[llvm] d1fd723 - Refactor how -fno-semantic-interposition sets dso_local on default visibility external linkage definitions
Fangrui Song via llvm-commits
llvm-commits at lists.llvm.org
Thu Dec 31 13:59:59 PST 2020
Author: Fangrui Song
Date: 2020-12-31T13:59:45-08:00
New Revision: d1fd72343c6ff58a3b66bc0df56fed9ac21e4056
URL: https://github.com/llvm/llvm-project/commit/d1fd72343c6ff58a3b66bc0df56fed9ac21e4056
DIFF: https://github.com/llvm/llvm-project/commit/d1fd72343c6ff58a3b66bc0df56fed9ac21e4056.diff
LOG: Refactor how -fno-semantic-interposition sets dso_local on default visibility external linkage definitions
The idea is that the CC1 default for ELF should set dso_local on default
visibility external linkage definitions in the default -mrelocation-model pic
mode (-fpic/-fPIC) to match COFF/Mach-O and make output IR similar.
The refactoring is made available by 2820a2ca3a0e69c3f301845420e0067ffff2251b.
Currently only x86 supports local aliases. We move the decision to the driver.
There are three CC1 states:
* -fsemantic-interposition: make some linkages interposable and make default visibility external linkage definitions dso_preemptable.
* (default): selected if the target supports .Lfoo$local: make default visibility external linkage definitions dso_local
* -fhalf-no-semantic-interposition: if neither option is set or the target does not support .Lfoo$local: like -fno-semantic-interposition but local aliases are not used. So references can be interposed if not optimized out.
Add -fhalf-no-semantic-interposition to a few tests using the half-based semantic interposition behavior.
Added:
Modified:
clang/include/clang/Basic/LangOptions.def
clang/include/clang/Driver/Options.td
clang/lib/CodeGen/CodeGenModule.cpp
clang/lib/Driver/ToolChains/Clang.cpp
clang/lib/Frontend/CompilerInvocation.cpp
clang/test/CodeGen/attr-arm-sve-vector-bits-globals.c
clang/test/CodeGen/semantic-interposition.c
clang/test/CodeGenCXX/RelativeVTablesABI/child-inheritted-from-parent-in-comdat.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-1.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-2.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/diamond-inheritance.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/diamond-virtual-inheritance.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/inheritted-virtual-function.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/inline-virtual-function.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/multiple-inheritance.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/no-alias-when-dso-local.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/override-pure-virtual-method.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/overriden-virtual-function.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/relative-vtables-flag.cpp
clang/test/CodeGenCXX/RelativeVTablesABI/simple-vtable-definition.cpp
clang/test/Driver/fsemantic-interposition.c
llvm/include/llvm/IR/Module.h
llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
llvm/lib/IR/Module.cpp
Removed:
clang/test/CodeGen/semantic-interposition-no.c
################################################################################
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index cc5eb939dbd2..963fde5f3ad4 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -322,7 +322,8 @@ ENUM_LANGOPT(ExternDeclDLLImportVisibility, Visibility, 3, DefaultVisibility,
ENUM_LANGOPT(ExternDeclNoDLLStorageClassVisibility, Visibility, 3, HiddenVisibility,
"visibility for external declarations without an explicit DLL storage class [-fvisibility-from-dllstorageclass]")
BENIGN_LANGOPT(SemanticInterposition , 1, 0, "semantic interposition")
-BENIGN_LANGOPT(ExplicitNoSemanticInterposition, 1, 0, "explicitly no semantic interposition")
+BENIGN_LANGOPT(HalfNoSemanticInterposition, 1, 0,
+ "Like -fno-semantic-interposition but don't use local aliases")
ENUM_LANGOPT(StackProtector, StackProtectorMode, 2, SSPOff,
"stack protector mode")
ENUM_LANGOPT(TrivialAutoVarInit, TrivialAutoVarInitKind, 2, TrivialAutoVarInitKind::Uninitialized,
