[HLSL][Driver] Make vk1.3 the default. (llvm#143384)

The HLSL driver currently defaults the triple to an unversioned os and
subarch when targeting SPIR-V. This means the SPIR-V backend decides the
default value. That is not a great option because a change the backend
could cause a change in Clang.

Now that we want to choose the default we need to consider the best
option. DXC currently defaults to Vulkan1.0. We are planning on not
supporting Vulkan1.0 in the Clang HLSL compiler because it is newer
versions of Vulkan are commonly supported on nearly all hardware, so
users do not use it.

Since we have to change from DXC anyway, we are using VK1.3. It has been
out long enough to be commonly available, and the initial implementation
of SPIR-V features for HLSL are assuming Vulkan 1.3.

---------

Co-authored-by: Nathan Gauër <[email protected]>

Author: s-perron

clang/lib/Driver/Driver.cpp

@@ -1596,28 +1596,27 @@ Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
       A->claim();
 
       if (Args.hasArg(options::OPT_spirv)) {
+        const llvm::StringMap<llvm::Triple::SubArchType> ValidTargets = {
+            {"vulkan1.2", llvm::Triple::SPIRVSubArch_v15},
+            {"vulkan1.3", llvm::Triple::SPIRVSubArch_v16}};
         llvm::Triple T(TargetTriple);
-        T.setArch(llvm::Triple::spirv);
-        T.setOS(llvm::Triple::Vulkan);
 
-        // Set specific Vulkan version if applicable.
+        // Set specific Vulkan version. Default to vulkan1.3.
+        auto TargetInfo = ValidTargets.find("vulkan1.3");
+        assert(TargetInfo != ValidTargets.end());
         if (const Arg *A = Args.getLastArg(options::OPT_fspv_target_env_EQ)) {
-          const llvm::StringMap<llvm::Triple::SubArchType> ValidTargets = {
-              {"vulkan1.2", llvm::Triple::SPIRVSubArch_v15},
-              {"vulkan1.3", llvm::Triple::SPIRVSubArch_v16}};
-
-          auto TargetInfo = ValidTargets.find(A->getValue());
-          if (TargetInfo != ValidTargets.end()) {
-            T.setOSName(TargetInfo->getKey());
-            T.setArch(llvm::Triple::spirv, TargetInfo->getValue());
-          } else {
+          TargetInfo = ValidTargets.find(A->getValue());
+          if (TargetInfo == ValidTargets.end()) {
             Diag(diag::err_drv_invalid_value)
                 << A->getAsString(Args) << A->getValue();
           }
           A->claim();
         }
-
-        TargetTriple = T.str();
+        if (TargetInfo != ValidTargets.end()) {
+          T.setOSName(TargetInfo->getKey());
+          T.setArch(llvm::Triple::spirv, TargetInfo->getValue());
+          TargetTriple = T.str();
+        }
       }
     } else {
       Diag(diag::err_drv_dxc_missing_target_profile);

clang/test/Driver/dxc_spirv.hlsl

@@ -3,7 +3,7 @@
 // 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-vulkan-compute"
+// CHECK: "-triple" "spirv1.6-unknown-vulkan1.3-compute"
 // CHECK-SAME: "-x" "hlsl"
 
 // CHECK-VULKAN12: "-triple" "spirv1.5-unknown-vulkan1.2-compute"