[skslc] Support HLSL output

- skslc can now generate HLSL using spirv-cross if invokved with an output
file with the ".hlsl" extension
- The SkSL::SPIRVtoHLSL function used to be conditionally compiled based
on the SK_USE_DIRECT3D define, which gates D3D support for the entire
gpu backend. This function is now conditionally compiled using a new,
more narrowly scoped define, which is always enabled when building
skslc.

Bug: skia:12691
Test: Run:
Change-Id: I6967c26ab28954ec09e1c62513187c8986135290
      1. ./skslc ../../resources/sksl/spirv/Ossfuzz35916.sksl TEST.hlsl
      2. ./dxc -T ps_6_7 TEST.hlsl
      Ensure that 1 runs without any errors and 2 does not detect any
      issues in the hlsl.
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/482257
Auto-Submit: Arman Uguray <armansito@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

BUILD.gn

@@ -627,6 +627,7 @@ if (skia_compile_sksl_tests) {
     defines = [
       "SKSL_STANDALONE",
       "SK_DISABLE_TRACING",
+      "SK_ENABLE_SPIRV_CROSS",
       "SK_ENABLE_SPIRV_VALIDATION",
     ]
     sources = [
@@ -668,6 +669,7 @@ if (skia_compile_sksl_tests) {
       ":run_sksllex",
       "//third_party/externals/spirv-tools:spvtools",
       "//third_party/externals/spirv-tools:spvtools_val",
+      "//third_party/spirv-cross:spirv_cross",
     ]
   }
 
@@ -951,7 +953,10 @@ optional("gpu") {
   }
 
   if (skia_use_direct3d) {
-    public_defines += [ "SK_DIRECT3D" ]
+    public_defines += [
+      "SK_DIRECT3D",
+      "SK_ENABLE_SPIRV_CROSS",
+    ]
     deps += [
       "//third_party/d3d12allocator",
       "//third_party/spirv-cross:spirv_cross",

src/sksl/SkSLCompiler.cpp

@@ -675,13 +675,28 @@ bool Compiler::toGLSL(Program& program, String* out) {
     return result;
 }
 
+bool Compiler::toHLSL(Program& program, OutputStream& out) {
+    TRACE_EVENT0("skia.shaders", "SkSL::Compiler::toHLSL");
+    String hlsl;
+    if (!this->toHLSL(program, &hlsl)) {
+        return false;
+    }
+    out.writeString(hlsl);
+    return true;
+}
+
 bool Compiler::toHLSL(Program& program, String* out) {
     String spirv;
     if (!this->toSPIRV(program, &spirv)) {
         return false;
     }
 
-    return SPIRVtoHLSL(spirv, out);
+    if (!SPIRVtoHLSL(spirv, out)) {
+        fErrorText += "HLSL cross-compilation not enabled";
+        return false;
+    }
+
+    return true;
 }
 
 bool Compiler::toMetal(Program& program, OutputStream& out) {

src/sksl/SkSLCompiler.h

@@ -152,6 +152,8 @@ public:
 
     bool toGLSL(Program& program, String* out);
 
+    bool toHLSL(Program& program, OutputStream& out);
+
     bool toHLSL(Program& program, String* out);
 
     bool toMetal(Program& program, OutputStream& out);

src/sksl/SkSLMain.cpp

@@ -394,6 +394,11 @@ ResultCode processCommand(std::vector<SkSL::String>& args) {
                 [](SkSL::Compiler& compiler, SkSL::Program& program, SkSL::OutputStream& out) {
                     return compiler.toMetal(program, out);
                 });
+    } else if (outputPath.ends_with(".hlsl")) {
+        return compileProgram(
+                [](SkSL::Compiler& compiler, SkSL::Program& program, SkSL::OutputStream& out) {
+                    return compiler.toHLSL(program, out);
+                });
     } else if (outputPath.ends_with(".skvm")) {
         return compileProgramForSkVM(
                 [&](SkSL::Compiler&, SkSL::Program& program, SkSL::OutputStream& out) {
@@ -505,8 +510,8 @@ ResultCode processCommand(std::vector<SkSL::String>& args) {
             return ResultCode::kOutputError;
         }
     } else {
-        printf("expected output path to end with one of: .glsl, .metal, .spirv, .asm.frag, .skvm, "
-               ".stage, .asm.vert (got '%s')\n", outputPath.c_str());
+        printf("expected output path to end with one of: .glsl, .metal, .hlsl, .spirv, .asm.frag, "
+               ".skvm, .stage, .asm.vert, .dehydrated.sksl (got '%s')\n", outputPath.c_str());
         return ResultCode::kConfigurationError;
     }
     return ResultCode::kSuccess;

src/sksl/codegen/SkSLSPIRVtoHLSL.cpp

@@ -7,7 +7,7 @@
 
 #include "src/sksl/codegen/SkSLSPIRVtoHLSL.h"
 
-#if defined(SK_DIRECT3D)
+#if defined(SK_ENABLE_SPIRV_CROSS)
 
 #include "third_party/externals/spirv-cross/spirv_hlsl.hpp"