https://github.com/SLTozer updated
https://github.com/llvm/llvm-project/pull/110000
>From 6a873f5c487a936344f6cd226b7d525b406f34b2 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.to...@sony.com>
Date: Wed, 25 Sep 2024 15:08:39 +0100
Subject: [PATCH 1/9] [Clang] Add "extend lifetime" flags and release note
Following the commit that added the fake use intrinsic to LLVM, this patch
adds a pair of flags for the clang frontend that emit fake use intrinsics,
for the purpose of extending the lifetime of variables (either all source
variables, or just the `this` pointer). This patch does not implement the
fake use intrinsic emission of the flags themselves, it simply adds the flags,
the corresponding release note, and the attachment of the `has_fake_uses`
attribute to affected functions; the remaining functionality appears in the
next patch.
---
clang/docs/ReleaseNotes.rst | 10 ++++++++++
clang/include/clang/Basic/CodeGenOptions.def | 6 ++++++
clang/include/clang/Driver/Options.td | 9 +++++++++
clang/lib/CodeGen/CGCall.cpp | 4 ++++
clang/lib/Driver/ToolChains/Clang.cpp | 5 +++++
clang/lib/Frontend/CompilerInvocation.cpp | 5 +++++
clang/test/CodeGen/extend-lifetimes-hasfakeuses.c | 12 ++++++++++++
7 files changed, 51 insertions(+)
create mode 100644 clang/test/CodeGen/extend-lifetimes-hasfakeuses.c
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 601a233b81904f..f88fcef9bdade7 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -412,6 +412,16 @@ New Compiler Flags
only for thread-local variables, and none (which corresponds to the
existing ``-fno-c++-static-destructors`` flag) skips all static
destructors registration.
+- The ``-fextend-lifetimes`` and ``-fextend-this-ptr`` flags have been added to
+ allow for improved debugging of optimized code. Using ``-fextend-lifetimes``
+ will cause Clang to generate code that tries to preserve the lifetimes of
+ source variables, meaning that variables will typically be visible in a
+ debugger more often. The ``-fextend-this-ptr`` flag has the same behaviour,
+ but applies only to the ``this`` variable in C++ class member functions. Note
+ that this flag modifies the optimizations that Clang performs, which will
+ result in reduced performance in generated code; however, this feature will
+ not extend the lifetime of some variables in cases where doing so would have
+ too severe an impact on generated code performance.
Deprecated Compiler Flags
-------------------------
diff --git a/clang/include/clang/Basic/CodeGenOptions.def
b/clang/include/clang/Basic/CodeGenOptions.def
index 4cf22c4ee08ce0..2f155f7df49a3a 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -393,6 +393,12 @@ CODEGENOPT(EnableTLSDESC, 1, 0)
/// Bit size of immediate TLS offsets (0 == use the default).
VALUE_CODEGENOPT(TLSSize, 8, 0)
+/// Whether to extend the live range of the `this` pointer.
+CODEGENOPT(ExtendThisPtr, 1, 0)
+
+/// Whether to extend the live ranges of all local variables.
+CODEGENOPT(ExtendLifetimes, 1, 0)
+
/// The default stack protector guard offset to use.
VALUE_CODEGENOPT(StackProtectorGuardOffset, 32, INT_MAX)
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index 9c356c9d2ea4ef..b2e22c9cb6bd95 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4298,6 +4298,15 @@ def stack_usage_file : Separate<["-"],
"stack-usage-file">,
Visibility<[CC1Option]>,
HelpText<"Filename (or -) to write stack usage output to">,
MarshallingInfoString<CodeGenOpts<"StackUsageOutput">>;
+def fextend_this_ptr : Flag <["-"], "fextend-this-ptr">, Group<f_Group>,
+ MarshallingInfoFlag<CodeGenOpts<"ExtendThisPtr">>,
+ HelpText<"Extend the lifetime of the 'this' pointer to improve visibility "
+ "in optimized debugging">, Visibility<[ClangOption, CC1Option]>;
+def fextend_lifetimes : Flag <["-"], "fextend-lifetimes">, Group<f_Group>,
+ MarshallingInfoFlag<CodeGenOpts<"ExtendLifetimes">>,
+ HelpText<"Extend the lifetimes of local variables and parameters to improve "
+ "visibility in optimized debugging">,
+ Visibility<[ClangOption, CC1Option]>;
defm unique_basic_block_section_names :
BoolFOption<"unique-basic-block-section-names",
CodeGenOpts<"UniqueBasicBlockSectionNames">, DefaultFalse,
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 20455dbb820914..41195953c9a221 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2567,6 +2567,10 @@ void CodeGenModule::ConstructAttributeList(StringRef
Name,
if (shouldDisableTailCalls())
FuncAttrs.addAttribute("disable-tail-calls", "true");
+ // Mark the function as having fake uses when -fextend-lifetimes is on.
