[clang] [sframe] Add assembler option --gsframe (PR #165322)
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Mon Oct 27 14:41:03 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: None (Sterling-Augustine)
<details>
<summary>Changes</summary>
This plumbs the option --gsframe through the various levels needed to support it in the assembler.
This is the final step in assembler-level sframe support for x86. With it in place, clang produces sframe-sections that successfully link with gnu-ld.
LLD support is pending some discussion.
---
Full diff: https://github.com/llvm/llvm-project/pull/165322.diff
5 Files Affected:
- (modified) clang/include/clang/Basic/CodeGenOptions.def (+2)
- (modified) clang/include/clang/Driver/Options.td (+12-5)
- (modified) clang/lib/CodeGen/BackendUtil.cpp (+1)
- (modified) clang/lib/Driver/ToolChains/Clang.cpp (+12)
- (modified) clang/tools/driver/cc1as_main.cpp (+6)
``````````diff
diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index 90e1f8d1eb5e9..99199c3a6c34c 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -120,6 +120,8 @@ CODEGENOPT(StackSizeSection , 1, 0, Benign) ///< Set when -fstack-size-section
///< Set when -femit-compact-unwind-non-canonical is enabled.
CODEGENOPT(EmitCompactUnwindNonCanonical, 1, 0, Benign)
+CODEGENOPT(EmitSFrameUnwind, 1, 0, Benign) ///< Set when -sframe is enabled.
+
///< Set when -fxray-always-emit-customevents is enabled.
CODEGENOPT(XRayAlwaysEmitCustomEvents , 1, 0, Benign)
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 93aeb22b18e92..06365cef77bf0 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4701,11 +4701,13 @@ def femit_dwarf_unwind_EQ : Joined<["-"], "femit-dwarf-unwind=">,
NormalizedValues<["Always", "NoCompactUnwind", "Default"]>,
NormalizedValuesScope<"llvm::EmitDwarfUnwindType">,
MarshallingInfoEnum<CodeGenOpts<"EmitDwarfUnwind">, "Default">;
-defm emit_compact_unwind_non_canonical : BoolFOption<"emit-compact-unwind-non-canonical",
- CodeGenOpts<"EmitCompactUnwindNonCanonical">, DefaultFalse,
- PosFlag<SetTrue, [], [ClangOption, CC1Option, CC1AsOption],
- "Try emitting Compact-Unwind for non-canonical entries. Maybe overridden by other constraints">,
- NegFlag<SetFalse>>;
+defm emit_compact_unwind_non_canonical
+ : BoolFOption<"emit-compact-unwind-non-canonical",
+ CodeGenOpts<"EmitCompactUnwindNonCanonical">, DefaultFalse,
+ PosFlag<SetTrue, [], [ClangOption, CC1Option, CC1AsOption],
+ "Try emitting Compact-Unwind for non-canonical "
+ "entries. Maybe overridden by other constraints">,
+ NegFlag<SetFalse>>;
def g_Flag : Flag<["-"], "g">, Group<g_Group>,
Visibility<[ClangOption, CLOption, DXCOption, FlangOption]>,
HelpText<"Generate source-level debug information">;
@@ -7729,6 +7731,11 @@ def massembler_fatal_warnings : Flag<["-"], "massembler-fatal-warnings">,
def crel : Flag<["--"], "crel">,
HelpText<"Enable CREL relocation format (ELF only)">,
MarshallingInfoFlag<CodeGenOpts<"Crel">>;
+// The leading 'g' is misleading. This is an unwind tables option, not
+// a debug option. But uses this name for gnu compatibility.
