diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.h b/llvm/include/llvm/IR/RuntimeLibcalls.h
index 85db45e27e912..7f04a7f4ab5fd 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.h
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.h
@@ -128,9 +128,6 @@ struct RuntimeLibcallsInfo {
   }
 
 private:
-  static const RTLIB::LibcallImpl
-      DefaultLibcallImpls[RTLIB::UNKNOWN_LIBCALL + 1];
-
   /// Stores the implementation choice for each each libcall.
   RTLIB::LibcallImpl LibcallImpls[RTLIB::UNKNOWN_LIBCALL + 1] = {
       RTLIB::Unsupported};
@@ -178,8 +175,6 @@ struct RuntimeLibcallsInfo {
     return hasSinCos(TT) || TT.isPS();
   }
 
-  LLVM_ABI void initDefaultLibCallImpls();
-
   /// Generated by tablegen.
   void setTargetRuntimeLibcallSets(const Triple &TT,
                                    FloatABI::ABIType FloatABI);
diff --git a/llvm/include/llvm/IR/RuntimeLibcalls.td b/llvm/include/llvm/IR/RuntimeLibcalls.td
index 8ab63bd3d6b93..af339e2a55cf2 100644
--- a/llvm/include/llvm/IR/RuntimeLibcalls.td
+++ b/llvm/include/llvm/IR/RuntimeLibcalls.td
@@ -1581,7 +1581,9 @@ def HexagonSystemLibrary
     (add (sub DefaultLibcallImpls32,
     __adddf3, __divsf3, __udivsi3, __udivdi3,
     __umoddi3, __divdf3, __muldf3, __divsi3, __subdf3, sqrtf,
-    __divdi3, __umodsi3, __moddi3, __modsi3), HexagonLibcalls)>;
+    __divdi3, __umodsi3, __moddi3, __modsi3), HexagonLibcalls,
+    LibmHasSinCosF32, LibmHasSinCosF64, LibmHasSinCosF128,
+    exp10f, exp10, exp10l_f128)>;
 
 //===----------------------------------------------------------------------===//
 // Lanai Runtime Libcalls
@@ -2128,8 +2130,12 @@ def __memcpy_4 : RuntimeLibcallImpl<MEMCPY_ALIGN_4>;
 
 def isXCore : RuntimeLibcallPredicate<"TT.getArch() == Triple::xcore">;
 def XCoreSystemLibrary
-    : SystemRuntimeLibrary<isXCore, (add DefaultRuntimeLibcallImpls,
-                                        __memcpy_4)>;
+    : SystemRuntimeLibrary<isXCore,
+    (add DefaultRuntimeLibcallImpls,
+         exp10f, exp10, exp10l_f128,
+         __memcpy_4,
+         LibcallImpls<(add LibmF128Libcalls, LibmF128FiniteLibcalls), isGNUEnvironment>
+)>;
 
 //===----------------------------------------------------------------------===//
 // ZOS Runtime Libcalls
@@ -2246,3 +2252,27 @@ def WasmSystemLibrary
            CompilerRTOnlyInt64Libcalls, CompilerRTOnlyInt128Libcalls,
            exp10f, exp10,
            emscripten_return_address)>;
+
+//===----------------------------------------------------------------------===//
+// Legacy Default Runtime Libcalls
+//===----------------------------------------------------------------------===//
+
+// TODO: Should make every target explicit.
+def isDefaultLibcallArch : RuntimeLibcallPredicate<[{
+  TT.isMIPS() || TT.isLoongArch() || TT.isVE() || TT.isBPF() ||
+  TT.getArch() == Triple::csky || TT.getArch() == Triple::arc ||
+  TT.getArch() == Triple::m68k ||  TT.getArch() == Triple::xtensa ||
+  (TT.isSystemZ() && !TT.isOSzOS()) ||
+  TT.isSPIRV() || TT.isDXIL()
+}]>;
+
+
+def isArch64Bit : RuntimeLibcallPredicate<[{TT.isArch64Bit()}]>;
+def LegacyDefaultSystemLibrary
+    : SystemRuntimeLibrary<isDefaultLibcallArch,
+      (add DefaultRuntimeLibcallImpls,
+         LibmHasSinCosF32, LibmHasSinCosF64, LibmHasSinCosF128,
+         exp10f, exp10, exp10l_f128,
+         __powisf2, __powidf2, __powitf2_f128,
+         LibcallImpls<(add Int128RTLibcalls), isArch64Bit>
+)>;
diff --git a/llvm/lib/IR/RuntimeLibcalls.cpp b/llvm/lib/IR/RuntimeLibcalls.cpp
index 8c71dda4cdf67..df529bc013cac 100644
--- a/llvm/lib/IR/RuntimeLibcalls.cpp
+++ b/llvm/lib/IR/RuntimeLibcalls.cpp
@@ -7,6 +7,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/RuntimeLibcalls.h"
+#include "llvm/Support/Debug.h"
+
+#define DEBUG_TYPE "runtime-libcalls-info"
 
 using namespace llvm;
 using namespace RTLIB;
@@ -61,12 +64,6 @@ static void setARMLibcallNames(RuntimeLibcallsInfo &Info, const Triple &TT,
     Info.setLibcallImplCallingConv(Impl, CallingConv::ARM_AAPCS);
 }
 
