diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -706,6 +706,11 @@
   "target profile option (-T) is missing">;
 def err_drv_hlsl_unsupported_target : Error<
   "HLSL code generation is unsupported for target '%0'">;
+def err_drv_dxil_bad_shader_required_in_target : Error<
+  "shader %select{model|stage}0 is required in target '%1' for DXIL generation">;
+
+def err_drv_dxil_bad_shader_unsupported : Error<
+  "shader %select{model|stage}0 '%1' in target '%2' is invalid for DXIL generation">;
 def warn_drv_dxc_missing_dxv : Warning<"dxv not found. "
     "Resulting DXIL will not be validated or signed for use in release environments.">,
     InGroup<DXILValidation>;
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -4143,10 +4143,22 @@
 
   // Validate options for HLSL
   if (Opts.HLSL) {
-    bool SupportedTarget = (T.getArch() == llvm::Triple::dxil ||
-                            T.getArch() == llvm::Triple::spirv) &&
-                           T.getOS() == llvm::Triple::ShaderModel;
-    if (!SupportedTarget)
+    if (T.isDXIL() || T.isSPIRV) {
+      enum { ShaderModel, ShaderStage };
+      if (T.getOSName().empty()) {
+        Diags.Report(diag::err_drv_dxil_bad_shader_required_in_target)
+            << ShaderModel << T.str();
+      } else if (!T.isShaderModelOS() || T.getOSVersion() == VersionTuple(0)) {
+        Diags.Report(diag::err_drv_dxil_bad_shader_unsupported)
+            << ShaderModel << T.getOSName() << T.str();
+      } else if (T.getEnvironmentName().empty()) {
+        Diags.Report(diag::err_drv_dxil_bad_shader_required_in_target)
+            << ShaderStage << T.str();
+      } else if (!T.isShaderStageEnvironment()) {
+        Diags.Report(diag::err_drv_dxil_bad_shader_unsupported)
+            << ShaderStage << T.getEnvironmentName() << T.str();
+      }
+    } else
       Diags.Report(diag::err_drv_hlsl_unsupported_target) << T.str();
   }
 
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -12394,10 +12394,7 @@
     case llvm::Triple::Library:
       break;
     default:
-      // TODO: This should probably just be llvm_unreachable and we should
-      // reject triples with random ABIs and such when we build the target.
-      // For now, crash.
-      llvm::report_fatal_error("Unhandled environment in triple");
+      llvm_unreachable("Unhandled environment in triple");
     }
   }
 }
diff --git a/clang/test/Driver/hlsl-lang-targets.hlsl b/clang/test/Driver/hlsl-lang-targets.hlsl
--- a/clang/test/Driver/hlsl-lang-targets.hlsl
+++ b/clang/test/Driver/hlsl-lang-targets.hlsl
@@ -1,14 +1,52 @@
-// RUN: not %clang -target x86_64-unknown-unknown %s 2>&1 | FileCheck %s --check-prefix=X86
-// RUN: not %clang -target dxil-unknown-unknown %s 2>&1 | FileCheck %s --check-prefix=DXIL
-// RUN: not %clang -target x86_64-unknown-shadermodel %s 2>&1 | FileCheck %s --check-prefix=SM
-// RUN: not %clang -target spirv64-unknown-unknown %s 2>&1 | FileCheck %s --check-prefix=SPIRV
+// Supported targets
+//
+// RUN: %clang -target dxil--shadermodel6.2-pixel %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-VALID %s
+// RUN: %clang -target dxil-unknown-shadermodel6.2-pixel %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-VALID %s
+// RUN: %clang -target dxil--shadermodel6.2-library %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-VALID %s
+// RUN: %clang -target dxil-unknown-shadermodel6.2-library %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-VALID %s
 
+// Empty shader model
+//
+// RUN: not %clang -target dxil %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-NO-OS %s
 
-// A completely unsupported target...
-// X86: error: HLSL code generation is unsupported for target 'x86_64-unknown-unknown'
+// Invalid shader models
+//
+// RUN: not %clang -target dxil--linux %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-OS %s
+// RUN: not %clang -target dxil--win32 %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-OS %s
+// RUN: not %clang -target dxil--unknown %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-OS %s
+// RUN: not %clang -target dxil--invalidos %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-OS %s
 