+ if (CodeGenOpts.ExtendLifetimes || CodeGenOpts.ExtendThisPtr)
+ FuncAttrs.addAttribute(llvm::Attribute::HasFakeUses);
+
// CPU/feature overrides. addDefaultFunctionDefinitionAttributes
// handles these separately to set them based on the global defaults.
GetCPUAndFeaturesAttributes(CalleeInfo.getCalleeDecl(), FuncAttrs);
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp
b/clang/lib/Driver/ToolChains/Clang.cpp
index 217c1a845f0a47..1068b0300b9c55 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7654,6 +7654,11 @@ void Clang::ConstructJob(Compilation &C, const JobAction
&JA,
if (Args.hasArg(options::OPT_fretain_comments_from_system_headers))
CmdArgs.push_back("-fretain-comments-from-system-headers");
+ if (Args.hasArg(options::OPT_fextend_this_ptr))
+ CmdArgs.push_back("-fextend-this-ptr");
+ if (Args.hasArg(options::OPT_fextend_lifetimes))
+ CmdArgs.push_back("-fextend-lifetimes");
+
// Forward -fcomment-block-commands to -cc1.
Args.AddAllArgs(CmdArgs, options::OPT_fcomment_block_commands);
// Forward -fparse-all-comments to -cc1.
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp
b/clang/lib/Frontend/CompilerInvocation.cpp
index 3dd94c31b2bc7a..a3e609ff1ffc3e 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -2245,6 +2245,11 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions
&Opts, ArgList &Args,
Args.getAllArgValues(OPT_fsanitize_trap_EQ), Diags,
Opts.SanitizeTrap);
+ Opts.ExtendThisPtr =
+ Opts.OptimizationLevel > 0 && Args.hasArg(OPT_fextend_this_ptr);
+ Opts.ExtendLifetimes =
+ Opts.OptimizationLevel > 0 && Args.hasArg(OPT_fextend_lifetimes);
+
Opts.EmitVersionIdentMetadata = Args.hasFlag(OPT_Qy, OPT_Qn, true);
if (!LangOpts->CUDAIsDevice)
diff --git a/clang/test/CodeGen/extend-lifetimes-hasfakeuses.c
b/clang/test/CodeGen/extend-lifetimes-hasfakeuses.c
new file mode 100644
index 00000000000000..081bace3dc7cce
--- /dev/null
+++ b/clang/test/CodeGen/extend-lifetimes-hasfakeuses.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 %s -emit-llvm -O2 -fextend-lifetimes -o - | FileCheck
--check-prefixes=CHECK-ALL,CHECK-O2 %s
+// RUN: %clang_cc1 %s -emit-llvm -O0 -fextend-lifetimes -o - | FileCheck
--check-prefixes=CHECK-ALL,CHECK-O0 %s
+
+// Checks that we emit the function attribute has_fake_uses when
+// -fextend-lifetimes is on and optimizations are enabled, and that it does not
+// when optimizations are disabled.
+
+// CHECK-ALL: define {{.*}}void @foo
+// CHECK-O2: attributes #0 = {{{.*}}has_fake_uses
+// CHECK-O0-NOT: attributes #0 = {{{.*}}has_fake_uses
+
+void foo() {}
>From 957a46887580334a0128bfabbfca6b98e5fb433a Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.to...@sony.com>
Date: Thu, 14 Nov 2024 11:35:45 +0000
Subject: [PATCH 2/9] Make options into BoolF types, remove added attribute
---
clang/docs/ReleaseNotes.rst | 11 +++++-----
clang/include/clang/Driver/Options.td | 21 +++++++++++--------
clang/lib/CodeGen/CGCall.cpp | 4 ----
clang/lib/Driver/ToolChains/Clang.cpp | 8 +++----
clang/lib/Frontend/CompilerInvocation.cpp | 5 -----
.../CodeGen/extend-lifetimes-hasfakeuses.c | 12 -----------
6 files changed, 22 insertions(+), 39 deletions(-)
delete mode 100644 clang/test/CodeGen/extend-lifetimes-hasfakeuses.c
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f88fcef9bdade7..78696bfd9b2c82 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -417,11 +417,12 @@ New Compiler Flags
will cause Clang to generate code that tries to preserve the lifetimes of
source variables, meaning that variables will typically be visible in a
debugger more often. The ``-fextend-this-ptr`` flag has the same behaviour,
- but applies only to the ``this`` variable in C++ class member functions. Note
- that this flag modifies the optimizations that Clang performs, which will
- result in reduced performance in generated code; however, this feature will
- not extend the lifetime of some variables in cases where doing so would have
- too severe an impact on generated code performance.
