Add -fapply-global-visibility-to-externs for -cc1

[scott.linder]

Summary

Introduce an option to request global visibility settings be applied to declarations without a definition or an explicit visibility, rather than the existing behavior of giving these default visibility. When the visibility of all or most extern definitions are known this allows for the same optimisations -fvisibility permits without updating source code to annotate all declarations.

[scott.linder]

Remove driver options

[rjmccall]

include/clang/Driver/CC1Options.td

707

"Declaration" doesn't unambiguously mean "non-definition" in language parlance;
maybe something like "external declaration" in both help text and the option name?
So maybe -fextern-visibility?

[scott.linder]

Update the -cc1 option name and docs; also update the LangOpt and docs.

[rjmccall]

I'm sorry to keep jerking you around, but let's spell out the flag a bit more: -fapply-global-visibility-to-externs. No reason not to be totally clear here. Thank you for updating the fields and descriptions, those all look good now.

[scott.linder]

No worries, I agree that we don't gain much with a shorter flag here; explicit seems preferable.

[rjmccall]

Thanks, I appreciate you bearing with me on this. LGTM.

include/clang/Basic/LangOptions.def

LANGOPT(
     "Require member pointer base types to be complete at the point where the "
     "type's inheritance model would be determined under the Microsoft ABI")
 
 ENUM_LANGOPT(GC, GCMode, 2, NonGC, "Objective-C Garbage Collection mode")
 ENUM_LANGOPT(ValueVisibilityMode, Visibility, 3, DefaultVisibility,
              "value symbol visibility")
 ENUM_LANGOPT(TypeVisibilityMode, Visibility, 3, DefaultVisibility,
              "type symbol visibility")
+LANGOPT(SetVisibilityForExternDecls, 1, 0,
+        "apply global symbol visibility to external declarations without an explicit visibility")
 ENUM_LANGOPT(StackProtector, StackProtectorMode, 2, SSPOff,
              "stack protector mode")
 ENUM_LANGOPT(TrivialAutoVarInit, TrivialAutoVarInitKind, 2, TrivialAutoVarInitKind::Uninitialized,
              "trivial automatic variable initialization")
 ENUM_LANGOPT(SignedOverflowBehavior, SignedOverflowBehaviorTy, 2, SOB_Undefined,
              "signed integer overflow handling")
 
 BENIGN_LANGOPT(ArrowDepth, 32, 256,

include/clang/Driver/CC1Options.td

 def stack_protector : Separate<["-"], "stack-protector">,
   HelpText<"Enable stack protectors">;
 def stack_protector_buffer_size : Separate<["-"], "stack-protector-buffer-size">,
   HelpText<"Lower bound for a buffer to be considered for stack protection">;
 def fvisibility : Separate<["-"], "fvisibility">,
   HelpText<"Default type and symbol visibility">;
 def ftype_visibility : Separate<["-"], "ftype-visibility">,
   HelpText<"Default type visibility">;
+def fapply_global_visibility_to_externs : Flag<["-"], "fapply-global-visibility-to-externs">,
+  HelpText<"Apply global symbol visibility to external declarations without an explicit visibility">;
 def ftemplate_depth : Separate<["-"], "ftemplate-depth">,
   HelpText<"Maximum depth of recursive template instantiation">;
 def foperator_arrow_depth : Separate<["-"], "foperator-arrow-depth">,
   HelpText<"Maximum number of 'operator->'s to call for a member access">;
 def fconstexpr_depth : Separate<["-"], "fconstexpr-depth">,
   HelpText<"Maximum depth of recursive constexpr function calls">;
 def fconstexpr_steps : Separate<["-"], "fconstexpr-steps">,
   HelpText<"Maximum number of steps in constexpr function evaluation">;

