[Driver] Properly support -mglobal-merge using explicit options.

Follow-up to r234666.  With this, the -m[no-]global-merge options
have the expected behavior. Previously, -mglobal-merge was ignored,
and there was no way of enabling the optimization.

llvm-svn: 234668

clang/include/clang/Driver/Options.td

@@ -1146,7 +1146,8 @@ def mfloat_abi_EQ : Joined<["-"], "mfloat-abi=">, Group<m_Group>;
 def mfpmath_EQ : Joined<["-"], "mfpmath=">, Group<m_Group>;
 def mfpu_EQ : Joined<["-"], "mfpu=">, Group<m_Group>;
 def mhwdiv_EQ : Joined<["-"], "mhwdiv=">, Group<m_Group>;
-def mglobal_merge : Flag<["-"], "mglobal-merge">, Group<m_Group>;
+def mglobal_merge : Flag<["-"], "mglobal-merge">, Group<m_Group>, Flags<[CC1Option]>,
+  HelpText<"Enable merging of globals">;
 def mhard_float : Flag<["-"], "mhard-float">, Group<m_Group>;
 def miphoneos_version_min_EQ : Joined<["-"], "miphoneos-version-min=">, Group<m_Group>;
 def mios_version_min_EQ : Joined<["-"], "mios-version-min=">,

clang/include/clang/Frontend/CodeGenOptions.def

@@ -77,7 +77,6 @@ CODEGENOPT(NoExecStack       , 1, 0) ///< Set when -Wa,--noexecstack is enabled.
 CODEGENOPT(FatalWarnings     , 1, 0) ///< Set when -Wa,--fatal-warnings is
                                      ///< enabled.
 CODEGENOPT(EnableSegmentedStacks , 1, 0) ///< Set when -fsplit-stack is enabled.
-CODEGENOPT(NoGlobalMerge     , 1, 0) ///< Set when -mno-global-merge is enabled.
 CODEGENOPT(NoImplicitFloat   , 1, 0) ///< Set when -mno-implicit-float is enabled.
 CODEGENOPT(NoInfsFPMath      , 1, 0) ///< Assume FP arguments, results not +-Inf.
 CODEGENOPT(NoSignedZeros     , 1, 0) ///< Allow ignoring the signedness of FP zero

clang/lib/CodeGen/BackendUtil.cpp

@@ -436,8 +436,6 @@ TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
     BackendArgs.push_back("-time-passes");
   for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
     BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
-  if (CodeGenOpts.NoGlobalMerge)
-    BackendArgs.push_back("-enable-global-merge=false");
   BackendArgs.push_back(nullptr);
   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
                                     BackendArgs.data());

clang/lib/Driver/Tools.cpp

@@ -861,12 +861,14 @@ void Clang::AddARMTargetArgs(const ArgList &Args,
     }
   }
 
-  // Setting -mno-global-merge disables the codegen global merge pass. Setting 
-  // -mglobal-merge has no effect as the pass is enabled by default.
+  // Forward the -mglobal-merge option for explicit control over the pass.
   if (Arg *A = Args.getLastArg(options::OPT_mglobal_merge,
                                options::OPT_mno_global_merge)) {
+    CmdArgs.push_back("-backend-option");
     if (A->getOption().matches(options::OPT_mno_global_merge))
-      CmdArgs.push_back("-mno-global-merge");
+      CmdArgs.push_back("-arm-global-merge=false");
+    else
+      CmdArgs.push_back("-arm-global-merge=true");
   }
 
   if (!Args.hasFlag(options::OPT_mimplicit_float,
@@ -957,12 +959,14 @@ void Clang::AddAArch64TargetArgs(const ArgList &Args,
     CmdArgs.push_back("-aarch64-fix-cortex-a53-835769=1");
   }
 
