[mlir][acc] Erase empty kernel_environment ops during canonicalization #166633
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@llvm/pr-subscribers-mlir @llvm/pr-subscribers-mlir-openacc Author: Vijay Kandiah (VijayKandiah) ChangesThis change removes empty In cases of empty Full diff: https://github.com/llvm/llvm-project/pull/166633.diff 3 Files Affected:
diff --git a/mlir/include/mlir/Dialect/OpenACC/OpenACCOps.td b/mlir/include/mlir/Dialect/OpenACC/OpenACCOps.td
index c689b7e46ea9e..5b89f741e296d 100644
--- a/mlir/include/mlir/Dialect/OpenACC/OpenACCOps.td
+++ b/mlir/include/mlir/Dialect/OpenACC/OpenACCOps.td
@@ -2184,6 +2184,8 @@ def OpenACC_KernelEnvironmentOp : OpenACC_Op<"kernel_environment",
)
$region attr-dict
}];
+
+ let hasCanonicalizer = 1;
}
//===----------------------------------------------------------------------===//
diff --git a/mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp b/mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp
index b2f1d840f3bca..fa303ed675daf 100644
--- a/mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp
+++ b/mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp
@@ -1042,6 +1042,37 @@ 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()) {
+ rewriter.replaceOpWithNewOp<acc::WaitOp>(
+ op,
+ /*waitOperands=*/op.getWaitOperands(),
+ /*asyncOperand=*/Value(),
+ /*waitDevnum=*/Value(),
+ /*async=*/nullptr,
+ /*ifCond=*/Value());
+ } else
+ rewriter.eraseOp(op);
+
+ return success();
+ }
+};
+
//===----------------------------------------------------------------------===//
// Recipe Region Helpers
//===----------------------------------------------------------------------===//
@@ -2690,6 +2721,15 @@ void acc::HostDataOp::getCanonicalizationPatterns(RewritePatternSet &results,
results.add<RemoveConstantIfConditionWithRegion<HostDataOp>>(context);
}
+//===----------------------------------------------------------------------===//
+// KernelEnvironmentOp
+//===----------------------------------------------------------------------===//
+
+void acc::KernelEnvironmentOp::getCanonicalizationPatterns(
+ RewritePatternSet &results, MLIRContext *context) {
+ results.add<RemoveEmptyKernelEnvironment>(context);
+}
+
//===----------------------------------------------------------------------===//
// LoopOp
//===----------------------------------------------------------------------===//
diff --git a/mlir/test/Dialect/OpenACC/canonicalize.mlir b/mlir/test/Dialect/OpenACC/canonicalize.mlir
index fdc8e6b5cae6e..6d600a386f926 100644
--- a/mlir/test/Dialect/OpenACC/canonicalize.mlir
+++ b/mlir/test/Dialect/OpenACC/canonicalize.mlir
@@ -219,3 +219,29 @@ func.func @update_unnecessary_computations(%x: memref<i32>) {
// CHECK-LABEL: func.func @update_unnecessary_computations
// CHECK-NOT: acc.atomic.update
// CHECK: acc.atomic.write
+
+// -----
+
+func.func @remove_empty_kernel_environment() {
+ acc.kernel_environment {
+ }
+ return
+}
+
+// CHECK-LABEL: func.func @remove_empty_kernel_environment
+// CHECK-NOT: acc.kernel_environment
+// CHECK: return
+
+// -----
+
+func.func @kernel_environment_with_wait(%q1: i32, %q2: i32) {
+ acc.kernel_environment wait({%q1 : i32, %q2 : i32}) {
+ }
+ return
+}
+
+// CHECK-LABEL: func.func @kernel_environment_with_wait
+// CHECK-SAME: ([[Q1:%.*]]: i32, [[Q2:%.*]]: i32)
+// CHECK-NOT: acc.kernel_environment
+// CHECK: acc.wait([[Q1]], [[Q2]] : i32, i32)
+// CHECK: return
|
clementval
approved these changes
Nov 5, 2025
clementval
reviewed
Nov 5, 2025
|
✅ With the latest revision this PR passed the C/C++ code formatter. |
razvanlupusoru
requested changes
Nov 5, 2025
Collaborator
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/129/builds/32615 Here is the relevant piece of the build log for the reference |
vinay-deshmukh
pushed a commit
to vinay-deshmukh/llvm-project
that referenced
this pull request
Nov 8, 2025
llvm#166633) This change removes empty `acc.kernel_environment` operations during canonicalization. This could happen when the acc compute construct inside the `acc.kernel_environment` is optimized away in cases such as when only private variables are being written to in the loop. In cases of empty `acc.kernel_environment` ops with waitOperands, we still remove the empty `acc.kernel_environment`, but also create an `acc.wait` operation to take those wait operands to preserve synchronization behavior.
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This change removes empty
acc.kernel_environmentoperations during canonicalization. This could happen when the acc compute construct inside theacc.kernel_environmentis optimized away in cases such as when only private variables are being written to in the loop.In cases of empty
acc.kernel_environmentops with waitOperands, we still remove the emptyacc.kernel_environment, but also create anacc.waitoperation to take those wait operands to preserve synchronization behavior.