[Mlir-commits] [mlir] [mlir][Transforms] Fix crash in dialect conversion (PR #82783)

[Matthias Springer]

https://github.com/matthias-springer created https://github.com/llvm/llvm-project/pull/82783

This is a follow-up to #82333. It possible that the target block of a `BlockTypeConversionRewrite` is detached, so the `MLIRContext` cannot be taken from the block.

>From a02164d6d0fe78f9825f84a80111fea7510d543c Mon Sep 17 00:00:00 2001
From: Matthias Springer <springerm at google.com>
Date: Fri, 23 Feb 2024 16:12:11 +0000
Subject: [PATCH] [mlir][Transforms] Fix crash in dialect conversion

This is a follow-up to #82333. It possible that the target block of a
`BlockTypeConversionRewrite` is detached, so the `MLIRContext` cannot be
taken from the block.
---
 mlir/lib/Transforms/Utils/DialectConversion.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mlir/lib/Transforms/Utils/DialectConversion.cpp b/mlir/lib/Transforms/Utils/DialectConversion.cpp
index d015bd52901233..843eb5ef9bad47 100644
--- a/mlir/lib/Transforms/Utils/DialectConversion.cpp
+++ b/mlir/lib/Transforms/Utils/DialectConversion.cpp
@@ -1034,15 +1034,15 @@ void BlockTypeConversionRewrite::rollback() {
 
 LogicalResult BlockTypeConversionRewrite::materializeLiveConversions(
     function_ref<Operation *(Value)> findLiveUser) {
-  auto builder = OpBuilder::atBlockBegin(block, /*listener=*/&rewriterImpl);
-
   // Process the remapping for each of the original arguments.
   for (auto it : llvm::enumerate(origBlock->getArguments())) {
-    OpBuilder::InsertionGuard g(builder);
+    BlockArgument origArg = it.value();
+    // Note: `block` may be detached, so OpBuilder::atBlockBegin cannot be used.
+    OpBuilder builder(it.value().getContext(), /*listener=*/&rewriterImpl);
+    builder.setInsertionPointToStart(block);
 
     // If the type of this argument changed and the argument is still live, we
     // need to materialize a conversion.
-    BlockArgument origArg = it.value();
     if (rewriterImpl.mapping.lookupOrNull(origArg, origArg.getType()))
       continue;
     Operation *liveUser = findLiveUser(origArg);