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index af209eb9089d..9a851f63a663 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -3793,7 +3793,7 @@ defm ipa_cp : BooleanFFlag<"ipa-cp">,
Group<clang_ignored_gcc_optimization_f_Group>;
defm ivopts : BooleanFFlag<"ivopts">, Group<clang_ignored_gcc_optimization_f_Group>;
def fsemantic_interposition : Flag<["-"], "fsemantic-interposition">, Group<f_Group>, Flags<[CC1Option]>;
-def fno_semantic_interposition: Flag<["-"], "fno-semantic-interposition">, Group<f_Group>, Flags<[CC1Option]>;
+def fno_semantic_interposition: Flag<["-"], "fno-semantic-interposition">, Group<f_Group>;
defm non_call_exceptions : BooleanFFlag<"non-call-exceptions">, Group<clang_ignored_f_Group>;
defm peel_loops : BooleanFFlag<"peel-loops">, Group<clang_ignored_gcc_optimization_f_Group>;
defm permissive : BooleanFFlag<"permissive">, Group<clang_ignored_f_Group>;
@@ -4722,6 +4722,8 @@ def pic_level : Separate<["-"], "pic-level">,
HelpText<"Value for __PIC__">;
def pic_is_pie : Flag<["-"], "pic-is-pie">,
HelpText<"File is for a position independent executable">;
+def fhalf_no_semantic_interposition : Flag<["-"], "fhalf-no-semantic-interposition">,
+ HelpText<"Like -fno-semantic-interposition but don't use local aliases">;
def fno_validate_pch : Flag<["-"], "fno-validate-pch">,
HelpText<"Disable validation of precompiled headers">,
MarshallingInfoFlag<"PreprocessorOpts->DisablePCHValidation">;
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index bf0a38bf83ab..cfc0f732748c 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -534,9 +534,6 @@ void CodeGenModule::Release() {
if (Context.getLangOpts().SemanticInterposition)
// Require various optimization to respect semantic interposition.
getModule().setSemanticInterposition(1);
- else if (Context.getLangOpts().ExplicitNoSemanticInterposition)
- // Allow dso_local on applicable targets.
- getModule().setSemanticInterposition(0);
if (CodeGenOpts.EmitCodeView) {
// Indicate that we want CodeView in the metadata.
@@ -961,15 +958,15 @@ static bool shouldAssumeDSOLocal(const CodeGenModule &CGM,
return false;
if (RM != llvm::Reloc::Static && !LOpts.PIE) {
- // On ELF, if -fno-semantic-interposition is specified, we can set dso_local
- // if using a local alias is preferable (can avoid GOT indirection).
- // Currently only x86 supports local alias.
- if (!TT.isOSBinFormatELF() ||
- !CGM.getLangOpts().ExplicitNoSemanticInterposition ||
- !GV->canBenefitFromLocalAlias())
+ // On ELF, if -fno-semantic-interposition is specified and the target
+ // supports local aliases, there will be neither CC1
+ // -fsemantic-interposition nor -fhalf-no-semantic-interposition. Set
+ // dso_local if using a local alias is preferable (can avoid GOT
+ // indirection).
+ if (!GV->canBenefitFromLocalAlias())
return false;
- // The allowed targets need to match AsmPrinter::getSymbolPreferLocal.
- return TT.isX86();
+ return !(CGM.getLangOpts().SemanticInterposition ||
+ CGM.getLangOpts().HalfNoSemanticInterposition);
}
// A definition cannot be preempted from an executable.
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 300ab6e815e2..5451244c43ae 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4561,12 +4561,31 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
CmdArgs.push_back(A->getValue());
}
- // The default is -fno-semantic-interposition. We render it just because we
- // require explicit -fno-semantic-interposition to infer dso_local.
- if (Arg *A = Args.getLastArg(options::OPT_fsemantic_interposition,
- options::OPT_fno_semantic_interposition))
- if (RelocationModel != llvm::Reloc::Static && !IsPIE)
- A->render(Args, CmdArgs);
+ // -fsemantic-interposition is forwarded to CC1: set the
+ // "SemanticInterposition" metadata to 1 (make some linkages interposable) and
+ // make default visibility external linkage definitions dso_preemptable.
+ //
+ // -fno-semantic-interposition: if the target supports .Lfoo$local local
+ // aliases (make default visibility external linkage definitions dso_local).