-void RTLIB::RuntimeLibcallsInfo::initDefaultLibCallImpls() {
-  std::memcpy(LibcallImpls, DefaultLibcallImpls, sizeof(LibcallImpls));
-  static_assert(sizeof(LibcallImpls) == sizeof(DefaultLibcallImpls),
-                "libcall array size should match");
-}
-
 /// Set default libcall names. If a target wants to opt-out of a libcall it
 /// should be placed here.
 void RuntimeLibcallsInfo::initLibcalls(const Triple &TT,
@@ -75,10 +72,6 @@ void RuntimeLibcallsInfo::initLibcalls(const Triple &TT,
                                        EABI EABIVersion, StringRef ABIName) {
   setTargetRuntimeLibcallSets(TT, FloatABI);
 
-  // Early exit for targets that have fully ported to tablegen.
-  if (TT.isAMDGPU() || TT.isNVPTX() || TT.isWasm())
-    return;
-
   if (TT.isX86() || TT.isVE() || TT.isARM() || TT.isThumb()) {
     if (ExceptionModel == ExceptionHandling::SjLj)
       setLibcallImpl(RTLIB::UNWIND_RESUME, RTLIB::_Unwind_SjLj_Resume);
@@ -91,46 +84,17 @@ void RuntimeLibcallsInfo::initLibcalls(const Triple &TT,
     // FIXME: What about other targets?
     setLibcallImpl(RTLIB::FPEXT_F16_F32, RTLIB::__extendhfsf2);
     setLibcallImpl(RTLIB::FPROUND_F32_F16, RTLIB::__truncsfhf2);
-
-    if (!darwinHasExp10(TT)) {
-      setLibcallImpl(RTLIB::EXP10_F32, RTLIB::Unsupported);
-      setLibcallImpl(RTLIB::EXP10_F64, RTLIB::Unsupported);
-    }
   }
 
   if (TT.isOSOpenBSD()) {
     setLibcallImpl(RTLIB::STACKPROTECTOR_CHECK_FAIL, RTLIB::Unsupported);
   }
 
-  // Skip default manual processing for targets that have been mostly ported to
-  // tablegen for now. Eventually the rest of this should be deleted.
-  if (TT.isX86() || TT.isAArch64() || TT.isWasm() || TT.isPPC())
-    return;
-
   if (TT.isARM() || TT.isThumb()) {
     setARMLibcallNames(*this, TT, FloatABI, EABIVersion);
     return;
   }
 
-  if (hasSinCos(TT)) {
-    setLibcallImpl(RTLIB::SINCOS_F32, RTLIB::sincosf);
-    setLibcallImpl(RTLIB::SINCOS_F64, RTLIB::sincos);
-    setLibcallImpl(RTLIB::SINCOS_F128, RTLIB::sincos_f128);
-  }
-
-  setLibcallImpl(RTLIB::EXP10_F32, RTLIB::exp10f);
-  setLibcallImpl(RTLIB::EXP10_F64, RTLIB::exp10);
-  setLibcallImpl(RTLIB::EXP10_F128, RTLIB::exp10l_f128);
-
-  // These libcalls are only available in compiler-rt, not libgcc.
-  if (TT.isArch64Bit()) {
-    setLibcallImpl(RTLIB::SHL_I128, RTLIB::__ashlti3);
-    setLibcallImpl(RTLIB::SRL_I128, RTLIB::__lshrti3);
-    setLibcallImpl(RTLIB::SRA_I128, RTLIB::__ashrti3);
-    setLibcallImpl(RTLIB::MUL_I128, RTLIB::__multi3);
-    setLibcallImpl(RTLIB::MULO_I64, RTLIB::__mulodi4);
-  }
-
   if (TT.getArch() == Triple::ArchType::msp430) {
     setLibcallImplCallingConv(RTLIB::__mspabi_mpyll,
                               CallingConv::MSP430_BUILTIN);
diff --git a/llvm/test/TableGen/RuntimeLibcallEmitter.td b/llvm/test/TableGen/RuntimeLibcallEmitter.td
index a0061afab1db0..61c0468fbb7a1 100644
--- a/llvm/test/TableGen/RuntimeLibcallEmitter.td
+++ b/llvm/test/TableGen/RuntimeLibcallEmitter.td
@@ -104,18 +104,6 @@ def BlahLibrary : SystemRuntimeLibrary<isBlahArch, (add calloc, LibraryWithCondi
 // CHECK-NEXT: #endif
 
