[flang-commits] [flang] bc0c028 - [Flang][Driver] Add support for option -f[no-]split-machine-functions in flang (#216637)
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Wed Aug 19 23:48:29 PDT 2026
Author: Kaviya Rajendiran
Date: 2026-08-20T12:18:22+05:30
New Revision: bc0c028fa5a3e8a76bc432f5b22d1ee4883acaca
URL: https://github.com/llvm/llvm-project/commit/bc0c028fa5a3e8a76bc432f5b22d1ee4883acaca
DIFF: https://github.com/llvm/llvm-project/commit/bc0c028fa5a3e8a76bc432f5b22d1ee4883acaca.diff
LOG: [Flang][Driver] Add support for option -f[no-]split-machine-functions in flang (#216637)
Added support for the `-fsplit-machine-functions` flag in the
Flang driver.
- The Flang driver forwards `-fsplit-machine-functions` to `-fc1` and
the negative flag `-fno-split-machine-functions` is used at the driver
level only.
- Flang `-fc1` driver sets `TargetOptions.EnableMachineFunctionSplitter`,
which causes LLVM's MachineFunctionSplitterPass to be added to the
codegen pipeline
Added:
flang/test/Driver/fsplit-machine-functions.f90
flang/test/Driver/split-machine-function-pass.f90
Modified:
clang/include/clang/Driver/CommonArgs.h
clang/include/clang/Options/Options.td
clang/lib/Driver/ToolChains/Clang.cpp
clang/lib/Driver/ToolChains/CommonArgs.cpp
clang/lib/Driver/ToolChains/Flang.cpp
flang/include/flang/Frontend/TargetOptions.h
flang/lib/Frontend/CompilerInstance.cpp
flang/lib/Frontend/CompilerInvocation.cpp
Removed:
################################################################################
diff --git a/clang/include/clang/Driver/CommonArgs.h b/clang/include/clang/Driver/CommonArgs.h
index 3b53df94fc79f..be15d15a1661e 100644
--- a/clang/include/clang/Driver/CommonArgs.h
+++ b/clang/include/clang/Driver/CommonArgs.h
@@ -257,6 +257,11 @@ void addMachineOutlinerArgs(const Driver &D, const llvm::opt::ArgList &Args,
const llvm::Triple &Triple, bool IsLTO,
const StringRef PluginOptPrefix = "");
+void addSplitMachineFunctionsArgs(const Driver &D,
+ const llvm::opt::ArgList &Args,
+ llvm::opt::ArgStringList &CmdArgs,
+ const llvm::Triple &Triple);
+
void addOpenMPDeviceRTL(const Driver &D, const llvm::opt::ArgList &DriverArgs,
llvm::opt::ArgStringList &CC1Args,
StringRef BitcodeSuffix, const llvm::Triple &Triple,
diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td
index adc4224dd561c..7eacbc7a44827 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -5068,8 +5068,8 @@ defm separate_named_sections : BoolFOption<"separate-named-sections",
defm split_machine_functions: BoolFOption<"split-machine-functions",
CodeGenOpts<"SplitMachineFunctions">, DefaultFalse,
- PosFlag<SetTrue, [], [ClangOption, CC1Option], "Enable">,
- NegFlag<SetFalse, [], [ClangOption], "Disable">,
+ PosFlag<SetTrue, [], [ClangOption, CC1Option, FlangOption, FC1Option], "Enable">,
+ NegFlag<SetFalse, [], [ClangOption, FlangOption], "Disable">,
BothFlags<[], [ClangOption], " late function splitting using profile information (x86 and aarch64 ELF)">>;
defm partition_static_data_sections: BoolFOption<"partition-static-data-sections",
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 54583fe3abbd8..ccc226eff0782 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -6618,17 +6618,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
Args.addOptInFlag(CmdArgs, options::OPT_funique_basic_block_section_names,
options::OPT_fno_unique_basic_block_section_names);
- if (Arg *A = Args.getLastArg(options::OPT_fsplit_machine_functions,
- options::OPT_fno_split_machine_functions)) {
- if (!A->getOption().matches(options::OPT_fno_split_machine_functions)) {
- // This codegen pass is only available on x86 and AArch64 ELF targets.
