[mlir] Dialect Conversion: Fix expensive pattern check in no-rollback mode

[timnoack]

Fixes a bug causing every conversion to fail fatally with "expected pattern to replace the root operation or modify it in place" when MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS is enabled and pattern rollback is disabled.

When allowPatternRollback is disabled, the rewriter does not keep track of the rewrites it performs and can therefore not use that list to check whether the root op was replaced or updated in place.

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[llvmbot]

@llvm/pr-subscribers-mlir

@llvm/pr-subscribers-mlir-core

Author: Tim Noack (timnoack)

Changes

Fixes a bug causing every conversion to fail fatally with "expected pattern to replace the root operation or modify it in place" when MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS is enabled and pattern rollback is disabled.

When allowPatternRollback is disabled, the rewriter does not keep track of the rewrites it performs and can therefore not use that list to check whether the root op was replaced or updated in place.

---

Full diff: https://github.com/llvm/llvm-project/pull/166576.diff

1 Files Affected:

• (modified) mlir/lib/Transforms/Utils/DialectConversion.cpp (+13-11)

diff --git a/mlir/lib/Transforms/Utils/DialectConversion.cpp b/mlir/lib/Transforms/Utils/DialectConversion.cpp
index 2fe06970eb568..424349b555228 100644
--- a/mlir/lib/Transforms/Utils/DialectConversion.cpp
+++ b/mlir/lib/Transforms/Utils/DialectConversion.cpp
@@ -2804,17 +2804,19 @@ LogicalResult OperationLegalizer::legalizePatternResult(
   assert(impl.pendingRootUpdates.empty() && "dangling root updates");
 
 #if MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
-  // Check that the root was either replaced or updated in place.
-  auto newRewrites = llvm::drop_begin(impl.rewrites, curState.numRewrites);
-  auto replacedRoot = [&] {
-    return hasRewrite<ReplaceOperationRewrite>(newRewrites, op);
-  };
-  auto updatedRootInPlace = [&] {
-    return hasRewrite<ModifyOperationRewrite>(newRewrites, op);
-  };
-  if (!replacedRoot() && !updatedRootInPlace())
-    llvm::report_fatal_error(
-        "expected pattern to replace the root operation or modify it in place");
+  if (impl.config.allowPatternRollback) {
+    // Check that the root was either replaced or updated in place.
+    auto newRewrites = llvm::drop_begin(impl.rewrites, curState.numRewrites);
+    auto replacedRoot = [&] {
+      return hasRewrite<ReplaceOperationRewrite>(newRewrites, op);
+    };
+    auto updatedRootInPlace = [&] {
+      return hasRewrite<ModifyOperationRewrite>(newRewrites, op);
+    };
+    if (!replacedRoot() && !updatedRootInPlace())
+      llvm::report_fatal_error("expected pattern to replace the root operation "
+                               "or modify it in place");
+  }
 #endif // MLIR_ENABLE_EXPENSIVE_PATTERN_API_CHECKS
 
   // Legalize each of the actions registered during application.

[timnoack]

@matthias-springer just wanted to share my patch. Feel free to reject it if there is a different way to perform that check in no-rollback mode.

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