From 9a878c4930b586bac36495aedfbceabab6906cd1 Mon Sep 17 00:00:00 2001
From: Nirav Dave <niravd@google.com>
Date: Fri, 22 Apr 2016 13:36:11 +0000
Subject: Emit code16 in assembly in 16-bit mode

Summary:
When generating assembly using -m16 we must explicitly mark it as
16-bit. Emit .code16 at beginning of file. Fixes wrong results when
using -fno-integrated-as.

Reviewers: dwmw2

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D19392

llvm-svn: 267152
---
 llvm/lib/Target/X86/X86AsmPrinter.cpp |  6 ++++++
 llvm/test/CodeGen/X86/x86-16.ll       | 20 ++++++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 llvm/test/CodeGen/X86/x86-16.ll

diff --git a/llvm/lib/Target/X86/X86AsmPrinter.cpp b/llvm/lib/Target/X86/X86AsmPrinter.cpp
index 9d0ac319859..0a00463f8bf 100644
--- a/llvm/lib/Target/X86/X86AsmPrinter.cpp
+++ b/llvm/lib/Target/X86/X86AsmPrinter.cpp
@@ -538,6 +538,12 @@ void X86AsmPrinter::EmitStartOfAsmFile(Module &M) {
     }
   }
   OutStreamer->EmitSyntaxDirective();
+
+  // If this is not inline asm and we're in 16-bit
+  // mode prefix assembly with .code16.
+  bool is16 = TT.getEnvironment() == Triple::CODE16;
+  if (M.getModuleInlineAsm().empty() && is16)
+    OutStreamer->EmitAssemblerFlag(MCAF_Code16);
 }
 
 static void
diff --git a/llvm/test/CodeGen/X86/x86-16.ll b/llvm/test/CodeGen/X86/x86-16.ll
new file mode 100644
index 00000000000..775b2c447bb
--- /dev/null
+++ b/llvm/test/CodeGen/X86/x86-16.ll
@@ -0,0 +1,20 @@
+; RUN: llc < %s | FileCheck %s
+target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i386-unknown-linux-code16"
+
+; Function Attrs: nounwind
+define i32 @main() #0 {
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  ret i32 0
+}
+
+; CHECK: .code16
+; CHECK-LABEL: main
+
+
+attributes #0 = { nounwind }
+
+!llvm.ident = !{!0}
+
+!0 = !{!"clang version 3.9.0 (trunk 265439) (llvm/trunk 265567)"}
\ No newline at end of file
-- 
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