+ // This is the CC1 default for ELF to match COFF/Mach-O.
+ //
+ // Otherwise use Clang's traditional behavior: like
+ // -fno-semantic-interposition but local aliases are not used. So references
+ // can be interposed if not optimized out.
+ if (Triple.isOSBinFormatELF()) {
+ Arg *A = Args.getLastArg(options::OPT_fsemantic_interposition,
+ options::OPT_fno_semantic_interposition);
+ if (RelocationModel != llvm::Reloc::Static && !IsPIE) {
+ // The supported targets need to call AsmPrinter::getSymbolPreferLocal.
+ bool SupportsLocalAlias = Triple.isX86();
+ if (!A)
+ CmdArgs.push_back("-fhalf-no-semantic-interposition");
+ else if (A->getOption().matches(options::OPT_fsemantic_interposition))
+ A->render(Args, CmdArgs);
+ else if (!SupportsLocalAlias)
+ CmdArgs.push_back("-fhalf-no-semantic-interposition");
+ }
+ }
{
std::string Model;
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 06d8d2e27c9b..1d16312cf2d0 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3197,9 +3197,8 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
}
Opts.SemanticInterposition = Args.hasArg(OPT_fsemantic_interposition);
- // An explicit -fno-semantic-interposition infers dso_local.
- Opts.ExplicitNoSemanticInterposition =
- Args.hasArg(OPT_fno_semantic_interposition);
+ Opts.HalfNoSemanticInterposition =
+ Args.hasArg(OPT_fhalf_no_semantic_interposition);
// -mrtd option
if (Arg *A = Args.getLastArg(OPT_mrtd)) {
diff --git a/clang/test/CodeGen/attr-arm-sve-vector-bits-globals.c b/clang/test/CodeGen/attr-arm-sve-vector-bits-globals.c
index cb1aa6e0cf74..d81cd3627b2b 100644
--- a/clang/test/CodeGen/attr-arm-sve-vector-bits-globals.c
+++ b/clang/test/CodeGen/attr-arm-sve-vector-bits-globals.c
@@ -1,7 +1,7 @@
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
// REQUIRES: aarch64-registered-target
-// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve -target-feature +bf16 -msve-vector-bits=128 -fallow-half-arguments-and-returns -S -O1 -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK-128
-// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve -target-feature +bf16 -msve-vector-bits=512 -fallow-half-arguments-and-returns -S -O1 -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK-512
+// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve -target-feature +bf16 -msve-vector-bits=128 -fallow-half-arguments-and-returns -S -O1 -emit-llvm -o - %s -fhalf-no-semantic-interposition | FileCheck %s --check-prefix=CHECK-128
+// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -target-feature +sve -target-feature +bf16 -msve-vector-bits=512 -fallow-half-arguments-and-returns -S -O1 -emit-llvm -o - %s -fhalf-no-semantic-interposition | FileCheck %s --check-prefix=CHECK-512
#include <arm_sve.h>
diff --git a/clang/test/CodeGen/semantic-interposition-no.c b/clang/test/CodeGen/semantic-interposition-no.c
deleted file mode 100644
index cc53d1799f9d..000000000000
--- a/clang/test/CodeGen/semantic-interposition-no.c
+++ /dev/null
@@ -1,23 +0,0 @@
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -mrelocation-model pic -pic-level 1 -fno-semantic-interposition %s -o - | FileCheck %s
-
-/// For ELF -fpic/-fPIC, if -fno-semantic-interposition is specified, mark
-/// defined variables and functions dso_local. ifunc isn't marked.
