allow COFF .def directive in module assembly when using ThinLTO

Summary:
Using COFF's .def directive in module assembly used to crash ThinLTO
with "this directive only supported on COFF targets" when getting
symbol information in ModuleSymbolTable.  This change allows
ModuleSymbolTable to process such code and adds a test to verify that
the .def directive has the desired effect on the native object file,
with and without ThinLTO.

Fixes https://bugs.llvm.org/show_bug.cgi?id=36789

Reviewers: rnk, pcc, vlad.tsyrklevich

Subscribers: mehdi_amini, eraman, hiraditya, dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D57073

llvm-svn: 352112

2 files changed, 30 insertions, 0 deletions

diff --git a/llvm/lib/Object/RecordStreamer.h b/llvm/lib/Object/RecordStreamer.h
index ac501725ecd..5ac9cd6a4f5 100644
--- a/llvm/lib/Object/RecordStreamer.h
+++ b/llvm/lib/Object/RecordStreamer.h
@@ -55,6 +55,15 @@ public:
                     unsigned ByteAlignment, SMLoc Loc = SMLoc()) override;
   void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                         unsigned ByteAlignment) override;
+
+  // Ignore COFF-specific directives; we do not need any information from them,
+  // but the default implementation of these methods crashes, so we override
+  // them with versions that do nothing.
+  void BeginCOFFSymbolDef(const MCSymbol *Symbol) override {}
+  void EmitCOFFSymbolStorageClass(int StorageClass) override {}
+  void EmitCOFFSymbolType(int Type) override {}
+  void EndCOFFSymbolDef() override {}
+
   /// Record .symver aliases for later processing.
   void emitELFSymverDirective(StringRef AliasName,
                               const MCSymbol *Aliasee) override;
diff --git a/llvm/test/MC/COFF/module-asm-coff.ll b/llvm/test/MC/COFF/module-asm-coff.ll
new file mode 100644
index 00000000000..38e108031d3
--- /dev/null
+++ b/llvm/test/MC/COFF/module-asm-coff.ll
@@ -0,0 +1,21 @@
+; Tests COFF-specific directives in module level assembly.
+
+; RUN: llc -filetype=obj %s -o %t.obj
+; RUN: llvm-readobj -t %t.obj | FileCheck %s
+; RUN: opt -thinlto-bc %s -o %t.thinlto.bc
+; RUN: llvm-lto2 run %t.thinlto.bc -o %t.thinlto.obj -r=%t.thinlto.bc,foo,plx
+; RUN: llvm-readobj -t %t.thinlto.obj.1 | FileCheck %s
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.0.24210"
+
+module asm ".text"
+module asm ".def foo; .scl 3; .type 32; .endef"
+module asm ".global foo"
+module asm "foo:"
+module asm "  ret"
+
+; CHECK: Symbol {
+; CHECK:   Name: foo
+; CHECK:   StorageClass:
+; CHECK-SAME: Static (0x3)