-// Poorly specified targets
-// DXIL: error: HLSL code generation is unsupported for target 'dxil-unknown-unknown'
-// SM: error: HLSL code generation is unsupported for target 'x86_64-unknown-shadermodel'
+// Bad shader model versions. Currently we just check for any version at all.
+//
+// RUN: not %clang -target dxil--shadermodel %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-OS %s
+// RUN: not %clang -target dxil--shadermodel0.0 %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-OS %s
 
-// FIXME// SPIRV: error: HLSL code generation is unsupported for target 'spirv64-unknown-unknown'
+// Empty shader stage
+//
+// RUN: not %clang -target dxil-shadermodel6.2 %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-NO-ENV %s
+// RUN: not %clang -target dxil--shadermodel6.2 %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-NO-ENV %s
+// RUN: not %clang -target dxil--shadermodel6.2 %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-NO-ENV %s
+
+// Invalid shader stages
+//
+// RUN: not %clang -target dxil--shadermodel6.2-unknown %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-ENV %s
+// RUN: not %clang -target dxil--shadermodel6.2-invalidenvironment %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-ENV %s
+// RUN: not %clang -target dxil--shadermodel6.2-eabi %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-ENV %s
+// RUN: not %clang -target dxil--shadermodel6.2-msvc %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-ENV %s
+
+// Non-dxil targets
+//
+// RUN: not %clang -target x86_64-unknown-unknown %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-TARGET %s
+// RUN: not %clang -target x86_64-linux %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-TARGET %s
+// RUN: not %clang -target amdgcn %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-TARGET %s
+// RUN: not %clang -target spirv64-unknown-unknown %s -S -o /dev/null 2>&1 | FileCheck --check-prefix=CHECK-BAD-TARGET %s
+
+// CHECK-VALID-NOT: error:
+// CHECK-NO-OS: error: shader model is required in target '{{.*}}' for DXIL generation
+// CHECK-BAD-OS: error: shader model '{{.*}}' in target '{{.*}}' is invalid for DXIL generation
+// CHECK-NO-ENV: error: shader stage is required in target '{{.*}}' for DXIL generation
+// CHECK-BAD-ENV: error: shader stage '{{.*}}' in target '{{.*}}' is invalid for DXIL generation
+// CHECK-BAD-TARGET: error: HLSL code generation is unsupported for target '{{.*}}'
+
+[shader("pixel")]
+void main() {}
diff --git a/llvm/include/llvm/TargetParser/Triple.h b/llvm/include/llvm/TargetParser/Triple.h
--- a/llvm/include/llvm/TargetParser/Triple.h
+++ b/llvm/include/llvm/TargetParser/Triple.h
@@ -271,7 +271,9 @@
     Callable,
     Mesh,
     Amplification,
+
     OpenHOS,
+
     LastEnvironmentType = OpenHOS
   };
   enum ObjectFormatType {
@@ -756,6 +758,22 @@
     return getArch() == Triple::dxil;
   }
 
+  bool isShaderModelOS() const {
+    return getOS() == Triple::ShaderModel;
+  }
+
+  bool isShaderStageEnvironment() const {
+    EnvironmentType Env = getEnvironment();
+    return Env == Triple::Pixel || Env == Triple::Vertex ||
+           Env == Triple::Geometry || Env == Triple::Hull ||
+           Env == Triple::Domain || Env == Triple::Compute ||
+           Env == Triple::Library || Env == Triple::RayGeneration ||
+           Env == Triple::Intersection || Env == Triple::AnyHit ||
+           Env == Triple::ClosestHit || Env == Triple::Miss ||
+           Env == Triple::Callable || Env == Triple::Mesh ||
+           Env == Triple::Amplification;
+  }
+
   /// Tests whether the target is SPIR (32- or 64-bit).
   bool isSPIR() const {
     return getArch() == Triple::spir || getArch() == Triple::spir64;