- if ((Triple.isX86() || Triple.isAArch64()) && Triple.isOSBinFormatELF())
- A->render(Args, CmdArgs);
- else
- D.Diag(diag::err_drv_unsupported_opt_for_target)
- << A->getAsString(Args) << TripleStr;
- }
- }
+ addSplitMachineFunctionsArgs(D, Args, CmdArgs, Triple);
if (Arg *A =
Args.getLastArg(options::OPT_fpartition_static_data_sections,
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index e1c07fb94ea76..7db070699b23f 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -3086,6 +3086,23 @@ void tools::addMachineOutlinerArgs(const Driver &D,
addArg(Twine("-codegen-data-use-path=") + CodeGenDataUseArg->getValue());
}
+void tools::addSplitMachineFunctionsArgs(const Driver &D,
+ const llvm::opt::ArgList &Args,
+ llvm::opt::ArgStringList &CmdArgs,
+ const llvm::Triple &Triple) {
+ if (Arg *A = Args.getLastArg(options::OPT_fsplit_machine_functions,
+ options::OPT_fno_split_machine_functions)) {
+ if (!A->getOption().matches(options::OPT_fno_split_machine_functions)) {
+ // This codegen pass is only available on x86 and AArch64 ELF targets.
+ if ((Triple.isX86() || Triple.isAArch64()) && Triple.isOSBinFormatELF())
+ A->render(Args, CmdArgs);
+ else
+ D.Diag(diag::err_drv_unsupported_opt_for_target)
+ << A->getAsString(Args) << Triple.getTriple();
+ }
+ }
+}
+
void tools::addOpenMPDeviceRTL(const Driver &D,
const llvm::opt::ArgList &DriverArgs,
llvm::opt::ArgStringList &CC1Args,
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index a40540691a254..5824f59400323 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -1233,6 +1233,8 @@ static void addPGOAndCoverageFlags(const ToolChain &TC, const JobAction &JA,
if (Args.hasFlag(options::OPT_fpseudo_probe_for_profiling,
options::OPT_fno_pseudo_probe_for_profiling, false))
CmdArgs.push_back("-fpseudo-probe-for-profiling");
+
+ addSplitMachineFunctionsArgs(TC.getDriver(), Args, CmdArgs, TC.getTriple());
}
void Flang::ConstructJob(Compilation &C, const JobAction &JA,
diff --git a/flang/include/flang/Frontend/TargetOptions.h b/flang/include/flang/Frontend/TargetOptions.h
index f6e5634d5a995..fc7a2a3089f15 100644
--- a/flang/include/flang/Frontend/TargetOptions.h
+++ b/flang/include/flang/Frontend/TargetOptions.h
@@ -54,6 +54,9 @@ class TargetOptions {
/// Print verbose assembly
bool asmVerbose = false;
+ /// Enable splitting of machine functions using profile information.
+ bool SplitMachineFunctions = false;
+
/// Atomic control options
bool atomicIgnoreDenormalMode = false;
bool atomicRemoteMemory = false;
diff --git a/flang/lib/Frontend/CompilerInstance.cpp b/flang/lib/Frontend/CompilerInstance.cpp
index 02f39376f1d78..2416d3b593481 100644
--- a/flang/lib/Frontend/CompilerInstance.cpp
+++ b/flang/lib/Frontend/CompilerInstance.cpp
@@ -381,6 +381,7 @@ bool CompilerInstance::setUpTargetMachine() {
llvm::TargetOptions tOpts = llvm::TargetOptions();
tOpts.EnableAIXExtendedAltivecABI = targetOpts.EnableAIXExtendedAltivecABI;
+ tOpts.EnableMachineFunctionSplitter = targetOpts.SplitMachineFunctions;
tOpts.VecLib = convertDriverVectorLibraryToVectorLibrary(CGOpts.getVecLib());
tOpts.DisableIntegratedAS = CGOpts.DisableIntegratedAS;
tOpts.FunctionSections = CGOpts.FunctionSections;
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index b57bc4583be38..fef48a279ad72 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -610,6 +610,9 @@ static void parseTargetArgs(TargetOptions &opts, llvm::opt::ArgList &args) {
}
}
+ opts.SplitMachineFunctions =
+ args.hasArg(clang::options::OPT_fsplit_machine_functions);
+
opts.asmVerbose = args.hasFlag(clang::options::OPT_fverbose_asm,
clang::options::OPT_fno_verbose_asm, false);
}
diff --git a/flang/test/Driver/fsplit-machine-functions.f90 b/flang/test/Driver/fsplit-machine-functions.f90
new file mode 100644
index 0000000000000..2a0ffe61811fc
--- /dev/null
+++ b/flang/test/Driver/fsplit-machine-functions.f90
@@ -0,0 +1,14 @@
+! Test handling of -fsplit-machine-functions and -fno-split-machine-functions.