+ but applies only to the ``this`` variable in C++ class member functions,
+ meaning its effect is a strict subset of ``-fextend-lifetimes``. Note that
+ this flag modifies the optimizations that Clang performs, which will result
+ in reduced performance in generated code; however, this feature will not
+ extend the lifetime of some variables in cases where doing so would have too
+ severe of an impact on generated code performance.
Deprecated Compiler Flags
-------------------------
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index b2e22c9cb6bd95..76ec03a01e8f28 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4298,15 +4298,18 @@ def stack_usage_file : Separate<["-"],
"stack-usage-file">,
Visibility<[CC1Option]>,
HelpText<"Filename (or -) to write stack usage output to">,
MarshallingInfoString<CodeGenOpts<"StackUsageOutput">>;
-def fextend_this_ptr : Flag <["-"], "fextend-this-ptr">, Group<f_Group>,
- MarshallingInfoFlag<CodeGenOpts<"ExtendThisPtr">>,
- HelpText<"Extend the lifetime of the 'this' pointer to improve visibility "
- "in optimized debugging">, Visibility<[ClangOption, CC1Option]>;
-def fextend_lifetimes : Flag <["-"], "fextend-lifetimes">, Group<f_Group>,
- MarshallingInfoFlag<CodeGenOpts<"ExtendLifetimes">>,
- HelpText<"Extend the lifetimes of local variables and parameters to improve "
- "visibility in optimized debugging">,
- Visibility<[ClangOption, CC1Option]>;
+defm extend_this_ptr : BoolFOption<"extend-this-ptr",
+ CodeGenOpts<"ExtendThisPtr">, DefaultFalse,
+ PosFlag<SetTrue, [], [ClangOption, CC1Option],
+ "Extend the lifetime of the 'this' pointer to improve visibility "
+ "in optimized debugging">,
+ NegFlag<SetFalse>>;
+defm extend_lifetimes : BoolFOption<"extend-lifetimes",
+ CodeGenOpts<"ExtendLifetimes">, DefaultFalse,
+ PosFlag<SetTrue, [], [ClangOption, CC1Option],
+ "Extend the lifetimes of local variables and parameters to improve "
+ "visibility in optimized debugging">,
+ NegFlag<SetFalse>>;
defm unique_basic_block_section_names :
BoolFOption<"unique-basic-block-section-names",
CodeGenOpts<"UniqueBasicBlockSectionNames">, DefaultFalse,
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 41195953c9a221..20455dbb820914 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2567,10 +2567,6 @@ void CodeGenModule::ConstructAttributeList(StringRef
Name,
if (shouldDisableTailCalls())
FuncAttrs.addAttribute("disable-tail-calls", "true");
- // Mark the function as having fake uses when -fextend-lifetimes is on.
- if (CodeGenOpts.ExtendLifetimes || CodeGenOpts.ExtendThisPtr)
- FuncAttrs.addAttribute(llvm::Attribute::HasFakeUses);
-
// CPU/feature overrides. addDefaultFunctionDefinitionAttributes
// handles these separately to set them based on the global defaults.
GetCPUAndFeaturesAttributes(CalleeInfo.getCalleeDecl(), FuncAttrs);
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp
b/clang/lib/Driver/ToolChains/Clang.cpp
index 1068b0300b9c55..5a9a57eed0ba0e 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7654,10 +7654,10 @@ void Clang::ConstructJob(Compilation &C, const
JobAction &JA,
if (Args.hasArg(options::OPT_fretain_comments_from_system_headers))
CmdArgs.push_back("-fretain-comments-from-system-headers");
- if (Args.hasArg(options::OPT_fextend_this_ptr))
- CmdArgs.push_back("-fextend-this-ptr");
- if (Args.hasArg(options::OPT_fextend_lifetimes))
- CmdArgs.push_back("-fextend-lifetimes");
+ Args.addOptInFlag(CmdArgs, options::OPT_fextend_this_ptr,
+ options::OPT_fno_extend_this_ptr);
+ Args.addOptInFlag(CmdArgs, options::OPT_fextend_lifetimes,
+ options::OPT_fno_extend_lifetimes);
// Forward -fcomment-block-commands to -cc1.
