[HLSL][SPIR-V] Add support -fspv-target-env opt (#78611)

Add the -fspv-target-env option to the clang-dxc compatibility driver to
specify the SPIR-V target environment, which is propagated to the target
Triple.

clang/include/clang/Driver/Options.td

@@ -8479,3 +8479,6 @@ def : Option<["/", "-"], "Qembed_debug", KIND_FLAG>, Group<dxc_Group>,
   HelpText<"Embed PDB in shader container (ignored)">;
 def spirv : DXCFlag<"spirv">,
   HelpText<"Generate SPIR-V code">;
+def fspv_target_env_EQ : Joined<["-"], "fspv-target-env=">, Group<dxc_Group>,
+  HelpText<"Specify the target environment">,
+  Values<"vulkan1.2, vulkan1.3">;

clang/lib/Driver/Driver.cpp

@@ -1310,10 +1310,23 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
 
       A->claim();
 
-      // TODO: Specify Vulkan target environment somewhere in the triple.
       if (Args.hasArg(options::OPT_spirv)) {
         llvm::Triple T(TargetTriple);
         T.setArch(llvm::Triple::spirv);
+        T.setOS(llvm::Triple::Vulkan);
+
+        // Set specific Vulkan version if applicable.
+        if (const Arg *A = Args.getLastArg(options::OPT_fspv_target_env_EQ)) {
+          const llvm::StringSet<> ValidValues = {"vulkan1.2", "vulkan1.3"};
+          if (ValidValues.contains(A->getValue())) {
+            T.setOSName(A->getValue());
+          } else {
+            Diag(diag::err_drv_invalid_value)
+                << A->getAsString(Args) << A->getValue();
+          }
+          A->claim();
+        }
+
         TargetTriple = T.str();
       }
     } else {

clang/test/Driver/dxc_spirv.hlsl

@@ -1,4 +1,13 @@
 // RUN: %clang_dxc -T cs_6_0 -spirv -### %s 2>&1 | FileCheck %s
+// RUN: %clang_dxc -T cs_6_0 -spirv -fspv-target-env=vulkan1.2 -### %s 2>&1 | FileCheck %s --check-prefix=CHECK-VULKAN12
+// RUN: %clang_dxc -T cs_6_0 -spirv -fspv-target-env=vulkan1.3 -### %s 2>&1 | FileCheck %s --check-prefix=CHECK-VULKAN13
+// RUN: not %clang_dxc -T cs_6_0 -spirv -fspv-target-env=vulkan1.0 -### %s 2>&1 | FileCheck %s --check-prefix=CHECK-ERROR
 
-// CHECK: "-triple" "spirv-unknown-shadermodel6.0-compute"
+// CHECK: "-triple" "spirv-unknown-vulkan-compute"
 // CHECK-SAME: "-x" "hlsl"
+
+// CHECK-VULKAN12: "-triple" "spirv-unknown-vulkan1.2-compute"
+
+// CHECK-VULKAN13: "-triple" "spirv-unknown-vulkan1.3-compute"
+
+// CHECK-ERROR: error: invalid value 'vulkan1.0' in '-fspv-target-env=vulkan1.0'