release/19.x: [RemoveDIs] Fix spliceDebugInfo splice-to-end edge case (#105671) #106691
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Fix llvm#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 43661a1)
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@jmorse What do you think about merging this PR to the release branch? |
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@llvm/pr-subscribers-llvm-ir Author: None (llvmbot) ChangesBackport 43661a1 Requested by: @OCHyams Full diff: https://github.com./llvm/llvm-project/pull/106691.diff 2 Files Affected:
diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
index bf19934da047c4..103ec0da4763fd 100644
--- a/llvm/lib/IR/BasicBlock.cpp
+++ b/llvm/lib/IR/BasicBlock.cpp
@@ -971,8 +971,16 @@ 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 91a0745a0cc76e..e6f8df2762e81e 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.
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Edge-case |
I feel this is safe to go into the release branch; I don't think it should block the 19.0.0 release though, better to have it in a point release. This fault has been present for roughly five months and has only just been uncovered, so IMHO it's not a pressing issue. |
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We are seeing ASAN errors past 43661a1214353ea1773a711f403f8d1118e9ca0f: AddressSanitizer: 120 byte(s) leaked in 2 allocation(s). |
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Thanks for the report, I'll look at that now |
OCHyams
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Aug 30, 2024
dklimkin
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Aug 30, 2024
Fixes issue found here #106691 (comment) The issue wasn't in the code change itself, just the unittest; the trailing marker wasn't properly cleaned up.
OCHyams
added a commit
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Sep 2, 2024
llvm#106691 (comment) (cherry picked from commit a80307d)
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Re-opened backport request with the fix too - #106952 |
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Backport 43661a1
Requested by: @OCHyams