lib/CodeGen/CodeGenModule.cpp

if (GV->hasDLLImportStorageClass())
     return;
   // Internal definitions always have default visibility.
   if (GV->hasLocalLinkage()) {
     GV->setVisibility(llvm::GlobalValue::DefaultVisibility);
     return;
   }
   if (!D)
     return;
-  // Set visibility for definitions.
+  // Set visibility for definitions, and for declarations if requested globally
+  // or set explicitly.
   LinkageInfo LV = D->getLinkageAndVisibility();
-  if (LV.isVisibilityExplicit() || !GV->isDeclarationForLinker())
+  if (LV.isVisibilityExplicit() || getLangOpts().SetVisibilityForExternDecls ||
+      !GV->isDeclarationForLinker())
     GV->setVisibility(GetLLVMVisibility(LV.getVisibility()));
 }
 
 static bool shouldAssumeDSOLocal(const CodeGenModule &CGM,
                                  llvm::GlobalValue *GV) {
   if (GV->hasLocalLinkage())
     return true;
 

lib/Driver/ToolChains/AMDGPU.cpp

void AMDGPUToolChain::addClangTargetOptions(
     llvm::opt::ArgStringList &CC1Args,
     Action::OffloadKind DeviceOffloadingKind) const {
   // Default to "hidden" visibility, as object level linking will not be
   // supported for the foreseeable future.
   if (!DriverArgs.hasArg(options::OPT_fvisibility_EQ,
                          options::OPT_fvisibility_ms_compat)) {
     CC1Args.push_back("-fvisibility");
     CC1Args.push_back("hidden");
+    CC1Args.push_back("-fapply-global-visibility-to-externs");
   }
 }

lib/Driver/ToolChains/HIP.cpp

void HIPToolChain::addClangTargetOptions(
 
   if (DriverArgs.hasFlag(options::OPT_fgpu_rdc, options::OPT_fno_gpu_rdc,
                          false))
     CC1Args.push_back("-fgpu-rdc");
 
   // Default to "hidden" visibility, as object level linking will not be
   // supported for the foreseeable future.
   if (!DriverArgs.hasArg(options::OPT_fvisibility_EQ,
-                         options::OPT_fvisibility_ms_compat))
+                         options::OPT_fvisibility_ms_compat)) {
     CC1Args.append({"-fvisibility", "hidden"});
+    CC1Args.push_back("-fapply-global-visibility-to-externs");
+  }
 }
 
 llvm::opt::DerivedArgList *
 HIPToolChain::TranslateArgs(const llvm::opt::DerivedArgList &Args,
                              StringRef BoundArch,
                              Action::OffloadKind DeviceOffloadKind) const {
   DerivedArgList *DAL =
       HostTC.TranslateArgs(Args, BoundArch, DeviceOffloadKind);

lib/Frontend/CompilerInvocation.cpp

#include "clang/Frontend/LangStandards.def"
   }
 
   if (Args.hasArg(OPT_fvisibility_inlines_hidden))
     Opts.InlineVisibilityHidden = 1;
 
   if (Args.hasArg(OPT_fvisibility_global_new_delete_hidden))
     Opts.GlobalAllocationFunctionVisibilityHidden = 1;
 
+  if (Args.hasArg(OPT_fapply_global_visibility_to_externs))
+    Opts.SetVisibilityForExternDecls = 1;
+
   if (Args.hasArg(OPT_ftrapv)) {
     Opts.setSignedOverflowBehavior(LangOptions::SOB_Trapping);
     // Set the handler, if one is specified.
     Opts.OverflowHandler =
         Args.getLastArgValue(OPT_ftrapv_handler);
   }
   else if (Args.hasArg(OPT_fwrapv))
     Opts.setSignedOverflowBehavior(LangOptions::SOB_Defined);

