[llvm-branch-commits] [llvm] release/19.x: [RemoveDIs] Fix spliceDebugInfo splice-to-end edge case (#105671, #106723) (PR #106952)

[Orlando Cazalet-Hyams via llvm-branch-commits]

https://github.com/OCHyams created https://github.com/llvm/llvm-project/pull/106952

Please can we backport 43661a1214353ea1773a711f403f8d1118e9ca0f (and 7ffe67c17c524c2d3056c0721a33c7012dce3061) into the next dot release.

Replaces #106691 - this one includes a follow-up fix in 7ffe67c17c524c2d3056c0721a33c7012dce3061. I couldn't create two separate requests because it creates conflicts.

>From 70d00400165ee76199a1e4565fdebb6d84d2eec7 Mon Sep 17 00:00:00 2001
From: Orlando Cazalet-Hyams <orlando.hyams at sony.com>
Date: Thu, 29 Aug 2024 14:12:02 +0100
Subject: [PATCH 1/2] [RemoveDIs] Fix spliceDebugInfo splice-to-end edge case
 (#105671)

Fix #105571 which demonstrates an end() iterator dereference when
performing a non-empty splice to end() from a region that ends at
Src::end().

Rather than calling Instruction::adoptDbgRecords from Dest, create a marker
(which takes an iterator) and absorbDebugValues onto that. The "absorb" variant
doesn't clean up the source marker, which in this case we know is a trailing
marker, so we have to do that manually.

(cherry picked from commit 43661a1214353ea1773a711f403f8d1118e9ca0f)
---
 llvm/lib/IR/BasicBlock.cpp                  | 12 ++++-
 llvm/unittests/IR/BasicBlockDbgInfoTest.cpp | 54 +++++++++++++++++++++
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
index 0a9498f051cb59..46896d3cdf7d50 100644
--- a/llvm/lib/IR/BasicBlock.cpp
+++ b/llvm/lib/IR/BasicBlock.cpp
@@ -975,8 +975,16 @@ void BasicBlock::spliceDebugInfoImpl(BasicBlock::iterator Dest, BasicBlock *Src,
   if (ReadFromTail && Src->getMarker(Last)) {
     DbgMarker *FromLast = Src->getMarker(Last);
     if (LastIsEnd) {
-      Dest->adoptDbgRecords(Src, Last, true);
-      // adoptDbgRecords will release any trailers.
+      if (Dest == end()) {
+        // Abosrb the trailing markers from Src.
+        assert(FromLast == Src->getTrailingDbgRecords());
+        createMarker(Dest)->absorbDebugValues(*FromLast, true);
+        FromLast->eraseFromParent();
+        Src->deleteTrailingDbgRecords();
+      } else {
+        // adoptDbgRecords will release any trailers.
+        Dest->adoptDbgRecords(Src, Last, true);
+      }
       assert(!Src->getTrailingDbgRecords());
     } else {
       // FIXME: can we use adoptDbgRecords here to reduce allocations?
diff --git a/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp b/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp
index 835780e63aaf4f..5615a4493d20a1 100644
--- a/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp
+++ b/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp
@@ -1525,4 +1525,58 @@ TEST(BasicBlockDbgInfoTest, DbgMoveToEnd) {
   EXPECT_FALSE(Ret->hasDbgRecords());
 }
 
