[mlir][spirv] Allow disabling control flow structurization (llvm#140561)

Currently some control flow patterns cannot be structurized into
existing SPIR-V MLIR constructs, e.g., conditional early exits (break).
Since the support for early exit cannot be currently added
(llvm#138688 (review))
this patch enables structurizer to be disabled to keep
the control flow unstructurized. By default, the control flow is
structurized.

Author: IgWod-IMG

mlir/include/mlir/Target/SPIRV/Deserialization.h

@@ -23,12 +23,19 @@ class MLIRContext;
 namespace spirv {
 class ModuleOp;
 
+struct DeserializationOptions {
+  // Whether to structurize control flow into `spirv.mlir.selection` and
+  // `spirv.mlir.loop`.
+  bool enableControlFlowStructurization = true;
+};
+
 /// Deserializes the given SPIR-V `binary` module and creates a MLIR ModuleOp
 /// in the given `context`. Returns the ModuleOp on success; otherwise, reports
 /// errors to the error handler registered with `context` and returns a null
 /// module.
-OwningOpRef<spirv::ModuleOp> deserialize(ArrayRef<uint32_t> binary,
-                                         MLIRContext *context);
+OwningOpRef<spirv::ModuleOp>
+deserialize(ArrayRef<uint32_t> binary, MLIRContext *context,
+            const DeserializationOptions &options = {});
 
 } // namespace spirv
 } // namespace mlir

mlir/lib/Target/SPIRV/Deserialization/Deserialization.cpp

@@ -12,9 +12,10 @@
 
 using namespace mlir;
 
-OwningOpRef<spirv::ModuleOp> spirv::deserialize(ArrayRef<uint32_t> binary,
-                                                MLIRContext *context) {
-  Deserializer deserializer(binary, context);
+OwningOpRef<spirv::ModuleOp>
+spirv::deserialize(ArrayRef<uint32_t> binary, MLIRContext *context,
+                   const DeserializationOptions &options) {
+  Deserializer deserializer(binary, context, options);
 
   if (failed(deserializer.deserialize()))
     return nullptr;

mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp

@@ -49,9 +49,10 @@ static inline bool isFnEntryBlock(Block *block) {
 //===----------------------------------------------------------------------===//
 
 spirv::Deserializer::Deserializer(ArrayRef<uint32_t> binary,
-                                  MLIRContext *context)
+                                  MLIRContext *context,
+                                  const spirv::DeserializationOptions &options)
     : binary(binary), context(context), unknownLoc(UnknownLoc::get(context)),
-      module(createModuleOp()), opBuilder(module->getRegion())
+      module(createModuleOp()), opBuilder(module->getRegion()), options(options)
 #ifndef NDEBUG
       ,
       logger(llvm::dbgs())
@@ -2361,6 +2362,16 @@ LogicalResult spirv::Deserializer::splitConditionalBlocks() {
 }
 
 LogicalResult spirv::Deserializer::structurizeControlFlow() {
+  if (!options.enableControlFlowStructurization) {
+    LLVM_DEBUG(
+        {
+          logger.startLine()
+              << "//----- [cf] skip structurizing control flow -----//\n";
+          logger.indent();
+        });
+    return success();
+  }
+
   LLVM_DEBUG({
     logger.startLine()
         << "//----- [cf] start structurizing control flow -----//\n";

mlir/lib/Target/SPIRV/Deserialization/Deserializer.h

@@ -16,6 +16,7 @@
 #include "mlir/Dialect/SPIRV/IR/SPIRVEnums.h"
 #include "mlir/Dialect/SPIRV/IR/SPIRVOps.h"
 #include "mlir/IR/Builders.h"
+#include "mlir/Target/SPIRV/Deserialization.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/StringRef.h"
@@ -121,7 +122,8 @@ class Deserializer {
 public:
   /// Creates a deserializer for the given SPIR-V `binary` module.
   /// The SPIR-V ModuleOp will be created into `context.
-  explicit Deserializer(ArrayRef<uint32_t> binary, MLIRContext *context);
+  explicit Deserializer(ArrayRef<uint32_t> binary, MLIRContext *context,
+                        const DeserializationOptions &options);
 
   /// Deserializes the remembered SPIR-V binary module.
   LogicalResult deserialize();
@@ -622,6 +624,9 @@ class Deserializer {
   /// A list of all structs which have unresolved member types.
   SmallVector<DeferredStructTypeInfo, 0> deferredStructTypesInfos;
 
+  /// Deserialization options.
+  DeserializationOptions options;
+
 #ifndef NDEBUG
   /// A logger used to emit information during the deserialzation process.
   llvm::ScopedPrinter logger;

mlir/lib/Target/SPIRV/TranslateRegistration.cpp

@@ -37,7 +37,8 @@ using namespace mlir;
 // Deserializes the SPIR-V binary module stored in the file named as
 // `inputFilename` and returns a module containing the SPIR-V module.
 static OwningOpRef<Operation *>
-deserializeModule(const llvm::MemoryBuffer *input, MLIRContext *context) {
+deserializeModule(const llvm::MemoryBuffer *input, MLIRContext *context,
+                  const spirv::DeserializationOptions &options) {
   context->loadDialect<spirv::SPIRVDialect>();
 
   // Make sure the input stream can be treated as a stream of SPIR-V words
@@ -51,17 +52,26 @@ deserializeModule(const llvm::MemoryBuffer *input, MLIRContext *context) {
 
   auto binary = llvm::ArrayRef(reinterpret_cast<const uint32_t *>(start),
                                size / sizeof(uint32_t));
-  return spirv::deserialize(binary, context);
+  return spirv::deserialize(binary, context, options);
 }
 
 namespace mlir {
 void registerFromSPIRVTranslation() {
+  static llvm::cl::opt<bool> enableControlFlowStructurization(
+      "spirv-structurize-control-flow",
+      llvm::cl::desc(
+          "Enable control flow structurization into `spirv.mlir.selection` and "
+          "`spirv.mlir.loop`. This may need to be disabled to support "
+          "deserialization of early exits (see #138688)"),
+      llvm::cl::init(true));
+
   TranslateToMLIRRegistration fromBinary(
       "deserialize-spirv", "deserializes the SPIR-V module",
       [](llvm::SourceMgr &sourceMgr, MLIRContext *context) {
         assert(sourceMgr.getNumBuffers() == 1 && "expected one buffer");
         return deserializeModule(
-            sourceMgr.getMemoryBuffer(sourceMgr.getMainFileID()), context);
+            sourceMgr.getMemoryBuffer(sourceMgr.getMainFileID()), context,
+            {enableControlFlowStructurization});
       });
 }
 } // namespace mlir