[clang] [KeyInstr][Clang] Add Clang option -g[no-]key-instructions (PR #134627)
Orlando Cazalet-Hyams via cfe-commits
cfe-commits at lists.llvm.org
Wed May 14 09:58:29 PDT 2025
https://github.com/OCHyams updated https://github.com/llvm/llvm-project/pull/134627
>From 4d6e182ae2b6fea246492cd80c9fce75d1c7397d Mon Sep 17 00:00:00 2001
From: Orlando Cazalet-Hyams <orlando.hyams at sony.com>
Date: Mon, 31 Mar 2025 15:14:51 +0100
Subject: [PATCH 1/2] [KeyInstr][Clang] Add Clang option
-g[no-]key-instructions
This needs to be driver level to pass an -mllvm flag to LLVM.
Keep the flag help-hidden as the feature is under development.
---
This patch is part of a stack that teaches Clang to generate Key Instructions
metadata for C and C++.
The Key Instructions project is introduced, including a "quick summary" section
at the top which adds context for this PR, here:
https://discourse.llvm.org/t/rfc-improving-is-stmt-placement-for-better-interactive-debugging/82668
The feature is only functional in LLVM if LLVM is built with CMake flag
LLVM_EXPERIMENTAL_KEY_INSTRUCTIONs. Eventually that flag will be removed.
The Clang-side work is demoed here:
https://github.com/llvm/llvm-project/pull/130943
---
clang/include/clang/Basic/DebugOptions.def | 3 +++
clang/include/clang/Driver/Options.td | 6 ++++++
clang/lib/Driver/ToolChains/Clang.cpp | 7 +++++++
clang/test/CMakeLists.txt | 1 +
clang/test/KeyInstructions/flag.cpp | 15 +++++++++++++++
clang/test/KeyInstructions/lit.local.cfg | 2 ++
clang/test/lit.site.cfg.py.in | 1 +
7 files changed, 35 insertions(+)
create mode 100644 clang/test/KeyInstructions/flag.cpp
create mode 100644 clang/test/KeyInstructions/lit.local.cfg
diff --git a/clang/include/clang/Basic/DebugOptions.def b/clang/include/clang/Basic/DebugOptions.def
index bc96d5dfdf890..7a9d2e838c1ca 100644
--- a/clang/include/clang/Basic/DebugOptions.def
+++ b/clang/include/clang/Basic/DebugOptions.def
@@ -75,6 +75,9 @@ DEBUGOPT(DebugOmitUnreferencedMethods, 1, 0) ///< Omit unreferenced member
BENIGN_ENUM_DEBUGOPT(AssignmentTrackingMode, AssignmentTrackingOpts, 2,
AssignmentTrackingOpts::Disabled)
+/// Whether or not to use Key Instructions to determine breakpoint locations.
+BENIGN_DEBUGOPT(DebugKeyInstructions, 1, 0)
+
DEBUGOPT(DebugColumnInfo, 1, 0) ///< Whether or not to use column information
///< in debug info.
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index bd8df8f6a749a..9a4253113488d 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4664,6 +4664,12 @@ def gembed_source : Flag<["-"], "gembed-source">, Group<g_flags_Group>,
def gno_embed_source : Flag<["-"], "gno-embed-source">, Group<g_flags_Group>,
Flags<[NoXarchOption]>,
HelpText<"Restore the default behavior of not embedding source text in DWARF debug sections">;
+defm key_instructions : BoolGOption<"key-instructions",
+ CodeGenOpts<"DebugKeyInstructions">, DefaultFalse,
+ NegFlag<SetFalse>, PosFlag<SetTrue, [], [],
+ "Enable Key Instructions, which reduces the jumpiness of optimized code stepping (DWARF only)."
