nruslan created this revision.
nruslan added reviewers: hans, craig.topper.
Herald added a subscriber: cfe-commits.
Allows to disable direct TLS segment access (%fs or %gs). GCC supports a
similar flag, it can be useful in some circumstances, e.g. when a thread
context block needs to be updated directly from user space. More info and
specific use cases: https://bugs.llvm.org/show_bug.cgi?id=16145
There is another revision for LLVM as well.
Repository:
rC Clang
https://reviews.llvm.org/D53102
Files:
docs/ClangCommandLineReference.rst
include/clang/Driver/CC1Options.td
include/clang/Driver/Options.td
include/clang/Frontend/CodeGenOptions.def
lib/CodeGen/CGCall.cpp
lib/Driver/ToolChains/Clang.cpp
lib/Frontend/CompilerInvocation.cpp
test/CodeGen/indirect-tls-seg-refs.c
test/Driver/indirect-tls-seg-refs.c
Index: test/Driver/indirect-tls-seg-refs.c
===================================================================
--- /dev/null
+++ test/Driver/indirect-tls-seg-refs.c
@@ -0,0 +1,7 @@
+// RUN: %clang -### %s 2>&1 | FileCheck %s -check-prefix=TLSDIRECT
+// RUN: %clang -### -mno-tls-direct-seg-refs -mtls-direct-seg-refs %s 2>&1 | FileCheck %s -check-prefix=TLSDIRECT
+// RUN: %clang -### -mtls-direct-seg-refs -mno-tls-direct-seg-refs %s 2>&1 | FileCheck %s -check-prefix=NO-TLSDIRECT
+// REQUIRES: clang-driver
+
+// NO-TLSDIRECT: -indirect-tls-seg-refs
+// TLSDIRECT-NOT: -indirect-tls-seg-refs
Index: test/CodeGen/indirect-tls-seg-refs.c
===================================================================
--- /dev/null
+++ test/CodeGen/indirect-tls-seg-refs.c
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 %s -emit-llvm -o - -indirect-tls-seg-refs | FileCheck %s -check-prefix=NO-TLSDIRECT
+// RUN: %clang_cc1 %s -emit-llvm -o - | FileCheck %s -check-prefix=TLSDIRECT
+
+// NO-TLSDIRECT: attributes #{{[0-9]+}} = {{{.*}} "indirect-tls-seg-refs"
+// TLSDIRECT-NOT: attributes #{{[0-9]+}} = {{{.*}} "indirect-tls-seg-refs"
+
+void test1() {
+}
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -614,6 +614,7 @@
Opts.DisableLifetimeMarkers = Args.hasArg(OPT_disable_lifetimemarkers);
Opts.DisableO0ImplyOptNone = Args.hasArg(OPT_disable_O0_optnone);
Opts.DisableRedZone = Args.hasArg(OPT_disable_red_zone);
+ Opts.IndirectTlsSegRefs = Args.hasArg(OPT_indirect_tls_seg_refs);
Opts.ForbidGuardVariables = Args.hasArg(OPT_fforbid_guard_variables);
Opts.UseRegisterSizedBitfieldAccess = Args.hasArg(
OPT_fuse_register_sized_bitfield_access);
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -1739,6 +1739,10 @@
Args.hasArg(options::OPT_fapple_kext))
CmdArgs.push_back("-disable-red-zone");
+ if (!Args.hasFlag(options::OPT_mtls_direct_seg_refs,
+ options::OPT_mno_tls_direct_seg_refs, true))
+ CmdArgs.push_back("-indirect-tls-seg-refs");
+
// Default to avoid implicit floating-point for kernel/kext code, but allow
// that to be overridden with -mno-soft-float.
