[clang][Driver] Support Outline Flags on RISC-V and X86 #163664
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These two targets both also support the machine outliner, so these flags should probably be cross-target. This updates the docs for these flags as well.
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This was referenced Oct 16, 2025
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@llvm/pr-subscribers-backend-risc-v @llvm/pr-subscribers-clang Author: Sam Elliott (lenary) ChangesThese two targets both also support the machine outliner, so these flags Full diff: https://github.com/llvm/llvm-project/pull/163664.diff 6 Files Affected:
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 611b68e5281f0..d62b771f463ea 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -5127,12 +5127,16 @@ def mms_bitfields : Flag<["-"], "mms-bitfields">, Group<m_Group>,
Visibility<[ClangOption, CC1Option]>,
HelpText<"Set the default structure layout to be compatible with the Microsoft compiler standard">,
MarshallingInfoFlag<LangOpts<"MSBitfields">>;
-def moutline : Flag<["-"], "moutline">, Group<f_clang_Group>,
- Visibility<[ClangOption, CC1Option]>,
- HelpText<"Enable function outlining (AArch64 only)">;
-def mno_outline : Flag<["-"], "mno-outline">, Group<f_clang_Group>,
- Visibility<[ClangOption, CC1Option]>,
- HelpText<"Disable function outlining (AArch64 only)">;
+def moutline
+ : Flag<["-"], "moutline">,
+ Group<f_clang_Group>,
+ Visibility<[ClangOption, CC1Option]>,
+ HelpText<"Enable function outlining (AArch64,Arm,RISC-V,X86 only)">;
+def mno_outline
+ : Flag<["-"], "mno-outline">,
+ Group<f_clang_Group>,
+ Visibility<[ClangOption, CC1Option]>,
+ HelpText<"Disable function outlining (AArch64,Arm,RISC-V,X86 only)">;
def mno_ms_bitfields : Flag<["-"], "mno-ms-bitfields">, Group<m_Group>,
HelpText<"Do not set the default structure layout to be compatible with the Microsoft compiler standard">;
def mskip_rax_setup : Flag<["-"], "mskip-rax-setup">, Group<m_Group>,
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 99400ac701fbe..24b12fbf88f6f 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -2916,12 +2916,16 @@ void tools::addMachineOutlinerArgs(const Driver &D,
if (Arg *A = Args.getLastArg(options::OPT_moutline,
options::OPT_mno_outline)) {
if (A->getOption().matches(options::OPT_moutline)) {
- // We only support -moutline in AArch64 and ARM targets right now. If
- // we're not compiling for these, emit a warning and ignore the flag.
- // Otherwise, add the proper mllvm flags.
- if (!(Triple.isARM() || Triple.isThumb() || Triple.isAArch64())) {
+ // We only support -moutline in AArch64, ARM, RISC-V and X86 targets right
+ // now. If we're not compiling for these, emit a warning and ignore the
+ // flag. Otherwise, add the proper mllvm flags.
+ if (!(Triple.isARM() || Triple.isThumb() || Triple.isAArch64() ||
+ Triple.isRISCV() || Triple.isX86())) {
D.Diag(diag::warn_drv_moutline_unsupported_opt) << Triple.getArchName();
} else {
+ // FIXME: This should probably use the `nooutline` attribute rather than
+ // tweaking Pipeline Pass flags, so `-mno-outline` and `-moutline`
+ // objects can be combined correctly during LTO.
addArg(Twine("-enable-machine-outliner"));
}
} else {
diff --git a/clang/test/Driver/aarch64-outliner.c b/clang/test/Driver/aarch64-outliner.c
index c5d28d121513f..5ed822f122fc4 100644
--- a/clang/test/Driver/aarch64-outliner.c
+++ b/clang/test/Driver/aarch64-outliner.c
@@ -4,6 +4,3 @@
// RUN: %clang --target=aarch64 -moutline -mno-outline -S %s -### 2>&1 | FileCheck %s -check-prefix=OFF
// RUN: %clang --target=aarch64_be -moutline -mno-outline -S %s -### 2>&1 | FileCheck %s -check-prefix=OFF
// OFF: "-mllvm" "-enable-machine-outliner=never"
-// RUN: %clang --target=x86_64 -moutline -S %s -### 2>&1 | FileCheck %s -check-prefix=WARN
-// WARN: warning: 'x86_64' does not support '-moutline'; flag ignored [-Woption-ignored]
-// WARN-NOT: "-mllvm" "-enable-machine-outliner"
diff --git a/clang/test/Driver/riscv-outliner.c b/clang/test/Driver/riscv-outliner.c
new file mode 100644
index 0000000000000..9e9905ab4fd8a
--- /dev/null
+++ b/clang/test/Driver/riscv-outliner.c
@@ -0,0 +1,7 @@
+// RUN: %clang --target=riscv32 -moutline -S %s -### 2>&1 | FileCheck %s -check-prefix=ON
+// RUN: %clang --target=riscv64 -moutline -S %s -### 2>&1 | FileCheck %s -check-prefix=ON
+// ON: "-mllvm" "-enable-machine-outliner"
+
+// RUN: %clang --target=riscv32 -moutline -mno-outline -S %s -### 2>&1 | FileCheck %s -check-prefix=OFF
+// RUN: %clang --target=riscv64 -moutline -mno-outline -S %s -### 2>&1 | FileCheck %s -check-prefix=OFF
+// OFF: "-mllvm" "-enable-machine-outliner=never"
diff --git a/clang/test/Driver/unsupported-outliner.c b/clang/test/Driver/unsupported-outliner.c
new file mode 100644
index 0000000000000..ff543a8e36e2a
--- /dev/null
+++ b/clang/test/Driver/unsupported-outliner.c
@@ -0,0 +1,3 @@
+// RUN: %clang --target=ppc64 -moutline -S %s -### 2>&1 | FileCheck %s -check-prefix=WARN
+// WARN: warning: 'ppc64' does not support '-moutline'; flag ignored [-Woption-ignored]
+// WARN-NOT: "-mllvm" "-enable-machine-outliner"
diff --git a/clang/test/Driver/x86-outliner.c b/clang/test/Driver/x86-outliner.c
new file mode 100644
index 0000000000000..e2af85d3d16ab
--- /dev/null
+++ b/clang/test/Driver/x86-outliner.c
@@ -0,0 +1,7 @@
+// RUN: %clang --target=i386 -moutline -S %s -### 2>&1 | FileCheck %s -check-prefix=ON
+// RUN: %clang --target=x86_64 -moutline -S %s -### 2>&1 | FileCheck %s -check-prefix=ON
+// ON: "-mllvm" "-enable-machine-outliner"
+
+// RUN: %clang --target=i386 -moutline -mno-outline -S %s -### 2>&1 | FileCheck %s -check-prefix=OFF
+// RUN: %clang --target=x86_64 -moutline -mno-outline -S %s -### 2>&1 | FileCheck %s -check-prefix=OFF
+// OFF: "-mllvm" "-enable-machine-outliner=never"
|
topperc
reviewed
Oct 16, 2025
| // We only support -moutline in AArch64, ARM, RISC-V and X86 targets right | ||
| // now. If we're not compiling for these, emit a warning and ignore the | ||
| // flag. Otherwise, add the proper mllvm flags. | ||
| if (!(Triple.isARM() || Triple.isThumb() || Triple.isAArch64() || |
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Should we swap the if and else body to get rid of this !?
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These two targets both also support the machine outliner, so these flags
should probably be cross-target. This updates the docs for these flags
as well.