-
-// CHECK: @var = dso_local global i32 0, align 4
-// CHECK: @ext_var = external global i32, align 4
-int var;
-extern int ext_var;
-
-// CHECK: @ifunc = ifunc i32 (), bitcast (i8* ()* @ifunc_resolver to i32 ()*)
-int ifunc(void) __attribute__((ifunc("ifunc_resolver")));
-
-// CHECK: define dso_local i32 @func()
-// CHECK: declare i32 @ext()
-int func(void) { return 0; }
-int ext(void);
-
-static void *ifunc_resolver() { return func; }
-
-int foo() {
- return var + ext_var + ifunc() + func() + ext();
-}
diff --git a/clang/test/CodeGen/semantic-interposition.c b/clang/test/CodeGen/semantic-interposition.c
index 3d6c5f2872b5..6b402214df9c 100644
--- a/clang/test/CodeGen/semantic-interposition.c
+++ b/clang/test/CodeGen/semantic-interposition.c
@@ -1,9 +1,38 @@
-// RUN: %clang_cc1 -emit-llvm -fsemantic-interposition %s -o - | FileCheck --check-prefix=INTERPOSITION %s
-// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck --check-prefix=NO %s
-/// With explicit -fno-semantic-interposition, add a module flag to inform the
-/// backend that dso_local can be inferred.
-// RUN: %clang_cc1 -emit-llvm -fno-semantic-interposition %s -o - | FileCheck --check-prefix=EXPLICIT_NO %s
-
-// INTERPOSITION: !{{[0-9]+}} = !{i32 1, !"SemanticInterposition", i32 1}
-// NO-NOT: "SemanticInterposition"
-// EXPLICIT_NO: !{{[0-9]+}} = !{i32 1, !"SemanticInterposition", i32 0}
+/// -fno-semantic-interposition is the default and local aliases (via dso_local) are allowed.
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -mrelocation-model pic -pic-level 1 %s -o - | FileCheck %s --check-prefixes=CHECK,NOMETADATA
+
+/// -fsemantic-interposition sets a module metadata.
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -mrelocation-model pic -pic-level 1 -fsemantic-interposition %s -o - | FileCheck %s --check-prefixes=PREEMPT,METADATA
+
+/// Traditional half-baked behavior: interprocedural optimizations are allowed
+/// but local aliases are not used.
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -mrelocation-model pic -pic-level 1 -fhalf-no-semantic-interposition %s -o - | FileCheck %s --check-prefixes=PREEMPT,NOMETADATA
+
+// CHECK: @var = dso_local global i32 0, align 4
+// CHECK: @ext_var = external global i32, align 4
+// CHECK: @ifunc = ifunc i32 (), bitcast (i8* ()* @ifunc_resolver to i32 ()*)
+// CHECK: define dso_local i32 @func()
+// CHECK: declare i32 @ext()
+
+// PREEMPT: @var = global i32 0, align 4
+// PREEMPT: @ext_var = external global i32, align 4
+// PREEMPT: @ifunc = ifunc i32 (), bitcast (i8* ()* @ifunc_resolver to i32 ()*)
+// PREEMPT: define i32 @func()
+// PREEMPT: declare i32 @ext()
+
+// METADATA: !{{[0-9]+}} = !{i32 1, !"SemanticInterposition", i32 1}
+// NOMETADATA-NOT: "SemanticInterposition"
+
+int var;
+extern int ext_var;
+
+int ifunc(void) __attribute__((ifunc("ifunc_resolver")));
+
+int func(void) { return 0; }
+int ext(void);
+
+static void *ifunc_resolver() { return func; }
+
+int foo() {
+ return var + ext_var + ifunc() + func() + ext();
+}
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/child-inheritted-from-parent-in-comdat.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/child-inheritted-from-parent-in-comdat.cpp
index 631594c2897d..9e9a35a4a60a 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/child-inheritted-from-parent-in-comdat.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/child-inheritted-from-parent-in-comdat.cpp
@@ -1,7 +1,7 @@
// Cross comdat example
// Parent VTable is in a comdat section.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
// The inline function is emitted in each module with the same comdat
// CHECK: $_ZTS1A = comdat any
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-1.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-1.cpp
index 3a7f65a72656..381eb246a3ba 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-1.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-1.cpp
@@ -1,7 +1,7 @@
// Check the vtable layout for classes with key functions defined in
diff erent
// translation units. This TU only manifests the vtable for A.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
#include "cross-tu-header.h"
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-2.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-2.cpp
index 10c87ea1a672..dafe7d57dea0 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-2.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/cross-translation-unit-2.cpp
@@ -1,7 +1,7 @@
// Check the vtable layout for classes with key functions defined in
diff erent
// translation units. This TU manifests the vtable for B.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
#include "cross-tu-header.h"
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/diamond-inheritance.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/diamond-inheritance.cpp
index e42e402ec0a4..03165ddb0282 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/diamond-inheritance.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/diamond-inheritance.cpp
@@ -1,7 +1,7 @@
// Diamond inheritance.