test/CodeGen/set-visibility-for-decls.c

+// RUN: %clang_cc1 %s -std=c11 -triple=x86_64-pc-linux -fvisibility hidden -fapply-global-visibility-to-externs -emit-llvm -o - | FileCheck --check-prefix=CHECK-HIDDEN %s
+// RUN: %clang_cc1 %s -std=c11 -triple=x86_64-pc-linux -fvisibility protected -fapply-global-visibility-to-externs -emit-llvm -o - | FileCheck --check-prefix=CHECK-PROTECTED %s
+// RUN: %clang_cc1 %s -std=c11 -triple=x86_64-pc-linux -fvisibility default -fapply-global-visibility-to-externs -emit-llvm -o - | FileCheck --check-prefix=CHECK-DEFAULT %s
+
+// CHECK-HIDDEN: @var_hidden = external hidden global
+// CHECK-PROTECTED: @var_hidden = external hidden global
+// CHECK-DEFAULT: @var_hidden = external hidden global
+__attribute__((visibility("hidden"))) extern int var_hidden;
+// CHECK-HIDDEN: @var_protected = external protected global
+// CHECK-PROTECTED: @var_protected = external protected global
+// CHECK-DEFAULT: @var_protected = external protected global
+__attribute__((visibility("protected"))) extern int var_protected;
+// CHECK-HIDDEN: @var_default = external global
+// CHECK-PROTECTED: @var_default = external global
+// CHECK-DEFAULT: @var_default = external global
+__attribute__((visibility("default"))) extern int var_default;
+// CHECK-HIDDEN: @var = external hidden global
+// CHECK-PROTECTED: @var = external protected global
+// CHECK-DEFAULT: @var = external global
+extern int var;
+
+// CHECK-HIDDEN: declare hidden i32 @func_hidden()
+// CHECK-PROTECTED: declare hidden i32 @func_hidden()
+// CHECK-DEFAULT: declare hidden i32 @func_hidden()
+__attribute__((visibility("hidden"))) int func_hidden(void);
+// CHECK-HIDDEN: declare protected i32 @func_protected()
+// CHECK-PROTECTED: declare protected i32 @func_protected()
+// CHECK-DEFAULT: declare protected i32 @func_protected()
+__attribute__((visibility("protected"))) int func_protected(void);
+// CHECK-HIDDEN: declare i32 @func_default()
+// CHECK-PROTECTED: declare i32 @func_default()
+// CHECK-DEFAULT: declare i32 @func_default()
+__attribute__((visibility("default"))) int func_default(void);
+// CHECK-HIDDEN: declare hidden i32 @func()
+// CHECK-PROTECTED: declare protected i32 @func()
+// CHECK-DEFAULT: declare i32 @func()
+int func(void);
+
+int use() {
+  return var_hidden + var_protected + var_default + var +
+         func_hidden() + func_protected() + func_default() + func();
+}

test/Driver/amdgpu-visibility.cl

 // RUN: %clang -### -target amdgcn-amd-amdhsa -x cl -c -emit-llvm %s 2>&1 | FileCheck -check-prefix=DEFAULT %s
 // RUN: %clang -### -target amdgcn-amd-amdhsa -x cl -c -emit-llvm -fvisibility=protected  %s 2>&1 | FileCheck -check-prefix=OVERRIDE-PROTECTED  %s
 // RUN: %clang -### -target amdgcn-amd-amdhsa -x cl -c -emit-llvm -fvisibility-ms-compat  %s 2>&1 | FileCheck -check-prefix=OVERRIDE-MS  %s
 
-// DEFAULT: "-fvisibility" "hidden"
+// DEFAULT-DAG: "-fvisibility" "hidden"
+// DEFAULT-DAG: "-fapply-global-visibility-to-externs"
+
+// OVERRIDE-PROTECTED-NOT: "-fapply-global-visibility-to-externs"
 // OVERRIDE-PROTECTED: "-fvisibility" "protected"
-// OVERRIDE-MS:  "-fvisibility" "hidden" "-ftype-visibility" "default"
+// OVERRIDE-PROTECTED-NOT: "-fapply-global-visibility-to-externs"
+
+// OVERRIDE-MS-NOT: "-fapply-global-visibility-to-externs"
+// OVERRIDE-MS-DAG: "-fvisibility" "hidden"
+// OVERRIDE-MS-DAG: "-ftype-visibility" "default"
+// OVERRIDE-MS-NOT: "-fapply-global-visibility-to-externs"

test/Driver/hip-toolchain-no-rdc.hip

 //
 // Compile device code in a.cu to code object for gfx803.
 //
 
 // CHECK: [[CLANG:".*clang.*"]] "-cc1" "-triple" "amdgcn-amd-amdhsa"
 // CHECK-SAME: "-aux-triple" "x86_64-unknown-linux-gnu" "-emit-llvm-bc"
 // CHECK-SAME: {{.*}} "-main-file-name" "a.cu" {{.*}} "-target-cpu" "gfx803"
 // CHECK-SAME: "-fcuda-is-device" "-fvisibility" "hidden"
+// CHECK-SAME: "-fapply-global-visibility-to-externs"
 // CHECK-SAME: {{.*}} "-o" [[A_BC_803:".*bc"]] "-x" "hip"
 // CHECK-SAME: {{.*}} [[A_SRC:".*a.cu"]]
 
