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

[Mehdi Amini]

================
@@ -554,6 +557,101 @@ 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) {
+  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");
+
+  uint64_t alignmentByte = alignmentBit / memrefType.getElementTypeBitWidth();
+
+  LLVM::GlobalOp existingGlobalOp;
+  moduleOp->walk([&](LLVM::GlobalOp globalOp) {
+    if (auto arrayType = dyn_cast<LLVM::LLVMArrayType>(globalOp.getType())) {
+      if (arrayType.getNumElements() == 0 &&
+          globalOp.getAlignment().value_or(0) == alignmentByte) {
+        existingGlobalOp = globalOp;
+      }
+    }
+  });
+  if (existingGlobalOp)
+    return existingGlobalOp;
+
+  // Find unique name
+  int index = 0;
+  std::string symName, name = llvm::formatv("__shmem_{0}", funcOp.getSymName());
+  WalkResult walkResult;
+  do {
+    symName = llvm::formatv("{0}_{1}", name, index++);
+    walkResult = moduleOp->walk([&](LLVM::GlobalOp globalOp) {
+      if (globalOp.getSymName() == symName)
+        return WalkResult::interrupt();
+      return WalkResult::advance();
+    });
----------------
joker-eph wrote:

This is another prohibitively costly walk, please find another solution.

(we don't have a SymbolTable available by the way?)

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