diff --git a/llvm/include/llvm-c/module.modulemap b/llvm/include/llvm-c/module.modulemap
new file mode 100644
index 000000000000..2bcdbc17a5c3
--- /dev/null
+++ b/llvm/include/llvm-c/module.modulemap
@@ -0,0 +1,5 @@
+module LLVM_C {
+  requires cplusplus
+  umbrella "."
+  module * { export * }
+}
diff --git a/llvm/include/llvm/CMakeLists.txt b/llvm/include/llvm/CMakeLists.txt
index 0f5c63ded67a..ca4fd1338ed7 100644
--- a/llvm/include/llvm/CMakeLists.txt
+++ b/llvm/include/llvm/CMakeLists.txt
@@ -12,3 +12,9 @@ if( MSVC_IDE OR XCODE )
   set_target_properties(llvm_headers_do_not_build PROPERTIES FOLDER "Misc"
                         EXCLUDE_FROM_DEFAULT_BUILD ON)
 endif()
+
+# If we're doing an out-of-tree build, copy a module map for generated
+# header files into the build area.
+if (NOT "${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_BINARY_DIR}")
+  configure_file(module.modulemap.build module.modulemap COPYONLY)
+endif (NOT "${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_BINARY_DIR}")
diff --git a/llvm/include/llvm/module.modulemap b/llvm/include/llvm/module.modulemap
new file mode 100644
index 000000000000..1790a7242e5b
--- /dev/null
+++ b/llvm/include/llvm/module.modulemap
@@ -0,0 +1,177 @@
+module LLVM_Analysis {
+  requires cplusplus
+  umbrella "Analysis"
+  module * { export * }
+  exclude header "Analysis/BlockFrequencyInfoImpl.h"
+}
+
+module LLVM_AsmParser { requires cplusplus umbrella "AsmParser" module * { export * } }
+
+// A module covering CodeGen/ and Target/. These are intertwined
+// and codependent, and thus notionally form a single module.
+module LLVM_Backend {
+  requires cplusplus
+
+  module CodeGen {
+    umbrella "CodeGen"
+    module * { export * }
+
+    // FIXME: Why is this excluded?
+    exclude header "CodeGen/MachineValueType.h"
+
+    // Exclude these; they're intended to be included into only a single
+    // translation unit (or none) and aren't part of this module.
+    exclude header "CodeGen/CommandFlags.h"
+    exclude header "CodeGen/LinkAllAsmWriterComponents.h"
+    exclude header "CodeGen/LinkAllCodegenComponents.h"
+  }
+
+  module Target {
+    umbrella "Target"
+    module * { export * }
+  }
+
+  // FIXME: Where should this go?
+  module Analysis_BlockFrequencyInfoImpl {
+    header "Analysis/BlockFrequencyInfoImpl.h"
+    export *
+  }
+}
+
+module LLVM_Bitcode { requires cplusplus umbrella "Bitcode" module * { export * } }
+module LLVM_Config { requires cplusplus umbrella "Config" module * { export * } }
+module LLVM_DebugInfo { requires cplusplus umbrella "DebugInfo" module * { export * } }
+module LLVM_ExecutionEngine {
+  requires cplusplus
+
+  umbrella "ExecutionEngine"
+  module * { export * }
+
+  // Exclude this; it's an optional component of the ExecutionEngine.
+  exclude header "ExecutionEngine/OProfileWrapper.h"
+
+  // Exclude these; they're intended to be included into only a single
+  // translation unit (or none) and aren't part of this module.
+  exclude header "ExecutionEngine/JIT.h"
+  exclude header "ExecutionEngine/MCJIT.h"
+  exclude header "ExecutionEngine/Interpreter.h"
+}
+
+module LLVM_IR {
+  requires cplusplus
+
+  // FIXME: Is this the right place for these?
+  module Pass { header "Pass.h" export * }
+  module PassSupport { header "PassSupport.h" export * }
+  module PassAnalysisSupport { header "PassAnalysisSupport.h" export * }
+  module PassRegistry { header "PassRegistry.h" export * }
+  module InitializePasses { header "InitializePasses.h" export * }
+
+  umbrella "IR"
+  module * { export * }
+
+  // We cannot have llvm/PassManager.h and llvm/IR/PassManager.h in the same TU,
+  // so we can't include llvm/IR/PassManager.h in the IR module.
+  exclude header "IR/PassManager.h"
+  exclude header "IR/LegacyPassManager.h"
+
+  // Exclude this; it's intended for (repeated) textual inclusion.
+  exclude header "IR/Instruction.def"
+}
+
+module LLVM_LegacyPassManager {
+  requires cplusplus
+  module CompatInterface { header "PassManager.h" export * }
+  module Implementation { header "IR/LegacyPassManager.h" export * }
+}
+
+module LLVM_IR_PassManager {
+  requires cplusplus
+  // FIXME PR19358: This doesn't work! conflict LLVM_LegacyPassManager, "cannot use legacy pass manager and new pass manager in same file"
+  header "IR/PassManager.h"
+  export *
+}
+
+module LLVM_IRReader { requires cplusplus umbrella "IRReader" module * { export * } }
+module LLVM_LineEditor { requires cplusplus umbrella "LineEditor" module * { export * } }
+module LLVM_LTO { requires cplusplus umbrella "LTO" module * { export * } }
+
+module LLVM_MC {
+  requires cplusplus
+
+  // FIXME: Mislayered?