Args.AddAllArgs(CmdArgs, options::OPT_fcomment_block_commands);
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp
b/clang/lib/Frontend/CompilerInvocation.cpp
index a3e609ff1ffc3e..3dd94c31b2bc7a 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -2245,11 +2245,6 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions
&Opts, ArgList &Args,
Args.getAllArgValues(OPT_fsanitize_trap_EQ), Diags,
Opts.SanitizeTrap);
- Opts.ExtendThisPtr =
- Opts.OptimizationLevel > 0 && Args.hasArg(OPT_fextend_this_ptr);
- Opts.ExtendLifetimes =
- Opts.OptimizationLevel > 0 && Args.hasArg(OPT_fextend_lifetimes);
-
Opts.EmitVersionIdentMetadata = Args.hasFlag(OPT_Qy, OPT_Qn, true);
if (!LangOpts->CUDAIsDevice)
diff --git a/clang/test/CodeGen/extend-lifetimes-hasfakeuses.c
b/clang/test/CodeGen/extend-lifetimes-hasfakeuses.c
deleted file mode 100644
index 081bace3dc7cce..00000000000000
--- a/clang/test/CodeGen/extend-lifetimes-hasfakeuses.c
+++ /dev/null
@@ -1,12 +0,0 @@
-// RUN: %clang_cc1 %s -emit-llvm -O2 -fextend-lifetimes -o - | FileCheck
--check-prefixes=CHECK-ALL,CHECK-O2 %s
-// RUN: %clang_cc1 %s -emit-llvm -O0 -fextend-lifetimes -o - | FileCheck
--check-prefixes=CHECK-ALL,CHECK-O0 %s
-
-// Checks that we emit the function attribute has_fake_uses when
-// -fextend-lifetimes is on and optimizations are enabled, and that it does not
-// when optimizations are disabled.
-
-// CHECK-ALL: define {{.*}}void @foo
-// CHECK-O2: attributes #0 = {{{.*}}has_fake_uses
-// CHECK-O0-NOT: attributes #0 = {{{.*}}has_fake_uses
-
-void foo() {}
>From 0901017098d5f6d8161d609dbe6846ae746a7ff4 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.to...@sony.com>
Date: Wed, 27 Nov 2024 18:14:54 +0000
Subject: [PATCH 3/9] Make extend lifetimes an = option
---
clang/include/clang/Basic/CodeGenOptions.def | 7 ++---
clang/include/clang/Basic/CodeGenOptions.h | 6 +++++
clang/include/clang/Driver/Options.td | 28 +++++++++++---------
clang/lib/Driver/ToolChains/Clang.cpp | 5 +---
4 files changed, 25 insertions(+), 21 deletions(-)
diff --git a/clang/include/clang/Basic/CodeGenOptions.def
b/clang/include/clang/Basic/CodeGenOptions.def
index 2f155f7df49a3a..2e6a99949647a5 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -393,11 +393,8 @@ CODEGENOPT(EnableTLSDESC, 1, 0)
/// Bit size of immediate TLS offsets (0 == use the default).
VALUE_CODEGENOPT(TLSSize, 8, 0)
-/// Whether to extend the live range of the `this` pointer.
-CODEGENOPT(ExtendThisPtr, 1, 0)
-
-/// Whether to extend the live ranges of all local variables.
-CODEGENOPT(ExtendLifetimes, 1, 0)
+/// The types of variables that we will extend the live ranges of.
+ENUM_CODEGENOPT(ExtendLifetimes, ExtendLifetimesKind, 2,
ExtendLifetimesKind::None)
/// The default stack protector guard offset to use.
VALUE_CODEGENOPT(StackProtectorGuardOffset, 32, INT_MAX)
diff --git a/clang/include/clang/Basic/CodeGenOptions.h
b/clang/include/clang/Basic/CodeGenOptions.h
index 2dcf98b465661e..7c4f9f6c534a01 100644
--- a/clang/include/clang/Basic/CodeGenOptions.h
+++ b/clang/include/clang/Basic/CodeGenOptions.h
@@ -95,6 +95,12 @@ class CodeGenOptions : public CodeGenOptionsBase {
Embed_Marker // Embed a marker as a placeholder for bitcode.
