lib/TargetParser/Triple.cpp
@@ -64,6 +64,7 @@
   case renderscript64: return "renderscript64";
   case riscv32:        return "riscv32";
   case riscv64:        return "riscv64";
+  case rl78:           return "rl78";
   case shave:          return "shave";
   case sparc:          return "sparc";
   case sparcel:        return "sparcel";
@@ -166,6 +167,8 @@
   case riscv32:
   case riscv64:     return "riscv";
 
+  case rl78:        return "rl78";
+
   case ve:          return "ve";
   case csky:        return "csky";
 
@@ -389,6 +392,7 @@
     .Case("wasm64", wasm64)
     .Case("renderscript32", renderscript32)
     .Case("renderscript64", renderscript64)
+    .Case("rl78", rl78)
     .Case("ve", ve)
     .Case("csky", csky)
     .Case("loongarch32", loongarch32)
@@ -528,6 +532,7 @@
     .Case("lanai", Triple::lanai)
     .Case("renderscript32", Triple::renderscript32)
     .Case("renderscript64", Triple::renderscript64)
+    .Case("rl78", Triple::rl78)
     .Case("shave", Triple::shave)
     .Case("ve", Triple::ve)
     .Case("wasm32", Triple::wasm32)
@@ -838,6 +843,7 @@
   case Triple::renderscript64:
   case Triple::riscv32:
   case Triple::riscv64:
+  case Triple::rl78:
   case Triple::shave:
   case Triple::sparc:
   case Triple::sparcel:
@@ -1394,6 +1400,7 @@
 
   case llvm::Triple::avr:
   case llvm::Triple::msp430:
+  case llvm::Triple::rl78:
     return 16;
 
   case llvm::Triple::aarch64_32:
@@ -1482,6 +1489,7 @@
   case Triple::bpfeb:
   case Triple::bpfel:
   case Triple::msp430:
+  case Triple::rl78:
   case Triple::systemz:
   case Triple::ve:
     T.setArch(UnknownArch);
@@ -1567,6 +1575,7 @@
   case Triple::m68k:
   case Triple::msp430:
   case Triple::r600:
+  case Triple::rl78:
   case Triple::shave:
   case Triple::sparcel:
   case Triple::tce:
@@ -1661,6 +1670,7 @@
   case Triple::renderscript64:
   case Triple::riscv32:
   case Triple::riscv64:
+  case Triple::rl78:
   case Triple::shave:
   case Triple::spir64:
   case Triple::spir:
@@ -1769,6 +1779,7 @@
   case Triple::renderscript64:
   case Triple::riscv32:
   case Triple::riscv64:
+  case Triple::rl78:
   case Triple::shave:
   case Triple::sparcel:
   case Triple::spir64:
Index: llvm/unittests/TargetParser/TripleTest.cpp
===================================================================
--- llvm/unittests/TargetParser/TripleTest.cpp
+++ llvm/unittests/TargetParser/TripleTest.cpp
@@ -888,6 +888,18 @@
   EXPECT_EQ(Triple::LiteOS, T.getOS());
   EXPECT_EQ(Triple::UnknownEnvironment, T.getEnvironment());
 
+  T = Triple("rl78");
+  EXPECT_EQ(Triple::rl78, T.getArch());
+  EXPECT_EQ(Triple::UnknownVendor, T.getVendor());
+  EXPECT_EQ(Triple::UnknownOS, T.getOS());
+  EXPECT_EQ(Triple::UnknownEnvironment, T.getEnvironment());
+
+  T = Triple("rl78-unknown-unknown");
+  EXPECT_EQ(Triple::rl78, T.getArch());
+  EXPECT_EQ(Triple::UnknownVendor, T.getVendor());
+  EXPECT_EQ(Triple::UnknownOS, T.getOS());
+  EXPECT_EQ(Triple::UnknownEnvironment, T.getEnvironment());
+
   T = Triple("huh");
   EXPECT_EQ(Triple::UnknownArch, T.getArch());
 }
@@ -1254,6 +1266,11 @@
   EXPECT_FALSE(T.isArch16Bit());
   EXPECT_TRUE(T.isArch32Bit());
   EXPECT_FALSE(T.isArch64Bit());
+
+  T.setArch(Triple::rl78);
+  EXPECT_TRUE(T.isArch16Bit());
+  EXPECT_FALSE(T.isArch32Bit());
+  EXPECT_FALSE(T.isArch64Bit());
 }
 
 TEST(TripleTest, BitWidthArchVariants) {
@@ -1605,6 +1622,11 @@
   EXPECT_TRUE(T.isLittleEndian());
   EXPECT_EQ(Triple::UnknownArch, T.getBigEndianArchVariant().getArch());
   EXPECT_EQ(Triple::dxil, T.getLittleEndianArchVariant().getArch());
+
+  T.setArch(Triple::rl78);
+  EXPECT_TRUE(T.isLittleEndian());
+  EXPECT_EQ(Triple::UnknownArch, T.getBigEndianArchVariant().getArch());
+  EXPECT_EQ(Triple::rl78, T.getLittleEndianArchVariant().getArch());
 }
 
 TEST(TripleTest, getOSVersion) {