diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -106,6 +106,15 @@
       {Builtin::BI__builtin_nexttowardf128, "__nexttowardieee128"},
   };
 
+  // The AIX library functions frexpl, ldexpl, and modfl are for 128-bit
+  // IBM 'long double' (i.e. __ibm128). Map to the 'double' versions
+  // if it is 64-bit 'long double' mode.
+  static SmallDenseMap<unsigned, StringRef, 4> AIXLongDouble64Builtins{
+      {Builtin::BI__builtin_frexpl, "frexp"},
+      {Builtin::BI__builtin_ldexpl, "ldexp"},
+      {Builtin::BI__builtin_modfl, "modf"},
+  };
+
   // If the builtin has been declared explicitly with an assembler label,
   // use the mangled name. This differs from the plain label on platforms
   // that prefix labels.
@@ -118,6 +127,12 @@
         &getTarget().getLongDoubleFormat() == &llvm::APFloat::IEEEquad() &&
         F128Builtins.find(BuiltinID) != F128Builtins.end())
       Name = F128Builtins[BuiltinID];
+    else if (getTriple().isOSAIX() &&
+             &getTarget().getLongDoubleFormat() ==
+                 &llvm::APFloat::IEEEdouble() &&
+             AIXLongDouble64Builtins.find(BuiltinID) !=
+                 AIXLongDouble64Builtins.end())
+      Name = AIXLongDouble64Builtins[BuiltinID];
     else
       Name = Context.BuiltinInfo.getName(BuiltinID) + 10;
   }
diff --git a/clang/test/CodeGen/aix-builtin-mapping.c b/clang/test/CodeGen/aix-builtin-mapping.c
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGen/aix-builtin-mapping.c
@@ -0,0 +1,22 @@
+// AIX library functions frexpl, ldexpl, and modfl are for 128-bit IBM
+// 'long double' (i.e. __ibm128). Check that the compiler generates
+// calls to the 'double' versions for corresponding builtin functions in
+// 64-bit 'long double' mode.
+
+// RUN: %clang_cc1 -triple powerpc-ibm-aix -mlong-double-64 -emit-llvm -o - %s | FileCheck -check-prefix=CHECK %s
+// RUN: %clang_cc1 -triple powerpc64-ibm-aix -mlong-double-64 -emit-llvm -o - %s | FileCheck -check-prefix=CHECK %s
+
+int main()
+{
+  int DummyInt;
+  long double DummyLongDouble;
+  long double returnValue;
+
+  returnValue = __builtin_modfl(1.0L, &DummyLongDouble);
+  returnValue = __builtin_frexpl(0.0L, &DummyInt);
+  returnValue = __builtin_ldexpl(1.0L, 1);
+}
+
+// CHECK: %call = call double @modf(double noundef 1.000000e+00, ptr noundef %DummyLongDouble) #3
+// CHECK: %call1 = call double @frexp(double noundef 0.000000e+00, ptr noundef %DummyInt) #3
+// CHECK: %call2 = call double @ldexp(double noundef 1.000000e+00, i32 noundef {{(signext )?}}1) #4