+
+! RUN: %if x86-registered-target %{ %flang -### --target=x86_64-unknown-linux-gnu %s 2>&1 | FileCheck %s --check-prefix=NO-SPLIT-MACHINE-FUNCTIONS %}
+! RUN: %if x86-registered-target %{ %flang -### --target=x86_64-unknown-linux-gnu -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefix=SPLIT-MACHINE-FUNCTIONS %}
+! RUN: %if x86-registered-target %{ %flang -### --target=x86_64-unknown-linux-gnu -fno-split-machine-functions %s 2>&1 | FileCheck %s --check-prefix=NO-SPLIT-MACHINE-FUNCTIONS %}
+! RUN: %if x86-registered-target %{ %flang -### --target=x86_64-unknown-linux-gnu -fsplit-machine-functions -fno-split-machine-functions %s 2>&1 | FileCheck %s --check-prefix=NO-SPLIT-MACHINE-FUNCTIONS %}
+! RUN: %if x86-registered-target %{ %flang -### --target=x86_64-unknown-linux-gnu -fno-split-machine-functions -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefix=SPLIT-MACHINE-FUNCTIONS %}
+! RUN: %if arm-registered-target %{ not %flang -### --target=arm-unknown-linux -fsplit-machine-functions %s 2>&1 | FileCheck %s --check-prefix=UNSUPPORTED-OPT %}
+! RUN: %if arm-registered-target %{ %flang -### --target=arm-unknown-linux -fno-split-machine-functions %s 2>&1 | FileCheck %s --check-prefix=NO-SPLIT-MACHINE-FUNCTIONS %}
+
+! SPLIT-MACHINE-FUNCTIONS: "-fsplit-machine-functions"
+! NO-SPLIT-MACHINE-FUNCTIONS-NOT: "-fsplit-machine-functions"
+! UNSUPPORTED-OPT: error: unsupported option '-fsplit-machine-functions' for target
+
diff --git a/flang/test/Driver/split-machine-function-pass.f90 b/flang/test/Driver/split-machine-function-pass.f90
new file mode 100644
index 0000000000000..cf8bd0eafb624
--- /dev/null
+++ b/flang/test/Driver/split-machine-function-pass.f90
@@ -0,0 +1,12 @@
+! Verify that the MachineFunctionSplitter pass is enabled while passing -fsplit-machine-functions.
+
+! REQUIRES: x86-registered-target
+
+! RUN: %flang_fc1 -S -fsplit-machine-functions %s -triple x86_64-unknown-linux-gnu -mllvm -debug-pass=Structure -o /dev/null 2>&1 | FileCheck %s --check-prefix=SPLIT
+! RUN: %flang_fc1 -S %s -triple x86_64-unknown-linux-gnu -mllvm -debug-pass=Structure -o /dev/null 2>&1 | FileCheck %s --check-prefix=NO-SPLIT
+
+! SPLIT: Machine Function Splitter Transformation
+! NO-SPLIT-NOT: Machine Function Splitter Transformation
+
+subroutine test
+end subroutine test
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