 // CHECK: [[LLVM_LINK:"*.llvm-link"]] [[A_BC_803]]
 // CHECK-SAME: "{{.*}}lib1.bc" "{{.*}}lib2.bc"
 // CHECK-SAME: "-o" [[LINKED_BC_DEV_A_803:".*-gfx803-linked-.*bc"]]
 
 // CHECK: [[OPT:".*opt"]] [[LINKED_BC_DEV_A_803]] "-mtriple=amdgcn-amd-amdhsa"

 //
 // Compile device code in a.cu to code object for gfx900.
 //
 
 // CHECK: [[CLANG:".*clang.*"]] "-cc1" "-triple" "amdgcn-amd-amdhsa"
 // CHECK-SAME: "-aux-triple" "x86_64-unknown-linux-gnu" "-emit-llvm-bc"
 // CHECK-SAME: {{.*}} "-main-file-name" "a.cu" {{.*}} "-target-cpu" "gfx900"
 // CHECK-SAME: "-fcuda-is-device" "-fvisibility" "hidden"
+// CHECK-SAME: "-fapply-global-visibility-to-externs"
 // CHECK-SAME: {{.*}} "-o" [[A_BC_900:".*bc"]] "-x" "hip"
 // CHECK-SAME: {{.*}} [[A_SRC]]
 
 // CHECK: [[LLVM_LINK:"*.llvm-link"]] [[A_BC_900]]
 // CHECK-SAME: "{{.*}}lib1.bc" "{{.*}}lib2.bc"
 // CHECK-SAME: "-o" [[LINKED_BC_DEV_A_900:".*-gfx900-linked-.*bc"]]
 
 // CHECK: [[OPT:".*opt"]] [[LINKED_BC_DEV_A_900]] "-mtriple=amdgcn-amd-amdhsa"

 //
 // Compile device code in b.hip to code object for gfx803.
 //
 
 // CHECK: [[CLANG:".*clang.*"]] "-cc1" "-triple" "amdgcn-amd-amdhsa"
 // CHECK-SAME: "-aux-triple" "x86_64-unknown-linux-gnu" "-emit-llvm-bc"
 // CHECK-SAME: {{.*}} "-main-file-name" "b.hip" {{.*}} "-target-cpu" "gfx803"
 // CHECK-SAME: "-fcuda-is-device" "-fvisibility" "hidden"
+// CHECK-SAME: "-fapply-global-visibility-to-externs"
 // CHECK-SAME: {{.*}} "-o" [[B_BC_803:".*bc"]] "-x" "hip"
 // CHECK-SAME: {{.*}} [[B_SRC:".*b.hip"]]
 
 // CHECK: [[LLVM_LINK:"*.llvm-link"]] [[B_BC_803]]
 // CHECK-SAME: "{{.*}}lib1.bc" "{{.*}}lib2.bc"
 // CHECK-SAME: "-o" [[LINKED_BC_DEV_B_803:".*-gfx803-linked-.*bc"]]
 
 // CHECK: [[OPT:".*opt"]] [[LINKED_BC_DEV_B_803]] "-mtriple=amdgcn-amd-amdhsa"

