[Mlir-commits] [mlir] [mlir][gpu] Introduce `gpu.dynamic_shared_memory` Op (PR #71546)

[Markus Böck]

================
@@ -554,6 +555,95 @@ static IntegerAttr wrapNumericMemorySpace(MLIRContext *ctx, unsigned space) {
   return IntegerAttr::get(IntegerType::get(ctx, 64), space);
 }
 
+/// Generates a symbol with 0-sized array type for dynamic shared memory usage,
+/// or uses existing symbol.
+LLVM::GlobalOp
+getDynamicSharedMemorySymbol(ConversionPatternRewriter &rewriter,
+                             gpu::DynamicSharedMemoryOp op,
+                             const LLVMTypeConverter *typeConverter,
+                             MemRefType memrefType, unsigned alignmentBit) {
+  std::optional<LLVM::GlobalOp> existingGlobalOp;
+
+  LLVM::LLVMFuncOp funcOp = op->getParentOfType<LLVM::LLVMFuncOp>();
+  assert(funcOp && "cannot find llvm.func op");
+
+  gpu::GPUModuleOp moduleOp = funcOp->getParentOfType<gpu::GPUModuleOp>();
+  assert(moduleOp && "cannot find gpu.module op");
+
+  // Use already generated global op if it exists
+  int index = 0;
+  std::string prefix = llvm::formatv("__shmem_{0}", funcOp.getSymName());
+  moduleOp->walk([&](LLVM::GlobalOp globalOp) {
+    if (auto arrayType = dyn_cast<LLVM::LLVMArrayType>(globalOp.getType())) {
+      if (arrayType.getNumElements() == 0) {
+        existingGlobalOp = globalOp;
+        return WalkResult::interrupt();
+      }
+    }
+    if (globalOp.getSymName().startswith(prefix))
+      index++;
----------------
zero9178 wrote:

Your backtrace seems to indicate that you're creating the `mlir::SymbolTable` during pattern application in `matchAndRewrite`. Since the IR is not guaranteed to be a in a valid shape anymore at that point in time you're seeing that error.

I believe if you create the `mlir::SymbolTable` before application, either in the constructor of the pattern or passing it into the pattern, that it should circumvent this issue (as its internal map is initialized with the IR prior to any rewriting). This theoretically has its own issuses that should not be a problem here but I don't think we currently have the infrastructure to share symbol tabless between patterns, do we?

https://github.com/llvm/llvm-project/pull/71546