+ " Requires LLVM built with LLVM_EXPERIMENTAL_KEY_INSTRUCTIONS.">,
+ BothFlags<[HelpHidden], [ClangOption, CLOption, CC1Option]>>;
def headerpad__max__install__names : Joined<["-"], "headerpad_max_install_names">;
def help : Flag<["-", "--"], "help">,
Visibility<[ClangOption, CC1Option, CC1AsOption,
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index a08bdba99bfe0..4b79eef83196e 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4776,6 +4776,13 @@ renderDebugOptions(const ToolChain &TC, const Driver &D, const llvm::Triple &T,
CmdArgs.push_back("-gembed-source");
}
+ if (Args.hasFlag(options::OPT_gkey_instructions,
+ options::OPT_gno_key_instructions, false)) {
+ CmdArgs.push_back("-gkey-instructions");
+ CmdArgs.push_back("-mllvm");
+ CmdArgs.push_back("-dwarf-use-key-instructions");
+ }
+
if (EmitCodeView) {
CmdArgs.push_back("-gcodeview");
diff --git a/clang/test/CMakeLists.txt b/clang/test/CMakeLists.txt
index 0d11fd2c07eb5..35a8042ac0e0a 100644
--- a/clang/test/CMakeLists.txt
+++ b/clang/test/CMakeLists.txt
@@ -26,6 +26,7 @@ llvm_canonicalize_cmake_booleans(
PPC_LINUX_DEFAULT_IEEELONGDOUBLE
LLVM_TOOL_LLVM_DRIVER_BUILD
LLVM_INCLUDE_SPIRV_TOOLS_TESTS
+ LLVM_EXPERIMENTAL_KEY_INSTRUCTIONS
)
configure_lit_site_cfg(
diff --git a/clang/test/KeyInstructions/flag.cpp b/clang/test/KeyInstructions/flag.cpp
new file mode 100644
index 0000000000000..93503dd4bdb4c
--- /dev/null
+++ b/clang/test/KeyInstructions/flag.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang -### -target x86_64 -c -gdwarf -gkey-instructions %s 2>&1 | FileCheck %s --check-prefixes=KEY-INSTRUCTIONS
+// RUN: %clang -### -target x86_64 -c -gdwarf -gno-key-instructions %s 2>&1 | FileCheck %s --check-prefixes=NO-KEY-INSTRUCTIONS
+//// Default: Off.
+// RUN: %clang -### -target x86_64 -c -gdwarf %s 2>&1 | FileCheck %s --check-prefixes=NO-KEY-INSTRUCTIONS
+
+//// Help hidden.
+// RUN %clang --help | FileCheck %s --check-prefix=HELP
+// HELP-NOT: key-instructions
+
+// KEY-INSTRUCTIONS: "-gkey-instructions"
+// KEY-INSTRUCTIONS: "-mllvm" "-dwarf-use-key-instructions"
+
+// NO-KEY-INSTRUCTIONS-NOT: key-instructions
+
+//// TODO: Add smoke test once some functionality has been added.
diff --git a/clang/test/KeyInstructions/lit.local.cfg b/clang/test/KeyInstructions/lit.local.cfg
new file mode 100644
index 0000000000000..482bd5c8ac251
--- /dev/null
+++ b/clang/test/KeyInstructions/lit.local.cfg
@@ -0,0 +1,2 @@
+if not config.has_key_instructions:
+ config.unsupported = True
diff --git a/clang/test/lit.site.cfg.py.in b/clang/test/lit.site.cfg.py.in
index e73acfc79d9ad..77c5f27f47c92 100644
--- a/clang/test/lit.site.cfg.py.in
+++ b/clang/test/lit.site.cfg.py.in
@@ -48,6 +48,7 @@ config.ppc_linux_default_ieeelongdouble = @PPC_LINUX_DEFAULT_IEEELONGDOUBLE@
config.have_llvm_driver = @LLVM_TOOL_LLVM_DRIVER_BUILD@
config.spirv_tools_tests = @LLVM_INCLUDE_SPIRV_TOOLS_TESTS@
config.substitutions.append(("%llvm-version-major", "@LLVM_VERSION_MAJOR@"))
+config.has_key_instructions = @LLVM_EXPERIMENTAL_KEY_INSTRUCTIONS@
import lit.llvm
lit.llvm.initialize(lit_config, config)
>From 5c9d5e03fe0c3ff495aca673279b3e479836b9ad Mon Sep 17 00:00:00 2001
From: Orlando Cazalet-Hyams <orlando.hyams at sony.com>
Date: Wed, 14 May 2025 17:57:43 +0100
Subject: [PATCH 2/2] Move clang/test/KeyInstructions ->
clang/test/DebugInfo/KeyInstructions
---
clang/test/{ => DebugInfo}/KeyInstructions/flag.cpp | 0
clang/test/{ => DebugInfo}/KeyInstructions/lit.local.cfg | 0
2 files changed, 0 insertions(+), 0 deletions(-)
rename clang/test/{ => DebugInfo}/KeyInstructions/flag.cpp (100%)
rename clang/test/{ => DebugInfo}/KeyInstructions/lit.local.cfg (100%)
diff --git a/clang/test/KeyInstructions/flag.cpp b/clang/test/DebugInfo/KeyInstructions/flag.cpp
similarity index 100%
rename from clang/test/KeyInstructions/flag.cpp
rename to clang/test/DebugInfo/KeyInstructions/flag.cpp
diff --git a/clang/test/KeyInstructions/lit.local.cfg b/clang/test/DebugInfo/KeyInstructions/lit.local.cfg
similarity index 100%
rename from clang/test/KeyInstructions/lit.local.cfg
rename to clang/test/DebugInfo/KeyInstructions/lit.local.cfg
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