[Mlir-commits] [mlir] [mlir][acc] Erase empty kernel_environment ops during canonicalization (PR #166633)

[Razvan Lupusoru]

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@@ -1042,6 +1042,35 @@ struct RemoveConstantIfConditionWithRegion : public OpRewritePattern<OpTy> {
   }
 };
 
+/// Remove empty acc.kernel_environment operations. If the operation has wait
+/// operands, create a acc.wait operation to preserve synchronization.
+struct RemoveEmptyKernelEnvironment
+    : public OpRewritePattern<acc::KernelEnvironmentOp> {
+  using OpRewritePattern<acc::KernelEnvironmentOp>::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(acc::KernelEnvironmentOp op,
+                                PatternRewriter &rewriter) const override {
+    assert(op->getNumRegions() == 1 && "expected op to have one region");
+
+    Block &block = op.getRegion().front();
+    if (!block.empty())
+      return failure();
+
+    // Remove empty kernel environment
+    // preserve synchronization by creating acc.wait operation if needed
+    if (!op.getWaitOperands().empty())
----------------
razvanlupusoru wrote:

FWIW - it looks like to me that acc.wait would only support a subset of functionality from acc.kernel_environment - primarily due to not having support for device_type. So I think your approach would be one of:
- only handle waitOperands and waitOnly and avoid "canonicalizing/folding" the empty kernels_environment region
- add the needed support to acc.wait

https://github.com/llvm/llvm-project/pull/166633