[mlir][spirv] Handle all zero-element memref types (#73351)

Bail out of type conversion instead of crashing.

Fixes: #73289

Author: kuhar

mlir/lib/Dialect/SPIRV/Transforms/SPIRVConversion.cpp

@@ -469,6 +469,12 @@ static Type convertBoolMemrefType(const spirv::TargetEnv &targetEnv,
     return wrapInStructAndGetPointer(arrayType, storageClass);
   }
 
+  if (type.getNumElements() == 0) {
+    LLVM_DEBUG(llvm::dbgs()
+               << type << " illegal: zero-element memrefs are not supported\n");
+    return nullptr;
+  }
+
   int64_t memrefSize = llvm::divideCeil(type.getNumElements() * numBoolBits, 8);
   int64_t arrayElemCount = llvm::divideCeil(memrefSize, *arrayElemSize);
   int64_t stride = needsExplicitLayout(storageClass) ? *arrayElemSize : 0;
@@ -500,6 +506,12 @@ static Type convertSubByteMemrefType(const spirv::TargetEnv &targetEnv,
     return wrapInStructAndGetPointer(arrayType, storageClass);
   }
 
+  if (type.getNumElements() == 0) {
+    LLVM_DEBUG(llvm::dbgs()
+               << type << " illegal: zero-element memrefs are not supported\n");
+    return nullptr;
+  }
+
   int64_t memrefSize =
       llvm::divideCeil(type.getNumElements() * elementType.getWidth(), 8);
   int64_t arrayElemCount = llvm::divideCeil(memrefSize, arrayElemSize);

mlir/test/Conversion/MemRefToSPIRV/alloc.mlir

@@ -187,6 +187,8 @@ module attributes {
 {
   func.func @zero_size() {
     %0 = memref.alloc() : memref<0xf32, #spirv.storage_class<Workgroup>>
+    %1 = memref.alloc() : memref<0xi1, #spirv.storage_class<Workgroup>>
+    %2 = memref.alloc() : memref<0xi4, #spirv.storage_class<Workgroup>>
     return
   }
 }