[llvm-branch-commits] [llvm] release/19.x: [RemoveDIs] Simplify spliceDebugInfo, fixing splice-to-end edge case (#105670) (PR #106690)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-ir

Author: None (llvmbot)

<details>
<summary>Changes</summary>

Backport f5815534d180c544bffd46f09c28b6fc334260fb

Requested by: @<!-- -->OCHyams

---
Full diff: https://github.com/llvm/llvm-project/pull/106690.diff


2 Files Affected:

- (modified) llvm/lib/IR/BasicBlock.cpp (+10-14) 
- (modified) llvm/unittests/IR/BasicBlockDbgInfoTest.cpp (+2-2) 


``````````diff
diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
index bf19934da047c4..0a9498f051cb59 100644
--- a/llvm/lib/IR/BasicBlock.cpp
+++ b/llvm/lib/IR/BasicBlock.cpp
@@ -961,9 +961,13 @@ void BasicBlock::spliceDebugInfoImpl(BasicBlock::iterator Dest, BasicBlock *Src,
   // Detach the marker at Dest -- this lets us move the "====" DbgRecords
   // around.
   DbgMarker *DestMarker = nullptr;
-  if (Dest != end()) {
-    if ((DestMarker = getMarker(Dest)))
+  if ((DestMarker = getMarker(Dest))) {
+    if (Dest == end()) {
+      assert(DestMarker == getTrailingDbgRecords());
+      deleteTrailingDbgRecords();
+    } else {
       DestMarker->removeFromParent();
+    }
   }
 
   // If we're moving the tail range of DbgRecords (":::"), absorb them into the
@@ -1005,22 +1009,14 @@ void BasicBlock::spliceDebugInfoImpl(BasicBlock::iterator Dest, BasicBlock *Src,
     } else {
       // Insert them right at the start of the range we moved, ahead of First
       // and the "++++" DbgRecords.
+      // This also covers the rare circumstance where we insert at end(), and we
+      // did not generate the iterator with begin() / getFirstInsertionPt(),
+      // meaning any trailing debug-info at the end of the block would
+      // "normally" have been pushed in front of "First". We move it there now.
       DbgMarker *FirstMarker = createMarker(First);
       FirstMarker->absorbDebugValues(*DestMarker, true);
     }
     DestMarker->eraseFromParent();
-  } else if (Dest == end() && !InsertAtHead) {
-    // In the rare circumstance where we insert at end(), and we did not
-    // generate the iterator with begin() / getFirstInsertionPt(), it means
-    // any trailing debug-info at the end of the block would "normally" have
-    // been pushed in front of "First". Move it there now.
-    DbgMarker *TrailingDbgRecords = getTrailingDbgRecords();
-    if (TrailingDbgRecords) {
-      DbgMarker *FirstMarker = createMarker(First);
-      FirstMarker->absorbDebugValues(*TrailingDbgRecords, true);
-      TrailingDbgRecords->eraseFromParent();
-      deleteTrailingDbgRecords();
-    }
   }
 }
 
diff --git a/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp b/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp
index 91a0745a0cc76e..835780e63aaf4f 100644
--- a/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp
+++ b/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp
@@ -141,11 +141,11 @@ TEST(BasicBlockDbgInfoTest, SplitBasicBlockBefore) {
   Function *F = M->getFunction("func");
 
   BasicBlock &BB = F->getEntryBlock();
-  auto I = std::prev(BB.end(), 2);
+  auto I = std::prev(BB.end(), 2); // store i32 2, ptr %1.
   BB.splitBasicBlockBefore(I, "before");
 
   BasicBlock &BBBefore = F->getEntryBlock();
-  auto I2 = std::prev(BBBefore.end(), 2);
+  auto I2 = std::prev(BBBefore.end()); // br label %1 (new).
   ASSERT_TRUE(I2->hasDbgRecords());
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/106690