 //
 // Compile device code in b.hip to code object for gfx900.
 //
 
 // CHECK: [[CLANG:".*clang.*"]] "-cc1" "-triple" "amdgcn-amd-amdhsa"
 // CHECK-SAME: "-aux-triple" "x86_64-unknown-linux-gnu" "-emit-llvm-bc"
 // CHECK-SAME: {{.*}} "-main-file-name" "b.hip" {{.*}} "-target-cpu" "gfx900"
 // CHECK-SAME: "-fcuda-is-device" "-fvisibility" "hidden"
+// CHECK-SAME: "-fapply-global-visibility-to-externs"
 // CHECK-SAME: {{.*}} "-o" [[B_BC_900:".*bc"]] "-x" "hip"
 // CHECK-SAME: {{.*}} [[B_SRC]]
 
 // CHECK: [[LLVM_LINK:"*.llvm-link"]] [[B_BC_900]]
 // CHECK-SAME: "{{.*}}lib1.bc" "{{.*}}lib2.bc"
 // CHECK-SAME: "-o" [[LINKED_BC_DEV_B_900:".*-gfx900-linked-.*bc"]]
 
 // CHECK: [[OPT:".*opt"]] [[LINKED_BC_DEV_B_900]] "-mtriple=amdgcn-amd-amdhsa"

test/Driver/hip-toolchain-rdc.hip

 // REQUIRES: clang-driver
 // REQUIRES: x86-registered-target
 // REQUIRES: amdgpu-registered-target
 
 // RUN: %clang -### -target x86_64-linux-gnu \
 // RUN:   -x hip --cuda-gpu-arch=gfx803 --cuda-gpu-arch=gfx900 \
 // RUN:   --hip-device-lib=lib1.bc --hip-device-lib=lib2.bc \
 // RUN:   --hip-device-lib-path=%S/Inputs/hip_multiple_inputs/lib1 \
 // RUN:   --hip-device-lib-path=%S/Inputs/hip_multiple_inputs/lib2 \
 // RUN:   -fuse-ld=lld -fgpu-rdc \
 // RUN:   %S/Inputs/hip_multiple_inputs/a.cu \
 // RUN:   %S/Inputs/hip_multiple_inputs/b.hip \
 // RUN: 2>&1 | FileCheck %s
 
-// CHECK: [[CLANG:".*clang.*"]] "-cc1" "-triple" "amdgcn-amd-amdhsa" 
+// CHECK: [[CLANG:".*clang.*"]] "-cc1" "-triple" "amdgcn-amd-amdhsa"
 // CHECK-SAME: "-aux-triple" "x86_64-unknown-linux-gnu" "-emit-llvm-bc"
 // CHECK-SAME: {{.*}} "-main-file-name" "a.cu" {{.*}} "-target-cpu" "gfx803"
 // CHECK-SAME: "-fcuda-is-device" "-fgpu-rdc" "-fvisibility" "hidden"
+// CHECK-SAME: "-fapply-global-visibility-to-externs"
 // CHECK-SAME: {{.*}} "-o" [[A_BC:".*bc"]] "-x" "hip"
 // CHECK-SAME: {{.*}} [[A_SRC:".*a.cu"]]
 
 // CHECK: [[CLANG]] "-cc1" "-triple" "amdgcn-amd-amdhsa"
 // CHECK-SAME: "-aux-triple" "x86_64-unknown-linux-gnu" "-emit-llvm-bc"
 // CHECK-SAME: {{.*}} "-main-file-name" "b.hip" {{.*}} "-target-cpu" "gfx803"
 // CHECK-SAME: "-fcuda-is-device" "-fgpu-rdc" "-fvisibility" "hidden"
+// CHECK-SAME: "-fapply-global-visibility-to-externs"
 // CHECK-SAME: {{.*}} "-o" [[B_BC:".*bc"]] "-x" "hip"
 // CHECK-SAME: {{.*}} [[B_SRC:".*b.hip"]]
 
 // CHECK: [[LLVM_LINK:"*.llvm-link"]] [[A_BC]] [[B_BC]]
 // CHECK-SAME: "{{.*}}lib1.bc" "{{.*}}lib2.bc"
 // CHECK-SAME: "-o" [[LINKED_BC_DEV1:".*-gfx803-linked-.*bc"]]
 
 // CHECK: [[OPT:".*opt"]] [[LINKED_BC_DEV1]] "-mtriple=amdgcn-amd-amdhsa"