// A more complicated multiple inheritance example that includes longer chain of inheritance and a common ancestor.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
// CHECK-DAG: %class.B = type { %class.A }
// CHECK-DAG: %class.A = type { i32 (...)** }
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/diamond-virtual-inheritance.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/diamond-virtual-inheritance.cpp
index 0fff28ab8a09..af6c36222534 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/diamond-virtual-inheritance.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/diamond-virtual-inheritance.cpp
@@ -1,7 +1,7 @@
// Diamond virtual inheritance.
// This should cover virtual inheritance, construction vtables, and VTTs.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
// Class A contains a vtable ptr, then int, then padding
// CHECK-DAG: %class.B = type { i32 (...)**, %class.A.base }
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/inheritted-virtual-function.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/inheritted-virtual-function.cpp
index 4622970823f4..7c9da5d333cb 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/inheritted-virtual-function.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/inheritted-virtual-function.cpp
@@ -1,7 +1,7 @@
// Check the layout of the vtable for a child class that inherits a virtual
// function but does not override it.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
class A {
public:
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/inline-virtual-function.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/inline-virtual-function.cpp
index 900e9429bc7e..77f666dec1ee 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/inline-virtual-function.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/inline-virtual-function.cpp
@@ -1,8 +1,8 @@
// The VTable is not in a comdat but the inline methods are.
// This doesn’t affect the vtable or the stubs we emit.
-// RUN: %clang_cc1 %s -triple=aarch64 -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
-// RUN: %clang_cc1 %s -triple=x86_64 -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64 -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
+// RUN: %clang_cc1 %s -triple=x86_64 -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
// CHECK: $_ZTI1A.rtti_proxy = comdat any
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/multiple-inheritance.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/multiple-inheritance.cpp
index 8d888e69ed62..547bac85dafe 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/multiple-inheritance.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/multiple-inheritance.cpp
@@ -1,6 +1,6 @@
// Multiple inheritance.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
// CHECK: %class.C = type { %class.A, %class.B }
// CHECK: %class.A = type { i32 (...)** }
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/no-alias-when-dso-local.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/no-alias-when-dso-local.cpp
index 8e04df39e64e..89fe6da2a4e4 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/no-alias-when-dso-local.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/no-alias-when-dso-local.cpp
@@ -1,7 +1,7 @@
// Check that no alias is emitted when the vtable is already dso_local. This can
// happen if the class is hidden.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s --check-prefix=DEFAULT-VIS
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s --check-prefix=DEFAULT-VIS
// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fvisibility hidden | FileCheck %s --check-prefix=HIDDEN-VIS
// DEFAULT-VIS: @_ZTV1A.local = private unnamed_addr constant
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/override-pure-virtual-method.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/override-pure-virtual-method.cpp
index 0d894ac899ff..2a1ecf567d86 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/override-pure-virtual-method.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/override-pure-virtual-method.cpp
@@ -2,7 +2,7 @@
// We instead emit zero for the pure virtual function component. See PR43094 for
// details.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
// CHECK: @_ZTV1A.local = private unnamed_addr constant { [4 x i32] } { [4 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint ({ i8*, i8* }** @_ZTI1A.rtti_proxy to i64), i64 ptrtoint (i32* getelementptr inbounds ({ [4 x i32] }, { [4 x i32] }* @_ZTV1A.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 0, i32 trunc (i64 sub (i64 ptrtoint (void (%class.A*)* dso_local_equivalent @_ZN1A3barEv to i64), i64 ptrtoint (i32* getelementptr inbounds ({ [4 x i32] }, { [4 x i32] }* @_ZTV1A.local, i32 0, i32 0, i32 2) to i64)) to i32)] }, align 4