+  module Support_TargetRegistry {
+    header "Support/TargetRegistry.h"
+    export *
+  }
+
+  umbrella "MC"
+  module * { export * }
+
+  // Exclude this; it's fundamentally non-modular.
+  exclude header "MC/MCTargetOptionsCommandFlags.h"
+}
+
+module LLVM_Object { requires cplusplus umbrella "Object" module * { export * } }
+module LLVM_Option { requires cplusplus umbrella "Option" module * { export * } }
+module LLVM_TableGen { requires cplusplus umbrella "TableGen" module * { export * } }
+
+module LLVM_Transforms {
+  requires cplusplus
+  umbrella "Transforms"
+  module * { export * }
+
+  // FIXME: Excluded because it does bad things with the legacy pass manager.
+  exclude header "Transforms/IPO/PassManagerBuilder.h"
+}
+
+// A module covering ADT/ and Support/. These are intertwined and
+// codependent, and notionally form a single module.
+module LLVM_Utils {
+  module ADT {
+    requires cplusplus
+
+    umbrella "ADT"
+    module * { export * }
+  }
+
+  module Support {
+    requires cplusplus
+
+    umbrella "Support"
+    module * { export * }
+
+    // Exclude this; it's only included on Solaris.
+    exclude header "Support/Solaris.h"
+
+    // Exclude this; it's only included on AIX and fundamentally non-modular.
+    exclude header "Support/AIXDataTypesFix.h"
+
+    // Exclude this; it's fundamentally non-modular.
+    exclude header "Support/Debug.h"
+
+    // Exclude this; it's fundamentally non-modular.
+    exclude header "Support/PluginLoader.h"
+
+    // Exclude this; it's a weirdly-factored part of llvm-gcov and conflicts
+    // with the Analysis module (which also defines an llvm::GCOVOptions).
+    exclude header "Support/GCOV.h"
+
+    // FIXME: Mislayered?
+    exclude header "Support/TargetRegistry.h"
+  }
+}
+
+module LLVM_CodeGen_MachineValueType {
+  requires cplusplus
+  header "CodeGen/MachineValueType.h"
+  export *
+}
+
+// This is used for a $src == $build compilation. Otherwise we use
+// LLVM_Support_DataTypes_Build, defined in a module map that is
+// copied into the build area.
+module LLVM_Support_DataTypes_Src {
+  header "llvm/Support/DataTypes.h"
+  export *
+}
diff --git a/llvm/include/llvm/module.modulemap.build b/llvm/include/llvm/module.modulemap.build
new file mode 100644
index 000000000000..7150fe93935f
--- /dev/null
+++ b/llvm/include/llvm/module.modulemap.build
@@ -0,0 +1,5 @@
+// This is copied into the build area for a $src != $build compilation.
+module LLVM_Support_DataTypes {
+  header "Support/DataTypes.h"
+  export *
+}
diff --git a/llvm/lib/AsmParser/module.modulemap b/llvm/lib/AsmParser/module.modulemap
new file mode 100644
index 000000000000..cc300060b3f5
--- /dev/null
+++ b/llvm/lib/AsmParser/module.modulemap
@@ -0,0 +1 @@
+module AsmParser { requires cplusplus umbrella "." module * { export * } }
diff --git a/llvm/lib/Bitcode/module.modulemap b/llvm/lib/Bitcode/module.modulemap
new file mode 100644
index 000000000000..7df1a0a3c721
--- /dev/null
+++ b/llvm/lib/Bitcode/module.modulemap
@@ -0,0 +1 @@
+module Bitcode { requires cplusplus umbrella "." module * { export * } }
diff --git a/llvm/lib/CodeGen/module.modulemap b/llvm/lib/CodeGen/module.modulemap
new file mode 100644
index 000000000000..d4f68bcc6eed
--- /dev/null
+++ b/llvm/lib/CodeGen/module.modulemap
@@ -0,0 +1 @@
+module CodeGen { requires cplusplus umbrella "." module * { export * } }
diff --git a/llvm/lib/DebugInfo/module.modulemap b/llvm/lib/DebugInfo/module.modulemap
new file mode 100644
index 000000000000..1fe5ab130fd7
--- /dev/null
+++ b/llvm/lib/DebugInfo/module.modulemap
@@ -0,0 +1 @@
+module DebugInfo { requires cplusplus umbrella "." module * { export * } }
diff --git a/llvm/lib/IR/module.modulemap b/llvm/lib/IR/module.modulemap
new file mode 100644
index 000000000000..9698e9178349
--- /dev/null
+++ b/llvm/lib/IR/module.modulemap
@@ -0,0 +1 @@
+module IR { requires cplusplus umbrella "." module * { export * } }
diff --git a/llvm/lib/TableGen/module.modulemap b/llvm/lib/TableGen/module.modulemap
new file mode 100644
index 000000000000..8dac0a22c142
--- /dev/null
+++ b/llvm/lib/TableGen/module.modulemap
@@ -0,0 +1 @@
+module TableGen { requires cplusplus umbrella "." module * { export * } }
diff --git a/llvm/utils/TableGen/module.modulemap b/llvm/utils/TableGen/module.modulemap
new file mode 100644
index 000000000000..8871bbfd4a2f
--- /dev/null
+++ b/llvm/utils/TableGen/module.modulemap
@@ -0,0 +1,4 @@
+module TableGen {
+  umbrella "."
+  module * { export * }
+}