bool NoImplicitFloat = (Args.hasArg(options::OPT_mkernel) ||
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -1709,6 +1709,8 @@
if (CodeGenOpts.DisableRedZone)
FuncAttrs.addAttribute(llvm::Attribute::NoRedZone);
+ if (CodeGenOpts.IndirectTlsSegRefs)
+ FuncAttrs.addAttribute("indirect-tls-seg-refs");
if (CodeGenOpts.NoImplicitFloat)
FuncAttrs.addAttribute(llvm::Attribute::NoImplicitFloat);
Index: include/clang/Frontend/CodeGenOptions.def
===================================================================
--- include/clang/Frontend/CodeGenOptions.def
+++ include/clang/Frontend/CodeGenOptions.def
@@ -62,6 +62,8 @@
CODEGENOPT(DebugPassManager, 1, 0) ///< Prints debug information for the new
///< pass manager.
CODEGENOPT(DisableRedZone , 1, 0) ///< Set when -mno-red-zone is enabled.
+CODEGENOPT(IndirectTlsSegRefs, 1, 0) ///< Set when -mno-tls-direct-seg-refs
+ ///< is specified.
CODEGENOPT(DisableTailCalls , 1, 0) ///< Do not emit tail calls.
CODEGENOPT(NoEscapingBlockTailCalls, 1, 0) ///< Do not emit tail calls from
///< escaping blocks.
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -2006,6 +2006,8 @@
def mno_pascal_strings : Flag<["-"], "mno-pascal-strings">,
Alias<fno_pascal_strings>;
def mno_red_zone : Flag<["-"], "mno-red-zone">, Group<m_Group>;
+def mno_tls_direct_seg_refs : Flag<["-"], "mno-tls-direct-seg-refs">, Group<m_Group>,
+ HelpText<"Disable direct TLS access through segment registers">;
def mno_relax_all : Flag<["-"], "mno-relax-all">, Group<m_Group>;
def mno_rtd: Flag<["-"], "mno-rtd">, Group<m_Group>;
def mno_soft_float : Flag<["-"], "mno-soft-float">, Group<m_Group>;
@@ -2161,6 +2163,8 @@
def moslib_EQ : Joined<["-"], "moslib=">, Group<m_Group>;
def mpascal_strings : Flag<["-"], "mpascal-strings">, Alias<fpascal_strings>;
def mred_zone : Flag<["-"], "mred-zone">, Group<m_Group>;
+def mtls_direct_seg_refs : Flag<["-"], "mtls-direct-seg-refs">, Group<m_Group>,
+ HelpText<"Enable direct TLS access through segment registers">;
def mregparm_EQ : Joined<["-"], "mregparm=">, Group<m_Group>;
def mrelax_all : Flag<["-"], "mrelax-all">, Group<m_Group>, Flags<[CC1Option,CC1AsOption]>,
HelpText<"(integrated-as) Relax all machine instructions">;
Index: include/clang/Driver/CC1Options.td
===================================================================
--- include/clang/Driver/CC1Options.td
+++ include/clang/Driver/CC1Options.td
@@ -192,6 +192,8 @@
HelpText<"Disable adding the optnone attribute to functions at O0">;
def disable_red_zone : Flag<["-"], "disable-red-zone">,
HelpText<"Do not emit code that uses the red zone.">;
+def indirect_tls_seg_refs : Flag<["-"], "indirect-tls-seg-refs">,
+ HelpText<"Do not emit code that uses direct TLS segment access.">;
def dwarf_column_info : Flag<["-"], "dwarf-column-info">,
HelpText<"Turn on column location information.">;
def split_dwarf : Flag<["-"], "split-dwarf">,
Index: docs/ClangCommandLineReference.rst
===================================================================
--- docs/ClangCommandLineReference.rst
+++ docs/ClangCommandLineReference.rst
@@ -2236,6 +2236,10 @@
.. option:: -mred-zone, -mno-red-zone
+.. option:: -mtls-direct-seg-refs, -mno-tls-direct-seg-refs
+
+Enable or disable direct TLS access through segment registers
+
.. option:: -mregparm=<arg>
.. option:: -mrelax-all, -mno-relax-all
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