-  // Setting -mno-global-merge disables the codegen global merge pass. Setting
-  // -mglobal-merge has no effect as the pass is enabled by default.
+  // Forward the -mglobal-merge option for explicit control over the pass.
   if (Arg *A = Args.getLastArg(options::OPT_mglobal_merge,
                                options::OPT_mno_global_merge)) {
+    CmdArgs.push_back("-backend-option");
     if (A->getOption().matches(options::OPT_mno_global_merge))
-      CmdArgs.push_back("-mno-global-merge");
+      CmdArgs.push_back("-aarch64-global-merge=false");
+    else
+      CmdArgs.push_back("-aarch64-global-merge=true");
   }
 
   if (Args.hasArg(options::OPT_ffixed_x18)) {

clang/lib/Frontend/CompilerInvocation.cpp

@@ -455,7 +455,6 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.NoZeroInitializedInBSS = Args.hasArg(OPT_mno_zero_initialized_in_bss);
   Opts.BackendOptions = Args.getAllArgValues(OPT_backend_option);
   Opts.NumRegisterParameters = getLastArgIntValue(Args, OPT_mregparm, 0, Diags);
-  Opts.NoGlobalMerge = Args.hasArg(OPT_mno_global_merge);
   Opts.NoExecStack = Args.hasArg(OPT_mno_exec_stack);
   Opts.FatalWarnings = Args.hasArg(OPT_massembler_fatal_warnings);
   Opts.EnableSegmentedStacks = Args.hasArg(OPT_split_stacks);

clang/test/Driver/mglobal-merge.c

@@ -0,0 +1,40 @@
+// RUN: %clang -target armv7-unknown-unknown -### -fsyntax-only %s 2> %t \
+// RUN:   -mno-global-merge
+// RUN: FileCheck --check-prefix=CHECK-NGM-ARM < %t %s
+
+// RUN: %clang -target aarch64-unknown-unknown -### -fsyntax-only %s 2> %t \
+// RUN:   -mno-global-merge
+// RUN: FileCheck --check-prefix=CHECK-NGM-AARCH64 < %t %s
+
+// RUN: %clang -target x86_64-unknown-unknown -### -fsyntax-only %s 2> %t \
+// RUN:   -mno-global-merge
+// RUN: FileCheck --check-prefix=CHECK-NONE < %t %s
+
+// CHECK-NGM-ARM: "-backend-option" "-arm-global-merge=false"
+// CHECK-NGM-AARCH64: "-backend-option" "-aarch64-global-merge=false"
+
+// RUN: %clang -target armv7-unknown-unknown -### -fsyntax-only %s 2> %t \
+// RUN:   -mglobal-merge
+// RUN: FileCheck --check-prefix=CHECK-GM-ARM < %t %s
+
+// RUN: %clang -target aarch64-unknown-unknown -### -fsyntax-only %s 2> %t \
+// RUN:   -mglobal-merge
+// RUN: FileCheck --check-prefix=CHECK-GM-AARCH64 < %t %s
+
+// RUN: %clang -target x86_64-unknown-unknown -### -fsyntax-only %s 2> %t \
+// RUN:   -mglobal-merge
+// RUN: FileCheck --check-prefix=CHECK-NONE < %t %s
+
+// CHECK-GM-ARM: "-backend-option" "-arm-global-merge=true"
+// CHECK-GM-AARCH64: "-backend-option" "-aarch64-global-merge=true"
+
+// RUN: %clang -target armv7-unknown-unknown -### -fsyntax-only %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-NONE < %t %s
+
+// RUN: %clang -target aarch64-unknown-unknown -### -fsyntax-only %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-NONE < %t %s
+
+// RUN: %clang -target x86_64-unknown-unknown -### -fsyntax-only %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-NONE < %t %s
+
+// CHECK-NONE-NOT: -global-merge=

clang/test/Driver/mno-global-merge.c

@@ -1,20 +0,0 @@
-// RUN: %clang -target armv7-apple-darwin10 \
-// RUN:   -mno-global-merge -### -fsyntax-only %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-NGM < %t %s
-
-// RUN: %clang -target arm64-apple-ios7 \
-// RUN:   -mno-global-merge -### -fsyntax-only %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-NGM < %t %s
-
-// CHECK-NGM: "-mno-global-merge"
-
-// RUN: %clang -target armv7-apple-darwin10 \
-// RUN:   -mglobal-merge -### -fsyntax-only %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-GM < %t %s
-
-// RUN: %clang -target arm64-apple-ios7 \
-// RUN:   -mglobal-merge -### -fsyntax-only %s 2> %t
-// RUN: FileCheck --check-prefix=CHECK-GM < %t %s
-
-// CHECK-GM-NOT: "-mglobal-merge"
-