[Driver] Add support for -fembed-bitcode for assembly file

Summary:
Handle -fembed-bitcode for assembly inputs. When the input file is
assembly, write a marker as "__LLVM,__asm" section.

Fix llvm.org/pr39659

Reviewers: compnerd, dexonsmith

Reviewed By: compnerd

Subscribers: rjmccall, dblaikie, jkorous, cfe-commits

Differential Revision: https://reviews.llvm.org/D55525

llvm-svn: 348943

1 files changed, 23 insertions, 0 deletions

diff --git a/clang/tools/driver/cc1as_main.cpp b/clang/tools/driver/cc1as_main.cpp
index 9e454cdd0f4..be4f174ed41 100644
--- a/clang/tools/driver/cc1as_main.cpp
+++ b/clang/tools/driver/cc1as_main.cpp
@@ -33,6 +33,7 @@
 #include "llvm/MC/MCParser/MCAsmParser.h"
 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
 #include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCSectionMachO.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/MC/MCTargetOptions.h"
@@ -132,6 +133,7 @@ struct AssemblerInvocation {
   unsigned NoExecStack : 1;
   unsigned FatalWarnings : 1;
   unsigned IncrementalLinkerCompatible : 1;
+  unsigned EmbedBitcode : 1;
 
   /// The name of the relocation model to use.
   std::string RelocationModel;
@@ -153,6 +155,7 @@ public:
     FatalWarnings = 0;
     IncrementalLinkerCompatible = 0;
     DwarfVersion = 0;
+    EmbedBitcode = 0;
   }
 
   static bool CreateFromArgs(AssemblerInvocation &Res,
@@ -284,6 +287,16 @@ bool AssemblerInvocation::CreateFromArgs(AssemblerInvocation &Opts,
       Args.hasArg(OPT_mincremental_linker_compatible);
   Opts.SymbolDefs = Args.getAllArgValues(OPT_defsym);
 
+  // EmbedBitcode Option. If -fembed-bitcode is enabled, set the flag.
+  // EmbedBitcode behaves the same for all embed options for assembly files.
+  if (auto *A = Args.getLastArg(OPT_fembed_bitcode_EQ)) {
+    Opts.EmbedBitcode = llvm::StringSwitch<unsigned>(A->getValue())
+                            .Case("all", 1)
+                            .Case("bitcode", 1)
+                            .Case("marker", 1)
+                            .Default(0);
+  }
+
   return Success;
 }
 
@@ -449,6 +462,16 @@ static bool ExecuteAssembler(AssemblerInvocation &Opts,
     Str.get()->InitSections(Opts.NoExecStack);
   }
 
+  // When -fembed-bitcode is passed to clang_as, a 1-byte marker
+  // is emitted in __LLVM,__asm section if the object file is MachO format.
+  if (Opts.EmbedBitcode && Ctx.getObjectFileInfo()->getObjectFileType() ==
+                               MCObjectFileInfo::IsMachO) {
+    MCSection *AsmLabel = Ctx.getMachOSection(
+        "__LLVM", "__asm", MachO::S_REGULAR, 4, SectionKind::getReadOnly());
+    Str.get()->SwitchSection(AsmLabel);
+    Str.get()->EmitZeros(1);
+  }
+
   // Assembly to object compilation should leverage assembly info.
   Str->setUseAssemblerInfoForParsing(true);