+def gsframe : Flag<["--"], "gsframe">,
+ HelpText<"Generate .sframe unwind sections (ELF only)">,
+ MarshallingInfoFlag<CodeGenOpts<"EmitSFrameUnwind">>;
def mmapsyms_implicit : Flag<["-"], "mmapsyms=implicit">,
HelpText<"Allow mapping symbol at section beginning to be implicit, "
"lowering number of mapping symbols at the expense of some "
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 468c930acacbd..4b988103e3cd1 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -500,6 +500,7 @@ static bool initTargetOptions(const CompilerInstance &CI,
Options.MCOptions.EmitDwarfUnwind = CodeGenOpts.getEmitDwarfUnwind();
Options.MCOptions.EmitCompactUnwindNonCanonical =
CodeGenOpts.EmitCompactUnwindNonCanonical;
+ Options.MCOptions.EmitSFrameUnwind = CodeGenOpts.EmitSFrameUnwind;
Options.MCOptions.MCRelaxAll = CodeGenOpts.RelaxAll;
Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
Options.MCOptions.MCUseDwarfDirectory =
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 79edc561c551f..a033e8f708306 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -2617,6 +2617,8 @@ static void CollectArgsForIntegratedAssembler(Compilation &C,
llvm::codegenoptions::DebugInfoConstructor,
DwarfVersion, llvm::DebuggerKind::Default);
}
+ } else if (Value == "--gsframe") {
+ CmdArgs.push_back("--gsframe");
} else if (Value.starts_with("-mcpu") || Value.starts_with("-mfpu") ||
Value.starts_with("-mhwdiv") || Value.starts_with("-march")) {
// Do nothing, we'll validate it later.
@@ -5920,6 +5922,16 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
else if (UnwindTables)
CmdArgs.push_back("-funwind-tables=1");
+ // Sframe unwind tables are independent of the other types, and only defined
+ // for these two targets.
+ if (Arg *A = Args.getLastArg(options::OPT_gsframe)) {
+ if ((Triple.isAArch64() || Triple.isX86()) && Triple.isOSBinFormatELF())
+ CmdArgs.push_back("--gsframe");
+ else
+ D.Diag(diag::err_drv_unsupported_opt_for_target)
+ << A->getOption().getName() << TripleStr;
+ }
+
// Prepare `-aux-target-cpu` and `-aux-target-feature` unless
// `--gpu-use-aux-triple-only` is specified.
if (!Args.getLastArg(options::OPT_gpu_use_aux_triple_only) &&
diff --git a/clang/tools/driver/cc1as_main.cpp b/clang/tools/driver/cc1as_main.cpp
index 50da2f8449a22..3187a5b5c571b 100644
--- a/clang/tools/driver/cc1as_main.cpp
+++ b/clang/tools/driver/cc1as_main.cpp
@@ -163,6 +163,10 @@ struct AssemblerInvocation {
LLVM_PREFERRED_TYPE(bool)
unsigned EmitCompactUnwindNonCanonical : 1;
+ // Whether to emit sframe unwind sections.
+ LLVM_PREFERRED_TYPE(bool)
+ unsigned EmitSFrameUnwind : 1;
+
LLVM_PREFERRED_TYPE(bool)
unsigned Crel : 1;
LLVM_PREFERRED_TYPE(bool)
@@ -388,6 +392,7 @@ bool AssemblerInvocation::CreateFromArgs(AssemblerInvocation &Opts,
Opts.EmitCompactUnwindNonCanonical =
Args.hasArg(OPT_femit_compact_unwind_non_canonical);
+ Opts.EmitSFrameUnwind = Args.hasArg(OPT_gsframe);
Opts.Crel = Args.hasArg(OPT_crel);
Opts.ImplicitMapsyms = Args.hasArg(OPT_mmapsyms_implicit);
Opts.X86RelaxRelocations = !Args.hasArg(OPT_mrelax_relocations_no);
@@ -450,6 +455,7 @@ static bool ExecuteAssemblerImpl(AssemblerInvocation &Opts,
MCOptions.MCRelaxAll = Opts.RelaxAll;
MCOptions.EmitDwarfUnwind = Opts.EmitDwarfUnwind;
MCOptions.EmitCompactUnwindNonCanonical = Opts.EmitCompactUnwindNonCanonical;
+ MCOptions.EmitSFrameUnwind = Opts.EmitSFrameUnwind;
MCOptions.MCSaveTempLabels = Opts.SaveTemporaryLabels;
MCOptions.Crel = Opts.Crel;
MCOptions.ImplicitMapSyms = Opts.ImplicitMapsyms;
``````````
</details>
https://github.com/llvm/llvm-project/pull/165322
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