};
+ enum class ExtendLifetimesKind {
+ None,
+ This,
+ All,
+ };
+
enum InlineAsmDialectKind {
IAD_ATT,
IAD_Intel,
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index 76ec03a01e8f28..b5be9d891b1514 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4298,18 +4298,22 @@ def stack_usage_file : Separate<["-"],
"stack-usage-file">,
Visibility<[CC1Option]>,
HelpText<"Filename (or -) to write stack usage output to">,
MarshallingInfoString<CodeGenOpts<"StackUsageOutput">>;
-defm extend_this_ptr : BoolFOption<"extend-this-ptr",
- CodeGenOpts<"ExtendThisPtr">, DefaultFalse,
- PosFlag<SetTrue, [], [ClangOption, CC1Option],
- "Extend the lifetime of the 'this' pointer to improve visibility "
- "in optimized debugging">,
- NegFlag<SetFalse>>;
-defm extend_lifetimes : BoolFOption<"extend-lifetimes",
- CodeGenOpts<"ExtendLifetimes">, DefaultFalse,
- PosFlag<SetTrue, [], [ClangOption, CC1Option],
- "Extend the lifetimes of local variables and parameters to improve "
- "visibility in optimized debugging">,
- NegFlag<SetFalse>>;
+def fextend_lifetimes_EQ : Joined<["-"], "fextend-lifetimes=">, Group<f_Group>,
+ Visibility<[ClangOption, CC1Option]>,
+ HelpText<"Extend the lifetimes of variables to improve visibility in "
+ "optimized debugging">,
+ Values<"all,this,none">,
+ NormalizedValues<["All", "This", "None"]>,
+ NormalizedValuesScope<"CodeGenOptions::ExtendLifetimesKind">,
+ MarshallingInfoEnum<CodeGenOpts<"ExtendLifetimes">, "None">;
+def fextend_this_ptr : Flag<["-"], "fextend-this-ptr">,
+ Alias<fextend_lifetimes_EQ>, AliasArgs<["this"]>,
+ HelpText<"Extend the lifetime of the 'this' pointer to improve visibility "
+ "in optimized debugging">;
+def fextend_lifetimes : Flag<["-"], "fextend-lifetimes">,
+ Alias<fextend_lifetimes_EQ>, AliasArgs<["all"]>,
+ HelpText<"Extend the lifetimes of local variables and parameters to improve "
+ "visibility in optimized debugging">;
defm unique_basic_block_section_names :
BoolFOption<"unique-basic-block-section-names",
CodeGenOpts<"UniqueBasicBlockSectionNames">, DefaultFalse,
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp
b/clang/lib/Driver/ToolChains/Clang.cpp
index 5a9a57eed0ba0e..cedf64ba34e0d3 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7654,10 +7654,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction
&JA,
if (Args.hasArg(options::OPT_fretain_comments_from_system_headers))
CmdArgs.push_back("-fretain-comments-from-system-headers");
- Args.addOptInFlag(CmdArgs, options::OPT_fextend_this_ptr,
- options::OPT_fno_extend_this_ptr);
- Args.addOptInFlag(CmdArgs, options::OPT_fextend_lifetimes,
- options::OPT_fno_extend_lifetimes);
+ Args.AddLastArg(CmdArgs, options::OPT_fextend_lifetimes_EQ);
// Forward -fcomment-block-commands to -cc1.
Args.AddAllArgs(CmdArgs, options::OPT_fcomment_block_commands);
>From 984e0505c644244bb55474ea67c9b4c27fc3b0a4 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.to...@sony.com>
Date: Thu, 5 Dec 2024 11:06:15 +0000
Subject: [PATCH 4/9] Rename to -fextend-variable-liveness
---
clang/docs/ReleaseNotes.rst | 23 +++++++++-------
clang/include/clang/Basic/CodeGenOptions.def | 2 +-
clang/include/clang/Basic/CodeGenOptions.h | 2 +-
clang/include/clang/Driver/Options.td | 29 ++++++++++----------
clang/lib/Driver/ToolChains/Clang.cpp | 2 +-
5 files changed, 31 insertions(+), 27 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 78696bfd9b2c82..19a40d4666c727 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -412,17 +412,20 @@ New Compiler Flags
only for thread-local variables, and none (which corresponds to the
existing ``-fno-c++-static-destructors`` flag) skips all static
destructors registration.
-- The ``-fextend-lifetimes`` and ``-fextend-this-ptr`` flags have been added to
- allow for improved debugging of optimized code. Using ``-fextend-lifetimes``
- will cause Clang to generate code that tries to preserve the lifetimes of
- source variables, meaning that variables will typically be visible in a
- debugger more often. The ``-fextend-this-ptr`` flag has the same behaviour,
- but applies only to the ``this`` variable in C++ class member functions,
- meaning its effect is a strict subset of ``-fextend-lifetimes``. Note that
- this flag modifies the optimizations that Clang performs, which will result
+- The ``-fextend-variable-liveness`` flag has been added to allow for improved
+ debugging of optimized code. Using ``-fextend-variable-liveness`` will cause
+ Clang to generate code that tries to preserve the liveness of source
variables
+ through optimizations, meaning that variables will typically be visible in a
+ debugger more often. The flag has two levels: ``-fextend-variable-liveness``,
+ or ``-fextend-variable-liveness=all``, extendes the liveness of all user
+ variables and the ``this`` pointer. Alternatively ``-fextend-this-ptr``, or
+ ``-fextend-variable-liveness=this``, has the same behaviour but applies only
+ to the ``this`` variable in C++ class member functions, meaning its effect is
+ a strict subset of ``-fextend-variable-liveness``. Note that this flag
+ modifies the results of optimizations that Clang performs, which will result
in reduced performance in generated code; however, this feature will not
- extend the lifetime of some variables in cases where doing so would have too
- severe of an impact on generated code performance.