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/overriden-virtual-function.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/overriden-virtual-function.cpp
index 95e9c44706d0..4ec08d7eee74 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/overriden-virtual-function.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/overriden-virtual-function.cpp
@@ -1,7 +1,7 @@
// Check the layout of the vtable for a child class that inherits a virtual
// function but does override it.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
// CHECK: @_ZTV1B.local = private unnamed_addr constant { [4 x i32] } { [4 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint ({ i8*, i8*, i8* }** @_ZTI1B.rtti_proxy to i64), i64 ptrtoint (i32* getelementptr inbounds ({ [4 x i32] }, { [4 x i32] }* @_ZTV1B.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (void (%class.B*)* dso_local_equivalent @_ZN1B3fooEv to i64), i64 ptrtoint (i32* getelementptr inbounds ({ [4 x i32] }, { [4 x i32] }* @_ZTV1B.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (void (%class.B*)* dso_local_equivalent @_ZN1B3barEv to i64), i64 ptrtoint (i32* getelementptr inbounds ({ [4 x i32] }, { [4 x i32] }* @_ZTV1B.local, i32 0, i32 0, i32 2) to i64)) to i32)] }, align 4
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/relative-vtables-flag.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/relative-vtables-flag.cpp
index 57ff203f16f4..b141b2faec45 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/relative-vtables-flag.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/relative-vtables-flag.cpp
@@ -3,7 +3,7 @@
// of a soft incremental rollout. This ABI should only be used if the flag for
// it is passed on Fuchsia.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck --check-prefix=RELATIVE-ABI %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck --check-prefix=RELATIVE-ABI %s
// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -S -o - -emit-llvm -fno-experimental-relative-c++-abi-vtables | FileCheck --check-prefix=DEFAULT-ABI %s
// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -S -o - -emit-llvm | FileCheck --check-prefix=DEFAULT-ABI %s
diff --git a/clang/test/CodeGenCXX/RelativeVTablesABI/simple-vtable-definition.cpp b/clang/test/CodeGenCXX/RelativeVTablesABI/simple-vtable-definition.cpp
index 29a02b57226b..c9dee26b77ce 100644
--- a/clang/test/CodeGenCXX/RelativeVTablesABI/simple-vtable-definition.cpp
+++ b/clang/test/CodeGenCXX/RelativeVTablesABI/simple-vtable-definition.cpp
@@ -1,6 +1,6 @@
// Check the layout of the vtable for a normal class.
-// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
+// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
// We should be emitting comdats for each of the virtual function RTTI proxies
// CHECK: $_ZTI1A.rtti_proxy = comdat any
diff --git a/clang/test/Driver/fsemantic-interposition.c b/clang/test/Driver/fsemantic-interposition.c
index af3e7575a799..af76daf7e1be 100644
--- a/clang/test/Driver/fsemantic-interposition.c
+++ b/clang/test/Driver/fsemantic-interposition.c
@@ -2,12 +2,27 @@
// RUN: %clang -target x86_64 %s -Werror -fPIC -fsemantic-interposition -c -### 2>&1 | FileCheck %s
// CHECK: "-fsemantic-interposition"
-/// Require explicit -fno-semantic-interposition to infer dso_local.
-// RUN: %clang -target x86_64 %s -Werror -fPIC -fsemantic-interposition -fno-semantic-interposition -c -### 2>&1 | FileCheck --check-prefix=EXPLICIT_NO %s
-// EXPLICIT_NO: "-fno-semantic-interposition"
+/// No-op for -fno-pic/-fpie.
+// RUN: %clang -target x86_64 %s -Werror -fsemantic-interposition -c -### 2>&1 | FileCheck --check-prefix=NOOP %s
+// RUN: %clang -target x86_64 %s -Werror -fPIE -fsemantic-interposition -c -### 2>&1 | FileCheck --check-prefix=NOOP %s
+// NOOP-NOT: "-fsemantic-interposition"
+// NOOP-NOT: "-fno-semantic-interposition"
-// RUN: %clang -target x86_64 %s -Werror -fsemantic-interposition -c -### 2>&1 | FileCheck --check-prefix=NO %s
-// RUN: %clang -target x86_64 %s -Werror -fPIC -c -### 2>&1 | FileCheck --check-prefix=NO %s
-// RUN: %clang -target x86_64 %s -Werror -fPIE -fsemantic-interposition -c -### 2>&1 | FileCheck --check-prefix=NO %s
+/// If -fno-semantic-interposition is specified and the target supports local
+/// aliases, neither CC1 option is set.