+TEST(BasicBlockDbgInfoTest, CloneTrailingRecordsToEmptyBlock) {
+  LLVMContext C;
+  std::unique_ptr<Module> M = parseIR(C, R"(
+    define i16 @foo(i16 %a) !dbg !6 {
+    entry:
+      %b = add i16 %a, 0
+        #dbg_value(i16 %b, !9, !DIExpression(), !11)
+      ret i16 0, !dbg !11
+    }
+
+    !llvm.dbg.cu = !{!0}
+    !llvm.module.flags = !{!5}
+
+    !0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+    !1 = !DIFile(filename: "t.ll", directory: "/")
+    !2 = !{}
+    !5 = !{i32 2, !"Debug Info Version", i32 3}
+    !6 = distinct !DISubprogram(name: "foo", linkageName: "foo", scope: null, file: !1, line: 1, type: !7, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+    !7 = !DISubroutineType(types: !2)
+    !8 = !{!9}
+    !9 = !DILocalVariable(name: "1", scope: !6, file: !1, line: 1, type: !10)
+    !10 = !DIBasicType(name: "ty16", size: 16, encoding: DW_ATE_unsigned)
+    !11 = !DILocation(line: 1, column: 1, scope: !6)
+)");
+  ASSERT_TRUE(M);
+
+  Function *F = M->getFunction("foo");
+  BasicBlock &BB = F->getEntryBlock();
+  // Start with no trailing records.
+  ASSERT_FALSE(BB.getTrailingDbgRecords());
+
+  BasicBlock::iterator Ret = std::prev(BB.end());
+  BasicBlock::iterator B = std::prev(Ret);
+
+  // Delete terminator which has debug records: we now get trailing records.
+  Ret->eraseFromParent();
+  EXPECT_TRUE(BB.getTrailingDbgRecords());
+
+  BasicBlock *NewBB = BasicBlock::Create(C, "NewBB", F);
+  NewBB->splice(NewBB->end(), &BB, B, BB.end());
+
+  // The trailing records should've been absorbed into NewBB.
+  EXPECT_FALSE(BB.getTrailingDbgRecords());
+  EXPECT_TRUE(NewBB->getTrailingDbgRecords());
+  if (NewBB->getTrailingDbgRecords()) {
+    EXPECT_EQ(
+        llvm::range_size(NewBB->getTrailingDbgRecords()->getDbgRecordRange()),
+        1u);
+  }
+
+  // Drop the trailing records now, to prevent a cleanup assertion.
+  NewBB->deleteTrailingDbgRecords();
+}
+
 } // End anonymous namespace.

>From a0dadeb3a4bd7332046b9af811646b730eaec9d1 Mon Sep 17 00:00:00 2001
From: Orlando Cazalet-Hyams <orlando.hyams at sony.com>
Date: Fri, 30 Aug 2024 13:44:42 +0100
Subject: [PATCH 2/2] [RemoveDIs] Fix asan-identified leak in unittest

https://github.com/llvm/llvm-project/pull/106691#issuecomment-2320960847
(cherry picked from commit a80307d0a271223136e0845571606400fb41b2ee)
---
 llvm/unittests/IR/BasicBlockDbgInfoTest.cpp | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp b/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp
index 5615a4493d20a1..5ce14d3f6b9cef 100644
--- a/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp
+++ b/llvm/unittests/IR/BasicBlockDbgInfoTest.cpp
@@ -1569,14 +1569,12 @@ TEST(BasicBlockDbgInfoTest, CloneTrailingRecordsToEmptyBlock) {
   // The trailing records should've been absorbed into NewBB.
   EXPECT_FALSE(BB.getTrailingDbgRecords());
   EXPECT_TRUE(NewBB->getTrailingDbgRecords());
-  if (NewBB->getTrailingDbgRecords()) {
-    EXPECT_EQ(
-        llvm::range_size(NewBB->getTrailingDbgRecords()->getDbgRecordRange()),
-        1u);
+  if (DbgMarker *Trailing = NewBB->getTrailingDbgRecords()) {
+    EXPECT_EQ(llvm::range_size(Trailing->getDbgRecordRange()), 1u);
+    // Drop the trailing records now, to prevent a cleanup assertion.
+    Trailing->eraseFromParent();
+    NewBB->deleteTrailingDbgRecords();
   }
-
-  // Drop the trailing records now, to prevent a cleanup assertion.
-  NewBB->deleteTrailingDbgRecords();
 }
 
 } // End anonymous namespace.