+ extend the liveness of some variables in cases where doing so would likely
+ have a severe impact on generated code performance.
Deprecated Compiler Flags
-------------------------
diff --git a/clang/include/clang/Basic/CodeGenOptions.def
b/clang/include/clang/Basic/CodeGenOptions.def
index 2e6a99949647a5..8d181c96bc9641 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -394,7 +394,7 @@ CODEGENOPT(EnableTLSDESC, 1, 0)
VALUE_CODEGENOPT(TLSSize, 8, 0)
/// The types of variables that we will extend the live ranges of.
-ENUM_CODEGENOPT(ExtendLifetimes, ExtendLifetimesKind, 2,
ExtendLifetimesKind::None)
+ENUM_CODEGENOPT(ExtendVariableLiveness, ExtendVariableLivenessKind, 2,
ExtendVariableLivenessKind::None)
/// The default stack protector guard offset to use.
VALUE_CODEGENOPT(StackProtectorGuardOffset, 32, INT_MAX)
diff --git a/clang/include/clang/Basic/CodeGenOptions.h
b/clang/include/clang/Basic/CodeGenOptions.h
index 7c4f9f6c534a01..f55d9513443e8c 100644
--- a/clang/include/clang/Basic/CodeGenOptions.h
+++ b/clang/include/clang/Basic/CodeGenOptions.h
@@ -95,7 +95,7 @@ class CodeGenOptions : public CodeGenOptionsBase {
Embed_Marker // Embed a marker as a placeholder for bitcode.
};
- enum class ExtendLifetimesKind {
+ enum class ExtendVariableLivenessKind {
None,
This,
All,
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index b5be9d891b1514..9ebf9f5a11f420 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4298,22 +4298,23 @@ def stack_usage_file : Separate<["-"],
"stack-usage-file">,
Visibility<[CC1Option]>,
HelpText<"Filename (or -) to write stack usage output to">,
MarshallingInfoString<CodeGenOpts<"StackUsageOutput">>;
-def fextend_lifetimes_EQ : Joined<["-"], "fextend-lifetimes=">, Group<f_Group>,
- Visibility<[ClangOption, CC1Option]>,
- HelpText<"Extend the lifetimes of variables to improve visibility in "
- "optimized debugging">,
+def fextend_variable_liveness_EQ : Joined<["-"], "fextend-variable-liveness=">,
+ Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
+ HelpText<"Extend the liveness of user variables through optimizations to "
+ "prevent stale or optimized-out variable values when debugging.">,
Values<"all,this,none">,
NormalizedValues<["All", "This", "None"]>,
- NormalizedValuesScope<"CodeGenOptions::ExtendLifetimesKind">,
- MarshallingInfoEnum<CodeGenOpts<"ExtendLifetimes">, "None">;
-def fextend_this_ptr : Flag<["-"], "fextend-this-ptr">,
- Alias<fextend_lifetimes_EQ>, AliasArgs<["this"]>,
- HelpText<"Extend the lifetime of the 'this' pointer to improve visibility "
- "in optimized debugging">;
-def fextend_lifetimes : Flag<["-"], "fextend-lifetimes">,
- Alias<fextend_lifetimes_EQ>, AliasArgs<["all"]>,
- HelpText<"Extend the lifetimes of local variables and parameters to improve "
- "visibility in optimized debugging">;
+ NormalizedValuesScope<"CodeGenOptions::ExtendVariableLivenessKind">,
+ MarshallingInfoEnum<CodeGenOpts<"ExtendVariableLiveness">, "None">;
+def fextend_this_ptr_liveness : Flag<["-"], "fextend-this-ptr-liveness">,
+ Alias<fextend_variable_liveness_EQ>, AliasArgs<["this"]>,
+ HelpText<"Extend the liveness of the `this` pointer through optimizations to
"
+ "prevent a stale or optimized-out value when debugging.">;
+def fextend_variable_liveness : Flag<["-"], "fextend-variable-liveness">,
+ Alias<fextend_variable_liveness_EQ>, AliasArgs<["all"]>,
+ HelpText<"Extend the liveness of all local variables and parameters through "
+ "optimizations to prevent stale or optimized-out variable values "
+ "when debugging.">;
defm unique_basic_block_section_names :
BoolFOption<"unique-basic-block-section-names",
CodeGenOpts<"UniqueBasicBlockSectionNames">, DefaultFalse,
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp
b/clang/lib/Driver/ToolChains/Clang.cpp
index cedf64ba34e0d3..ece14d1e3cbf7d 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7654,7 +7654,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction
&JA,
if (Args.hasArg(options::OPT_fretain_comments_from_system_headers))
CmdArgs.push_back("-fretain-comments-from-system-headers");
- Args.AddLastArg(CmdArgs, options::OPT_fextend_lifetimes_EQ);
+ Args.AddLastArg(CmdArgs, options::OPT_fextend_variable_liveness_EQ);
// Forward -fcomment-block-commands to -cc1.
