[llvm] [JITLink] Fix symbol transfer when splitting blocks (PR #225735)

[via llvm-commits]

https://github.com/maksimra updated https://github.com/llvm/llvm-project/pull/225735

>From 9f71e9923294460582cb338fa833c3b2ccd60fbf Mon Sep 17 00:00:00 2001
From: Maksim <rachinskii.mv at phystech.edu>
Date: Wed, 23 Sep 2026 13:09:21 +0300
Subject: [PATCH] [JITLink] Fix symbol transfer when splitting blocks

splitBlock method truncates the original block before transferring symbols. For symbols assigned to a later child, setting the new offset while the symbol still refers to the truncated block can trigger the offset range assertion. Preserve the absolute address, move the symbol to its destination block, and then derive the new block-relative offset.
---
 llvm/lib/ExecutionEngine/JITLink/JITLink.cpp  |  3 ++-
 .../JITLink/LinkGraphTests.cpp                | 22 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp b/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp
index 329414a5e12755..0236e274a05ee6 100644
--- a/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp
@@ -216,8 +216,9 @@ std::vector<Block *> LinkGraph::splitBlockImpl(std::vector<Block *> Blocks,
     }
 
     auto TransferSymbol = [](Symbol &Sym, Block &B) {
-      Sym.setOffset(Sym.getAddress() - B.getAddress());
+      const auto SymAddress = Sym.getAddress();
       Sym.setBlock(B);
+      Sym.setOffset(SymAddress - B.getAddress());
       if (Sym.getSize() > B.getSize())
         Sym.setSize(B.getSize() - Sym.getOffset());
     };
diff --git a/llvm/unittests/ExecutionEngine/JITLink/LinkGraphTests.cpp b/llvm/unittests/ExecutionEngine/JITLink/LinkGraphTests.cpp
index c7608734935282..c8ab7df0b1f4b2 100644
--- a/llvm/unittests/ExecutionEngine/JITLink/LinkGraphTests.cpp
+++ b/llvm/unittests/ExecutionEngine/JITLink/LinkGraphTests.cpp
@@ -833,6 +833,28 @@ TEST(LinkGraphTest, SplitBlock) {
     EXPECT_EQ(B3.edges().begin()->getOffset(), 0U);
 }
 
+TEST(LinkGraphTest, SplitBlockPreservesLaterSymbolAddress) {
+  LinkGraph G("foo", std::make_shared<orc::SymbolStringPool>(),
+              Triple("x86_64-apple-darwin"), SubtargetFeatures(),
+              getGenericEdgeKindName);
+  auto &Sec =
+      G.createSection("__data", orc::MemProt::Read | orc::MemProt::Write);
+
+  orc::ExecutorAddr BlockAddr(0x1000);
+  auto &B = G.createContentBlock(Sec, BlockContent, BlockAddr, 1, 0);
+  auto &S = G.addDefinedSymbol(B, 15, "S", 1, Linkage::Strong, Scope::Default,
+                               false, false);
+  const orc::ExecutorAddr SymbolAddr = S.getAddress();
+
+  auto Blocks = G.splitBlock(B, ArrayRef<int>({4, 8}));
+
+  ASSERT_EQ(Blocks.size(), 3U);
+  EXPECT_EQ(&S.getBlock(), Blocks[2]);
+  EXPECT_EQ(S.getOffset(), 7U);
+  EXPECT_EQ(S.getAddress(), SymbolAddr);
+  EXPECT_EQ(S.getSize(), 1U);
+}
+
 TEST(LinkGraphTest, GraphAllocationMethods) {
   LinkGraph G("foo", std::make_shared<orc::SymbolStringPool>(),
               Triple("x86_64-apple-darwin"), SubtargetFeatures(),