+// RUN: %clang -target i386 %s -Werror -fPIC -fno-semantic-interposition -c -### 2>&1 | FileCheck --check-prefix=NO %s
+// RUN: %clang -target x86_64 %s -Werror -fPIC -fno-semantic-interposition -c -### 2>&1 | FileCheck --check-prefix=NO %s
// NO-NOT: "-fsemantic-interposition"
-// NO-NOT: "-fno-semantic-interposition"
+// NO-NOT: "-fhalf-no-semantic-interposition"
+
+/// If neither -fsemantic-interposition or -fno-semantic-interposition is specified,
+/// or -fno-semantic-interposition is specified but the target does not support
+/// local aliases, use the traditional half-baked behavor: interprocedural
+/// optimizations are allowed but local aliases are not used. If references are
+/// not optimized out, semantic interposition at runtime is possible.
+// RUN: %clang -target aarch64 %s -Werror -fPIC -fno-semantic-interposition -c -### 2>&1 | FileCheck --check-prefix=HALF %s
+// RUN: %clang -target ppc64le %s -Werror -fPIC -fno-semantic-interposition -c -### 2>&1 | FileCheck --check-prefix=HALF %s
+
+// RUN: %clang -target x86_64 %s -Werror -fPIC -c -### 2>&1 | FileCheck --check-prefix=HALF %s
+//
+// HALF: "-fhalf-no-semantic-interposition"
diff --git a/llvm/include/llvm/IR/Module.h b/llvm/include/llvm/IR/Module.h
index 2ec6f962e443..3664b275114d 100644
--- a/llvm/include/llvm/IR/Module.h
+++ b/llvm/include/llvm/IR/Module.h
@@ -855,7 +855,6 @@ class Module {
/// Returns whether semantic interposition is to be respected.
bool getSemanticInterposition() const;
- bool noSemanticInterposition() const;
/// Set whether semantic interposition is to be respected.
void setSemanticInterposition(bool);
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 7f7ea18e72b8..6732c35e2094 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -483,10 +483,8 @@ MCSymbol *AsmPrinter::getSymbolPreferLocal(const GlobalValue &GV) const {
if (TM.getTargetTriple().isOSBinFormatELF() && GV.canBenefitFromLocalAlias()) {
const Module &M = *GV.getParent();
if (TM.getRelocationModel() != Reloc::Static &&
- M.getPIELevel() == PIELevel::Default)
- if (GV.isDSOLocal() || (TM.getTargetTriple().isX86() &&
- GV.getParent()->noSemanticInterposition()))
- return getSymbolWithGlobalValueBase(&GV, "$local");
+ M.getPIELevel() == PIELevel::Default && GV.isDSOLocal())
+ return getSymbolWithGlobalValueBase(&GV, "$local");
}
return TM.getSymbol(&GV);
}
diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp
index b6fde57c70d0..b4f10e2e2d23 100644
--- a/llvm/lib/IR/Module.cpp
+++ b/llvm/lib/IR/Module.cpp
@@ -601,13 +601,6 @@ void Module::setSemanticInterposition(bool SI) {
addModuleFlag(ModFlagBehavior::Error, "SemanticInterposition", SI);
}
-bool Module::noSemanticInterposition() const {
- // Conservatively require an explicit zero value for now.
- Metadata *MF = getModuleFlag("SemanticInterposition");
- auto *Val = cast_or_null<ConstantAsMetadata>(MF);
- return Val && cast<ConstantInt>(Val->getValue())->getZExtValue() == 0;
-}
-
void Module::setOwnedMemoryBuffer(std::unique_ptr<MemoryBuffer> MB) {
OwnedMemoryBuffer = std::move(MB);
}
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