Args.AddAllArgs(CmdArgs, options::OPT_fcomment_block_commands);
>From 8fdaaf7cd753dd38d9567a8246ba619ede946648 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.to...@sony.com>
Date: Thu, 5 Dec 2024 11:37:33 +0000
Subject: [PATCH 5/9] Add visibility to alias
---
clang/include/clang/Driver/Options.td | 2 ++
1 file changed, 2 insertions(+)
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index 9ebf9f5a11f420..d6e2c6e4732206 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4307,10 +4307,12 @@ def fextend_variable_liveness_EQ : Joined<["-"],
"fextend-variable-liveness=">,
NormalizedValuesScope<"CodeGenOptions::ExtendVariableLivenessKind">,
MarshallingInfoEnum<CodeGenOpts<"ExtendVariableLiveness">, "None">;
def fextend_this_ptr_liveness : Flag<["-"], "fextend-this-ptr-liveness">,
+ Visibility<[ClangOption, CC1Option]>,
Alias<fextend_variable_liveness_EQ>, AliasArgs<["this"]>,
HelpText<"Extend the liveness of the `this` pointer through optimizations to
"
"prevent a stale or optimized-out value when debugging.">;
def fextend_variable_liveness : Flag<["-"], "fextend-variable-liveness">,
+ Visibility<[ClangOption, CC1Option]>,
Alias<fextend_variable_liveness_EQ>, AliasArgs<["all"]>,
HelpText<"Extend the liveness of all local variables and parameters through "
"optimizations to prevent stale or optimized-out variable values "
>From 6835e13e8bf908e10ce9e6a485ad2d90367c9354 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.to...@sony.com>
Date: Thu, 12 Dec 2024 14:01:35 +0000
Subject: [PATCH 6/9] Add Driver test for flag
---
clang/test/Driver/extend-variable-liveness.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
create mode 100644 clang/test/Driver/extend-variable-liveness.c
diff --git a/clang/test/Driver/extend-variable-liveness.c
b/clang/test/Driver/extend-variable-liveness.c
new file mode 100644
index 00000000000000..bdd89d6f7721ce
--- /dev/null
+++ b/clang/test/Driver/extend-variable-liveness.c
@@ -0,0 +1,15 @@
+// Tests that -fextend-variable-liveness and its aliases are correctly passed
+// by the driver.
+
+// RUN: %clang -### -c %s 2>&1 | FileCheck %s --check-prefixes=CHECK,DEFAULT
+// RUN: %clang -fextend-variable-liveness=none -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,NONE
+// RUN: %clang -fextend-variable-liveness=this -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,THIS
+// RUN: %clang -fextend-this-ptr-liveness -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,THIS
+// RUN: %clang -fextend-variable-liveness=all -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,ALL
+// RUN: %clang -fextend-variable-liveness -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,ALL
+
+// CHECK: "-cc1"
+// DEFAULT-NOT: -fextend-variable-liveness
+// NONE-SAME: "-fextend-variable-liveness=none"
+// THIS-SAME: "-fextend-variable-liveness=this"
+// ALL-SAME: "-fextend-variable-liveness=all"
>From 7ff39f83e4d46721891f332244803cd40bd7a938 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.to...@sony.com>
Date: Thu, 12 Dec 2024 15:12:54 +0000
Subject: [PATCH 7/9] Improve help text for new flags
---
clang/include/clang/Driver/Options.td | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index d6e2c6e4732206..bd9e5407d3843b 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4301,7 +4301,11 @@ def stack_usage_file : Separate<["-"],
"stack-usage-file">,
def fextend_variable_liveness_EQ : Joined<["-"], "fextend-variable-liveness=">,
Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
HelpText<"Extend the liveness of user variables through optimizations to "
- "prevent stale or optimized-out variable values when debugging.">,
+ "prevent stale or optimized-out variable values when debugging. Can
"
+ "be applied to all user variables, or just to the C++ 'this' ptr. "
+ "May choose not to extend the liveness of some variables, such as "
+ "non-scalars larger than 4 unsigned ints, or variables in any "
+ "inlined functions.">,
Values<"all,this,none">,
NormalizedValues<["All", "This", "None"]>,
NormalizedValuesScope<"CodeGenOptions::ExtendVariableLivenessKind">,
@@ -4309,14 +4313,11 @@ def fextend_variable_liveness_EQ : Joined<["-"],
"fextend-variable-liveness=">,
def fextend_this_ptr_liveness : Flag<["-"], "fextend-this-ptr-liveness">,
Visibility<[ClangOption, CC1Option]>,
Alias<fextend_variable_liveness_EQ>, AliasArgs<["this"]>,
- HelpText<"Extend the liveness of the `this` pointer through optimizations to
"
