Ignore !associated metadata with null argument.

Fixes PR32577 (comment 10).
Such metadata may legitimately appear in LTO.

llvm-svn: 302485

2 files changed, 10 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 34892680ace..1d232c71d82 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -232,7 +232,11 @@ static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
   if (!MD)
     return nullptr;
 
-  auto *VM = dyn_cast<ValueAsMetadata>(MD->getOperand(0));
+  const MDOperand &Op = MD->getOperand(0);
+  if (!Op.get())
+    return nullptr;
+
+  auto *VM = dyn_cast<ValueAsMetadata>(Op);
   if (!VM)
     report_fatal_error("MD_associated operand is not ValueAsMetadata");
 
diff --git a/llvm/test/CodeGen/X86/elf-associated.ll b/llvm/test/CodeGen/X86/elf-associated.ll
index 361cf66cce7..7d58c343702 100644
--- a/llvm/test/CodeGen/X86/elf-associated.ll
+++ b/llvm/test/CodeGen/X86/elf-associated.ll
@@ -37,3 +37,8 @@
 @l = global i32 1, section "ccc", !associated !5
 !5 = !{i32* null}
 ; CHECK-DAG: .section	ccc,"aw",@progbits
+
+; Null metadata.
+@m = global i32 1, section "ddd", !associated !6
+!6 = distinct !{null}
+; CHECK-DAG: .section	ddd,"aw",@progbits