diff --git a/compiler-rt/cmake/config-ix.cmake b/compiler-rt/cmake/config-ix.cmake
index 4d3a5ab3d9d1e..482297a251b4b 100644
--- a/compiler-rt/cmake/config-ix.cmake
+++ b/compiler-rt/cmake/config-ix.cmake
@@ -564,8 +564,19 @@ else()
 endif()
 
 if (MSVC)
+  # Allow setting clang-cl's /winsysroot flag.
+  set(LLVM_WINSYSROOT "" CACHE STRING
+    "If set, argument to clang-cl's /winsysroot")
+
+  if (LLVM_WINSYSROOT)
+    set(MSVC_DIA_SDK_DIR "${LLVM_WINSYSROOT}/DIA SDK" CACHE PATH
+        "Path to the DIA SDK")
+  else()
+    set(MSVC_DIA_SDK_DIR "$ENV{VSINSTALLDIR}DIA SDK" CACHE PATH
+        "Path to the DIA SDK")
+  endif()
+
   # See if the DIA SDK is available and usable.
-  set(MSVC_DIA_SDK_DIR "$ENV{VSINSTALLDIR}DIA SDK")
   if (IS_DIRECTORY ${MSVC_DIA_SDK_DIR})
     set(CAN_SYMBOLIZE 1)
   else()
diff --git a/llvm/cmake/config-ix.cmake b/llvm/cmake/config-ix.cmake
index b590110d344e3..3569c2d1389af 100644
--- a/llvm/cmake/config-ix.cmake
+++ b/llvm/cmake/config-ix.cmake
@@ -503,10 +503,19 @@ if( MSVC )
   set(stricmp "_stricmp")
   set(strdup "_strdup")
 
-  # See if the DIA SDK is available and usable.
-  set(MSVC_DIA_SDK_DIR "$ENV{VSINSTALLDIR}DIA SDK" CACHE PATH
-      "Path to the DIA SDK")
+  # Allow setting clang-cl's /winsysroot flag.
+  set(LLVM_WINSYSROOT "" CACHE STRING
+    "If set, argument to clang-cl's /winsysroot")
 
+  if (LLVM_WINSYSROOT)
+    set(MSVC_DIA_SDK_DIR "${LLVM_WINSYSROOT}/DIA SDK" CACHE PATH
+        "Path to the DIA SDK")
+  else()
+    set(MSVC_DIA_SDK_DIR "$ENV{VSINSTALLDIR}DIA SDK" CACHE PATH
+        "Path to the DIA SDK")
+  endif()
+
+  # See if the DIA SDK is available and usable.
   # Due to a bug in MSVC 2013's installation software, it is possible
   # for MSVC 2013 to write the DIA SDK into the Visual Studio 2012
   # install directory.  If this happens, the installation is corrupt
diff --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
index 6df81f4c6f740..278a38a3b81c7 100644
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -458,9 +458,6 @@ if( MSVC )
     -D_UNICODE
   )
 
-  # Allow setting clang-cl's /winsysroot flag.
-  set(LLVM_WINSYSROOT "" CACHE STRING
-    "If set, argument to clang-cl's /winsysroot")
   if (LLVM_WINSYSROOT)
     if (NOT CLANG_CL)
       message(ERROR "LLVM_WINSYSROOT requires clang-cl")
diff --git a/llvm/utils/gn/secondary/llvm/lib/DebugInfo/PDB/BUILD.gn b/llvm/utils/gn/secondary/llvm/lib/DebugInfo/PDB/BUILD.gn
index 35f392b6d6463..07b34d41b9213 100644
--- a/llvm/utils/gn/secondary/llvm/lib/DebugInfo/PDB/BUILD.gn
+++ b/llvm/utils/gn/secondary/llvm/lib/DebugInfo/PDB/BUILD.gn
@@ -1,4 +1,5 @@
 import("//llvm/lib/DebugInfo/PDB/enable_dia.gni")
+import("//llvm/utils/gn/build/sysroot.gni")
 
