[mlir][spirv] Allow disabling control flow structurization

[IgWod-IMG]

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 (#138688 (review) in see #138688) this patch enables structurizer to be disabled to keep the control flow unstructurized. By default, the control flow is structurized.

[llvmbot]

@llvm/pr-subscribers-mlir-spirv

@llvm/pr-subscribers-mlir

Author: Igor Wodiany (IgWod-IMG)

Changes

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 (#138688 (review) in see #138688) this patch enables structurizer to be disabled to keep the control flow unstructurized. By default, the control flow is structurized.

---

Full diff: https://github.com/llvm/llvm-project/pull/140561.diff

5 Files Affected:

• (modified) mlir/include/mlir/Target/SPIRV/Deserialization.h (+3-2)
• (modified) mlir/lib/Target/SPIRV/Deserialization/Deserialization.cpp (+4-3)
• (modified) mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp (+14-2)
• (modified) mlir/lib/Target/SPIRV/Deserialization/Deserializer.h (+7-1)
• (modified) mlir/lib/Target/SPIRV/TranslateRegistration.cpp (+11-3)

diff --git a/mlir/include/mlir/Target/SPIRV/Deserialization.h b/mlir/include/mlir/Target/SPIRV/Deserialization.h
index a346a7fd1e5f7..adff26298c4cc 100644
--- a/mlir/include/mlir/Target/SPIRV/Deserialization.h
+++ b/mlir/include/mlir/Target/SPIRV/Deserialization.h
@@ -27,8 +27,9 @@ class 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,
+            bool enableControlFlowStructurization = true);
 
 } // namespace spirv
 } // namespace mlir
diff --git a/mlir/lib/Target/SPIRV/Deserialization/Deserialization.cpp b/mlir/lib/Target/SPIRV/Deserialization/Deserialization.cpp
index 7bb8762660599..11a9de91060a8 100644
--- a/mlir/lib/Target/SPIRV/Deserialization/Deserialization.cpp
+++ b/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,
+                   bool enableControlFlowStructurization) {
+  Deserializer deserializer(binary, context, enableControlFlowStructurization);
 
   if (failed(deserializer.deserialize()))
     return nullptr;
diff --git a/mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp b/mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp
index 7afd6e9b25b77..1aa647485496d 100644
--- a/mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp
+++ b/mlir/lib/Target/SPIRV/Deserialization/Deserializer.cpp
@@ -49,9 +49,11 @@ static inline bool isFnEntryBlock(Block *block) {
 //===----------------------------------------------------------------------===//
 
 spirv::Deserializer::Deserializer(ArrayRef<uint32_t> binary,
-                                  MLIRContext *context)
+                                  MLIRContext *context,
+                                  bool enableControlFlowStructurization)
     : binary(binary), context(context), unknownLoc(UnknownLoc::get(context)),
-      module(createModuleOp()), opBuilder(module->getRegion())
+      module(createModuleOp()), opBuilder(module->getRegion()),
+      enableControlFlowStructurization(enableControlFlowStructurization)
 #ifndef NDEBUG
       ,
       logger(llvm::dbgs())
@@ -2361,6 +2363,16 @@ LogicalResult spirv::Deserializer::splitConditionalBlocks() {
 }
 
 LogicalResult spirv::Deserializer::structurizeControlFlow() {
+  if (!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";
diff --git a/mlir/lib/Target/SPIRV/Deserialization/Deserializer.h b/mlir/lib/Target/SPIRV/Deserialization/Deserializer.h
index bcc78e3e6508d..c1df77ba7b647 100644
--- a/mlir/lib/Target/SPIRV/Deserialization/Deserializer.h
+++ b/mlir/lib/Target/SPIRV/Deserialization/Deserializer.h
@@ -121,7 +121,10 @@ 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);
+  /// `enableControlFlowStructurization` is used to enable control flow
+  /// structurization.
+  explicit Deserializer(ArrayRef<uint32_t> binary, MLIRContext *context,
+                        bool enableControlFlowStructurization);
 
   /// Deserializes the remembered SPIR-V binary module.
   LogicalResult deserialize();
@@ -622,6 +625,9 @@ class Deserializer {
   /// A list of all structs which have unresolved member types.
   SmallVector<DeferredStructTypeInfo, 0> deferredStructTypesInfos;
 
+  /// A flag to enable or disable structurizer
+  bool enableControlFlowStructurization;
+
 #ifndef NDEBUG
   /// A logger used to emit information during the deserialzation process.
   llvm::ScopedPrinter logger;
diff --git a/mlir/lib/Target/SPIRV/TranslateRegistration.cpp b/mlir/lib/Target/SPIRV/TranslateRegistration.cpp
index ff34f02d07b73..90e5b684607be 100644
--- a/mlir/lib/Target/SPIRV/TranslateRegistration.cpp
+++ b/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,
+                  bool enableControlFlowStructurization) {
   context->loadDialect<spirv::SPIRVDialect>();
 
   // Make sure the input stream can be treated as a stream of SPIR-V words
@@ -51,17 +52,24 @@ 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, enableControlFlowStructurization);
 }
 
 namespace mlir {
 void registerFromSPIRVTranslation() {
+  static llvm::cl::opt<bool> noControlFlowStructurization(
+      "spirv-no-control-flow-structurization",
+      llvm::cl::desc("Disable control flow structurization to enable "
+                     "deserialization of early exits (see #138688)"),
+      llvm::cl::init(false));
+
   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,
+            !noControlFlowStructurization);
       });
 }
 } // namespace mlir