 // CHECK: #ifdef GET_INIT_RUNTIME_LIBCALL_NAMES
-// CHECK-NEXT: const RTLIB::LibcallImpl llvm::RTLIB::RuntimeLibcallsInfo::DefaultLibcallImpls[RTLIB::UNKNOWN_LIBCALL + 1] = {
-// CHECK-NEXT:   RTLIB::Unsupported, // RTLIB::BZERO
-// CHECK-NEXT:   RTLIB::Unsupported, // RTLIB::CALLOC
-// CHECK-NEXT:   RTLIB::Unsupported, // RTLIB::MEMCPY
-// CHECK-NEXT:   RTLIB::Unsupported, // RTLIB::MEMSET
-// CHECK-NEXT:   RTLIB::__ashlsi3, // RTLIB::SHL_I32
-// CHECK-NEXT:   RTLIB::sqrtl_f80, // RTLIB::SQRT_F80
-// CHECK-NEXT:   RTLIB::sqrtl_f128, // RTLIB::SQRT_F128
-// CHECK-NEXT:   RTLIB::__lshrdi3, // RTLIB::SRL_I64
-// CHECK-NEXT:   RTLIB::Unsupported
-// CHECK-NEXT: };
-// CHECK-EMPTY:
 // CHECK-NEXT: const char *const llvm::RTLIB::RuntimeLibcallsInfo::LibCallImplNames[RTLIB::NumLibcallImpls] = {
 // CHECK-NEXT: nullptr, // RTLIB::Unsupported
 // CHECK-NEXT: "___memcpy", // RTLIB::___memcpy
@@ -236,7 +224,7 @@ def BlahLibrary : SystemRuntimeLibrary<isBlahArch, (add calloc, LibraryWithCondi
 // CHECK-EMPTY:
 // CHECK-NEXT:   return;
 // CHECK-NEXT: }
-// CHECK-NEXT:  initDefaultLibCallImpls();
+// CHECK-NEXT:  LLVM_DEBUG(dbgs() << "no system runtime library applied to target \'" << TT.str() << "\'\n");
 // CHECK-NEXT: }
 // CHECK-EMPTY:
 // CHECK: #endif
diff --git a/llvm/utils/TableGen/Basic/RuntimeLibcallsEmitter.cpp b/llvm/utils/TableGen/Basic/RuntimeLibcallsEmitter.cpp
index 68bd1b5c9cb21..11f2075263a94 100644
--- a/llvm/utils/TableGen/Basic/RuntimeLibcallsEmitter.cpp
+++ b/llvm/utils/TableGen/Basic/RuntimeLibcallsEmitter.cpp
@@ -307,29 +307,6 @@ void RuntimeLibcallEmitter::emitGetInitRuntimeLibcallNames(
     raw_ostream &OS) const {
   // TODO: Emit libcall names as string offset table.
 
-  OS << "const RTLIB::LibcallImpl "
-        "llvm::RTLIB::RuntimeLibcallsInfo::"
-        "DefaultLibcallImpls[RTLIB::UNKNOWN_LIBCALL + 1] = {\n";
-
-  for (const RuntimeLibcall &LibCall : RuntimeLibcallDefList) {
-    auto I = LibCallToDefaultImpl.find(&LibCall);
-    if (I == LibCallToDefaultImpl.end()) {
-      OS << "  RTLIB::Unsupported,";
-    } else {
-      const RuntimeLibcallImpl *LibCallImpl = I->second;
-      OS << "  ";
-      LibCallImpl->emitEnumEntry(OS);
-      OS << ',';
-    }
-
-    OS << " // ";
-    LibCall.emitEnumEntry(OS);
-    OS << '\n';
-  }
-
-  OS << "  RTLIB::Unsupported\n"
-        "};\n\n";
-
   // Emit the implementation names
   OS << "const char *const llvm::RTLIB::RuntimeLibcallsInfo::"
         "LibCallImplNames[RTLIB::NumLibcallImpls] = {\n"
@@ -528,13 +505,11 @@ void RuntimeLibcallEmitter::emitSystemRuntimeLibrarySetCalls(
     TopLevelPredicate.emitEndIf(OS);
   }
 
-  // Fallback to the old default set for manual table entries.
-  //
-  // TODO: Remove this when targets have switched to using generated tables by
-  // default.
-  OS << "  initDefaultLibCallImpls();\n";
-
-  OS << "}\n\n";
+  // FIXME: This should be a fatal error. A few contexts are improperly relying
+  // on RuntimeLibcalls constructed with fully unknown triples.
+  OS << "  LLVM_DEBUG(dbgs() << \"no system runtime library applied to target "
+        "\\'\" << TT.str() << \"\\'\\n\");\n"
+        "}\n\n";
 }
 
 void RuntimeLibcallEmitter::run(raw_ostream &OS) {