Add support for SPV_INTEL_function_variants (KhronosGroup#6211)

Add support for SPV_INTEL_function_variants

* Adds validation support for the SPV_INTEL_function_variants extension.  
See https://github.com/intel/llvm/blob/sycl/sycl/doc/design/spirv-extensions/SPV_INTEL_function_variants.asciidoc 
*  Augments the linker to be able to produce multitarget modules described in the extension spec. Details of how it works are documented in fnvar.h.

The values to pass to OpSpecConstantArchitectureINTEL and OpSpecConstantTargetINTEL can be determined from targets registry.

Co-authored-by: David Neto <[email protected]>

Author: jzadnik

BUILD.bazel

@@ -202,7 +202,7 @@ cc_library(
 cc_library(
     name = "spirv_tools_link",
     srcs = glob(["source/link/*.cpp"]),
-    hdrs = ["include/spirv-tools/linker.hpp"],
+    hdrs = ["include/spirv-tools/linker.hpp", "source/link/fnvar.h"],
     copts = COMMON_COPTS,
     linkstatic = 1,
     visibility = ["//visibility:public"],

include/spirv-tools/libspirv.h

@@ -80,6 +80,8 @@ typedef enum spv_result_t {
   SPV_ERROR_INVALID_DATA = -14,  // Indicates data rules validation failure.
   SPV_ERROR_MISSING_EXTENSION = -15,
   SPV_ERROR_WRONG_VERSION = -16,  // Indicates wrong SPIR-V version
+  SPV_ERROR_FNVAR =
+      -17,  // Error related to SPV_INTEL_function_variants extension
   SPV_FORCE_32_BIT_ENUM(spv_result_t)
 } spv_result_t;
 

include/spirv-tools/linker.hpp

@@ -67,12 +67,36 @@ class SPIRV_TOOLS_EXPORT LinkerOptions {
     allow_ptr_type_mismatch_ = allow_ptr_type_mismatch;
   }
 
+  std::string GetFnVarTargetsCsv() const { return fnvar_targets_csv_; }
+  void SetFnVarTargetsCsv(std::string fnvar_targets_csv) {
+    fnvar_targets_csv_ = fnvar_targets_csv;
+  }
+
+  std::string GetFnVarArchitecturesCsv() const {
+    return fnvar_architectures_csv_;
+  }
+  void SetFnVarArchitecturesCsv(std::string fnvar_architectures_csv) {
+    fnvar_architectures_csv_ = fnvar_architectures_csv;
+  }
+
+  bool GetHasFnVarCapabilities() const { return has_fnvar_capabilities_; }
+  void SetHasFnVarCapabilities(bool fnvar_capabilities) {
+    has_fnvar_capabilities_ = fnvar_capabilities;
+  }
+
+  std::vector<std::string> GetInFiles() const { return in_files_; }
+  void SetInFiles(std::vector<std::string> in_files) { in_files_ = in_files; }
+
  private:
   bool create_library_{false};
   bool verify_ids_{false};
   bool allow_partial_linkage_{false};
   bool use_highest_version_{false};
   bool allow_ptr_type_mismatch_{false};
+  std::string fnvar_targets_csv_{""};
+  std::string fnvar_architectures_csv_{""};
+  bool has_fnvar_capabilities_ = false;
+  std::vector<std::string> in_files_{{}};
 };
 
 // Links one or more SPIR-V modules into a new SPIR-V module. That is, combine

source/extensions.cpp

@@ -24,18 +24,24 @@
 namespace spvtools {
 
 std::string GetExtensionString(const spv_parsed_instruction_t* inst) {
-  if (inst->opcode != static_cast<uint16_t>(spv::Op::OpExtension)) {
+  if ((inst->opcode != static_cast<uint16_t>(spv::Op::OpExtension)) &&
+      (inst->opcode !=
+       static_cast<uint16_t>(spv::Op::OpConditionalExtensionINTEL))) {
     return "ERROR_not_op_extension";
   }
 
-  assert(inst->num_operands == 1);
+  const bool is_conditional =
+      inst->opcode ==
+      static_cast<uint16_t>(spv::Op::OpConditionalExtensionINTEL);
+  assert(inst->num_operands == (is_conditional ? 2 : 1));
+  const uint16_t op_i = is_conditional ? 1 : 0;
 
-  const auto& operand = inst->operands[0];
+  const auto& operand = inst->operands[op_i];
   assert(operand.type == SPV_OPERAND_TYPE_LITERAL_STRING);
   assert(inst->num_words > operand.offset);
   (void)operand; /* No unused variables in release builds. */
 
-  return spvDecodeLiteralStringOperand(*inst, 0);
+  return spvDecodeLiteralStringOperand(*inst, op_i);
 }
 
 std::string ExtensionSetToString(const ExtensionSet& extensions) {

source/fuzz/force_render_red.cpp

@@ -36,8 +36,11 @@ opt::Function* FindFragmentShaderEntryPoint(opt::IRContext* ir_context,
   // Check that this is a fragment shader
   bool found_capability_shader = false;
   for (auto& capability : ir_context->capabilities()) {
-    assert(capability.opcode() == spv::Op::OpCapability);
-    if (spv::Capability(capability.GetSingleWordInOperand(0)) ==
+    assert(capability.opcode() == spv::Op::OpCapability ||
+           capability.opcode() == spv::Op::OpConditionalCapabilityINTEL);
+    const uint32_t i_cap =
+        capability.opcode() == spv::Op::OpConditionalCapabilityINTEL ? 1 : 0;
+    if (spv::Capability(capability.GetSingleWordInOperand(i_cap)) ==
         spv::Capability::Shader) {
       found_capability_shader = true;
       break;

source/link/CMakeLists.txt

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 add_library(SPIRV-Tools-link ${SPIRV_TOOLS_LIBRARY_TYPE}
+  fnvar.cpp
   linker.cpp
 )