Revert r337333, "Teach Clang to emit address-significance tables."

Causing multiple failures on sanitizer bots due to TLS symbol errors,
e.g.

/usr/bin/ld: __msan_origin_tls: TLS definition in /home/buildbots/ppc64be-clang-test/clang-ppc64be/stage1/lib/clang/7.0.0/lib/linux/libclang_rt.msan-powerpc64.a(msan.cc.o) section .tbss.__msan_origin_tls mismatches non-TLS reference in /tmp/lit_tmp_0a71tA/mallinfo-3ca75e.o

llvm-svn: 337336

clang/docs/ReleaseNotes.rst

@@ -98,14 +98,6 @@ Non-comprehensive list of changes in this release
   finding out the warning hierarchy, and which of them are enabled by default
   or for a particular compiler invocation.
 
-- By default, Clang emits an address-significance table into
-  every ELF object file when using the integrated assembler.
-  Address-significance tables allow linkers to implement `safe ICF
-  <https://research.google.com/pubs/archive/36912.pdf>`_ without the false
-  positives that can result from other implementation techniques such as
-  relocation scanning. The ``-faddrsig`` and ``-fno-addrsig`` flags can be
-  used to control whether to emit the address-significance table.
-
 - ...
 
 New Compiler Flags

clang/docs/UsersManual.rst

@@ -1382,15 +1382,6 @@ are listed below.
         // value of -fmax-type-align.
       }
 
-.. option:: -faddrsig, -fno-addrsig
-
-   Controls whether Clang emits an address-significance table into the object
-   file. Address-significance tables allow linkers to implement `safe ICF
-   <https://research.google.com/pubs/archive/36912.pdf>`_ without the false
-   positives that can result from other implementation techniques such as
-   relocation scanning. Address-significance tables are enabled by default
-   on ELF targets when using the integrated assembler. This flag currently
-   only has an effect on ELF targets.
 
 Profile Guided Optimization
 ---------------------------

clang/include/clang/Driver/Options.td

@@ -758,10 +758,6 @@ def fno_profile_instr_use : Flag<["-"], "fno-profile-instr-use">,
 def fno_profile_use : Flag<["-"], "fno-profile-use">,
     Alias<fno_profile_instr_use>;
 
-def faddrsig : Flag<["-"], "faddrsig">, Group<f_Group>, Flags<[CoreOption, CC1Option]>,
-  HelpText<"Emit an address-significance table">;
-def fno_addrsig : Flag<["-"], "fno-addrsig">, Group<f_Group>, Flags<[CoreOption]>,
-  HelpText<"Don't emit an address-significance table">;
 def fblocks : Flag<["-"], "fblocks">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Enable the 'blocks' language feature">;
 def fbootclasspath_EQ : Joined<["-"], "fbootclasspath=">, Group<f_Group>;

clang/include/clang/Frontend/CodeGenOptions.def

@@ -335,9 +335,6 @@ CODEGENOPT(EmbedSource, 1, 0)
 /// Whether to emit all vtables
 CODEGENOPT(ForceEmitVTables, 1, 0)
 
-/// Whether to emit an address-significance table into the object file.
-CODEGENOPT(Addrsig, 1, 0)
-
 
 #undef CODEGENOPT
 #undef ENUM_CODEGENOPT

clang/lib/CodeGen/BackendUtil.cpp

@@ -454,7 +454,6 @@ static void initTargetOptions(llvm::TargetOptions &Options,
   Options.ExplicitEmulatedTLS = CodeGenOpts.ExplicitEmulatedTLS;
   Options.DebuggerTuning = CodeGenOpts.getDebuggerTuning();
   Options.EmitStackSizeSection = CodeGenOpts.StackSizeSection;
-  Options.EmitAddrsig = CodeGenOpts.Addrsig;
 
   if (CodeGenOpts.EnableSplitDwarf)
     Options.MCOptions.SplitDwarfFile = CodeGenOpts.SplitDwarfFile;

clang/lib/Driver/ToolChains/Clang.cpp

@@ -4777,11 +4777,6 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     }
   }
 
-  if (Args.hasFlag(options::OPT_faddrsig, options::OPT_fno_addrsig,
-                   getToolChain().getTriple().isOSBinFormatELF() &&
-                       getToolChain().useIntegratedAs()))
-    CmdArgs.push_back("-faddrsig");
-
   // Finally add the compile command to the compilation.
   if (Args.hasArg(options::OPT__SLASH_fallback) &&
       Output.getType() == types::TY_Object &&

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1119,8 +1119,6 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
 
   Opts.EmitVersionIdentMetadata = Args.hasFlag(OPT_Qy, OPT_Qn, true);
 
-  Opts.Addrsig = Args.hasArg(OPT_faddrsig);
-
   return Success;
 }
 

clang/test/CodeGen/addrsig.c

@@ -1,18 +0,0 @@
-// RUN: %clang_cc1 -triple=x86_64-unknown-linux -S %s -faddrsig -O -o - | FileCheck --check-prefix=ADDRSIG %s
-// RUN: %clang_cc1 -triple=x86_64-unknown-linux -S %s -O -o - | FileCheck --check-prefix=NO-ADDRSIG %s
-
-// ADDRSIG: .addrsig
-// ADDRSIG: .addrsig_sym g1
-// ADDRSIG-NOT: .addrsig_sym g2
-
-// NO-ADDRSIG-NOT: .addrsig
-
-extern const int g1[], g2[];
-
-const int *f1() {
-  return g1;
-}
-
-int f2() {
-  return g2[0];
-}

clang/test/Driver/addrsig.c

@@ -1,8 +0,0 @@
-// RUN: %clang -### -target x86_64-unknown-linux -c %s 2>&1 | FileCheck -check-prefix=ADDRSIG %s
-// RUN: %clang -### -target x86_64-unknown-linux -fno-integrated-as -c %s 2>&1 | FileCheck -check-prefix=NO-ADDRSIG %s
-// RUN: %clang -### -target x86_64-unknown-linux -fno-integrated-as -faddrsig -c %s 2>&1 | FileCheck -check-prefix=ADDRSIG %s
-// RUN: %clang -### -target x86_64-unknown-linux -fno-addrsig -c %s 2>&1 | FileCheck -check-prefix=NO-ADDRSIG %s
-// RUN: %clang -### -target x86_64-apple-darwin -c %s 2>&1 | FileCheck -check-prefix=NO-ADDRSIG %s
-
-// ADDRSIG: -faddrsig
-// NO-ADDRSIG-NOT: -faddrsig