 static_library("PDB") {
   output_name = "LLVMDebugInfoPDB"
@@ -122,6 +123,22 @@ static_library("PDB") {
       "DIA/DIASourceFile.cpp",
       "DIA/DIATable.cpp",
     ]
-    libs = [ "diaguids.lib" ]
+
+    dia_lib_path = ""
+    if (sysroot != "") {
+      assert(gn_version >= 1937,
+             "Building with sysroot and DIA requires a newer GN. " +
+                 "Run `python3 llvm\utils\gn\get.py` to update.")
+      include_dirs = [ "$sysroot/DIA SDK/include" ]
+      dia_lib_path = "$sysroot/DIA SDK/lib/"  # x86 .lib file is here.
+      if (current_cpu == "arm") {
+        dia_lib_path += "arm/"
+      } else if (current_cpu == "arm64") {
+        dia_lib_path += "arm64/"
+      } else if (current_cpu == "x64") {
+        dia_lib_path += "amd64/"
+      }
+    }
+    libs = [ "${dia_lib_path}diaguids.lib" ]
   }
 }
diff --git a/llvm/utils/gn/secondary/llvm/lib/DebugInfo/PDB/enable_dia.gni b/llvm/utils/gn/secondary/llvm/lib/DebugInfo/PDB/enable_dia.gni
index 3b655747a4fde..7c1cd3fbc8f30 100644
--- a/llvm/utils/gn/secondary/llvm/lib/DebugInfo/PDB/enable_dia.gni
+++ b/llvm/utils/gn/secondary/llvm/lib/DebugInfo/PDB/enable_dia.gni
@@ -1,6 +1,7 @@
 declare_args() {
   # Whether to build code that requires the Microsoft DIA SDK.
   # If this is set, %INCLUDE% must contain ".../DIA SDK/include"
-  # and %LIB% must contain ".../DIA SDK/lib/amd64".
+  # and %LIB% must contain ".../DIA SDK/lib/amd64". Or use
+  # llvm/utils/sysroot.py and set sysroot in args.gn.
   llvm_enable_dia_sdk = false
 }
diff --git a/llvm/utils/sysroot.py b/llvm/utils/sysroot.py
index 48b52ec712c96..599197dbd0a9e 100755
--- a/llvm/utils/sysroot.py
+++ b/llvm/utils/sysroot.py
@@ -13,6 +13,10 @@ def cmdout(cmd):
         return subprocess.check_output(cmd).decode(sys.stdout.encoding).strip()
 
     if sys.platform == 'win32':
+        def mkjunction(dst, src):
+            subprocess.check_call(['mklink', '/j', dst, src], shell=True)
+
+        os.mkdir(out_dir)
         p = os.getenv('ProgramFiles(x86)', 'C:\\Program Files (x86)')
 
         winsdk = os.getenv('WindowsSdkDir')
@@ -20,6 +24,8 @@ def cmdout(cmd):
             winsdk = os.path.join(p, 'Windows Kits', '10')
             print('%WindowsSdkDir% not set. You might want to run this from')
             print('a Visual Studio cmd prompt. Defaulting to', winsdk)
+        os.mkdir(os.path.join(out_dir, 'Windows Kits'))
+        mkjunction(os.path.join(out_dir, 'Windows Kits', '10'), winsdk)
 
         vswhere = os.path.join(
                 p, 'Microsoft Visual Studio', 'Installer', 'vswhere')
@@ -28,13 +34,12 @@ def cmdout(cmd):
                 [vswhere, '-latest', '-products', '*', '-requires', vcid,
                     '-property', 'installationPath'])
 
-        def mkjunction(dst, src):
-            subprocess.check_call(['mklink', '/j', dst, src], shell=True)
-        os.mkdir(out_dir)
         mkjunction(os.path.join(out_dir, 'VC'),
                    os.path.join(vsinstalldir, 'VC'))
-        os.mkdir(os.path.join(out_dir, 'Windows Kits'))
-        mkjunction(os.path.join(out_dir, 'Windows Kits', '10'), winsdk)
+        # Not all MSVC versions ship the DIA SDK, so the junction destination
+        # might not exist. That's fine.
+        mkjunction(os.path.join(out_dir, 'DIA SDK'),
+                   os.path.join(vsinstalldir, 'DIA SDK'))
     elif sys.platform == 'darwin':
         # The SDKs used by default in compiler-rt/cmake/base-config-ix.cmake.
         # COMPILER_RT_ENABLE_IOS defaults to on.