[MC] Pass through .code16/32/64 and .syntax unified for COFF

These flags should simply be passed through to the target, which will do
the right thing. Add an MC/X86 test that uses these directives with the
three primary object file formats and shows that they disassemble the
same everywhere.

There is a missing test for .code32 on Windows ARM, since I'm not sure
exactly how to construct one.

Fixes PR43203

llvm-svn: 370805

3 files changed, 34 insertions, 11 deletions

diff --git a/llvm/lib/MC/MCWinCOFFStreamer.cpp b/llvm/lib/MC/MCWinCOFFStreamer.cpp
index 04d5f100a2f..40470452686 100644
--- a/llvm/lib/MC/MCWinCOFFStreamer.cpp
+++ b/llvm/lib/MC/MCWinCOFFStreamer.cpp
@@ -88,7 +88,19 @@ void MCWinCOFFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) {
 }
 
 void MCWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
-  llvm_unreachable("not implemented");
+  // Let the target do whatever target specific stuff it needs to do.
+  getAssembler().getBackend().handleAssemblerFlag(Flag);
+
+  switch (Flag) {
+  // None of these require COFF specific handling.
+  case MCAF_SyntaxUnified:
+  case MCAF_Code16:
+  case MCAF_Code32:
+  case MCAF_Code64:
+    break;
+  case MCAF_SubsectionsViaSymbols:
+    llvm_unreachable("COFF doesn't support .subsections_via_symbols");
+  }
 }
 
 void MCWinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFStreamer.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFStreamer.cpp
index 2e816bea5e9..b3c8146a9bd 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFStreamer.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFStreamer.cpp
@@ -22,20 +22,10 @@ public:
                      std::unique_ptr<MCObjectWriter> OW)
       : MCWinCOFFStreamer(C, std::move(AB), std::move(CE), std::move(OW)) {}
 
-  void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
   void EmitThumbFunc(MCSymbol *Symbol) override;
   void FinishImpl() override;
 };
 
-void ARMWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
-  switch (Flag) {
-  default: llvm_unreachable("not implemented");
-  case MCAF_SyntaxUnified:
-  case MCAF_Code16:
-    break;
-  }
-}
-
 void ARMWinCOFFStreamer::EmitThumbFunc(MCSymbol *Symbol) {
   getAssembler().setIsThumbFunc(Symbol);
 }
diff --git a/llvm/test/MC/X86/code16-32-64.s b/llvm/test/MC/X86/code16-32-64.s
new file mode 100644
index 00000000000..42da46a06d0
--- /dev/null
+++ b/llvm/test/MC/X86/code16-32-64.s
@@ -0,0 +1,21 @@
+# RUN: llvm-mc %s -triple x86_64-linux-gnu -filetype=obj -o - | llvm-objdump -d - | FileCheck %s
+# RUN: llvm-mc %s -triple x86_64-windows-msvc -filetype=obj -o - | llvm-objdump -d - | FileCheck %s
+# RUN: llvm-mc %s -triple x86_64-apple-macos -filetype=obj -o - | llvm-objdump -d - | FileCheck %s
+
+.text
+.global foo
+foo:
+	.code64
+	movl (%eax), %eax
+	.code32
+	movl (%eax), %eax
+	.code16
+	movl (%eax), %eax
+	.code64
+	retq
+
+# CHECK: foo:
+# CHECK-NEXT: 67 8b 00                      movl    (%eax), %eax
+# CHECK-NEXT: 8b 00                         movl    (%rax), %eax
+# CHECK-NEXT: 67 66 8b 00                   movw    (%eax), %ax
+# CHECK-NEXT: c3                            retq