- "prevent a stale or optimized-out value when debugging.">;
+ HelpText<"Alias for -fextend-variable-liveness=this.">;
def fextend_variable_liveness : Flag<["-"], "fextend-variable-liveness">,
Visibility<[ClangOption, CC1Option]>,
Alias<fextend_variable_liveness_EQ>, AliasArgs<["all"]>,
- HelpText<"Extend the liveness of all local variables and parameters through "
- "optimizations to prevent stale or optimized-out variable values "
- "when debugging.">;
+ HelpText<"Alias for -fextend-variable-liveness=all.">;
defm unique_basic_block_section_names :
BoolFOption<"unique-basic-block-section-names",
CodeGenOpts<"UniqueBasicBlockSectionNames">, DefaultFalse,
>From 5580215ee5227520ba31d7d51a4c947ccc47bfb8 Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.to...@sony.com>
Date: Thu, 9 Jan 2025 15:25:59 +0000
Subject: [PATCH 8/9] Remove -fextend-this-ptr alias
---
clang/docs/ReleaseNotes.rst | 16 ++++++++--------
clang/include/clang/Driver/Options.td | 4 ----
clang/test/Driver/extend-variable-liveness.c | 1 -
3 files changed, 8 insertions(+), 13 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 19a40d4666c727..1feaa835861292 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -418,14 +418,14 @@ New Compiler Flags
through optimizations, meaning that variables will typically be visible in a
debugger more often. The flag has two levels: ``-fextend-variable-liveness``,
or ``-fextend-variable-liveness=all``, extendes the liveness of all user
- variables and the ``this`` pointer. Alternatively ``-fextend-this-ptr``, or
- ``-fextend-variable-liveness=this``, has the same behaviour but applies only
- to the ``this`` variable in C++ class member functions, meaning its effect is
- a strict subset of ``-fextend-variable-liveness``. Note that this flag
- modifies the results of optimizations that Clang performs, which will result
- in reduced performance in generated code; however, this feature will not
- extend the liveness of some variables in cases where doing so would likely
- have a severe impact on generated code performance.
+ variables and the ``this`` pointer. Alternatively
+ ``-fextend-variable-liveness=this`` has the same behaviour but applies only
to
+ the ``this`` variable in C++ class member functions, meaning its effect is a
+ strict subset of ``-fextend-variable-liveness``. Note that this flag modifies
+ the results of optimizations that Clang performs, which will result in
reduced
+ performance in generated code; however, this feature will not extend the
+ liveness of some variables in cases where doing so would likely have a severe
+ impact on generated code performance.
Deprecated Compiler Flags
-------------------------
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index bd9e5407d3843b..b5b41ab3ea2a4a 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4310,10 +4310,6 @@ def fextend_variable_liveness_EQ : Joined<["-"],
"fextend-variable-liveness=">,
NormalizedValues<["All", "This", "None"]>,
NormalizedValuesScope<"CodeGenOptions::ExtendVariableLivenessKind">,
MarshallingInfoEnum<CodeGenOpts<"ExtendVariableLiveness">, "None">;
-def fextend_this_ptr_liveness : Flag<["-"], "fextend-this-ptr-liveness">,
- Visibility<[ClangOption, CC1Option]>,
- Alias<fextend_variable_liveness_EQ>, AliasArgs<["this"]>,
- HelpText<"Alias for -fextend-variable-liveness=this.">;
def fextend_variable_liveness : Flag<["-"], "fextend-variable-liveness">,
Visibility<[ClangOption, CC1Option]>,
Alias<fextend_variable_liveness_EQ>, AliasArgs<["all"]>,
diff --git a/clang/test/Driver/extend-variable-liveness.c
b/clang/test/Driver/extend-variable-liveness.c
index bdd89d6f7721ce..bbfb2ece6f297e 100644
--- a/clang/test/Driver/extend-variable-liveness.c
+++ b/clang/test/Driver/extend-variable-liveness.c
@@ -4,7 +4,6 @@
// RUN: %clang -### -c %s 2>&1 | FileCheck %s --check-prefixes=CHECK,DEFAULT
// RUN: %clang -fextend-variable-liveness=none -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,NONE
// RUN: %clang -fextend-variable-liveness=this -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,THIS
-// RUN: %clang -fextend-this-ptr-liveness -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,THIS
// RUN: %clang -fextend-variable-liveness=all -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,ALL
// RUN: %clang -fextend-variable-liveness -### -c %s 2>&1 | FileCheck %s
--check-prefixes=CHECK,ALL
>From 7a26d4e53fa1643af212def09247a32950101d6c Mon Sep 17 00:00:00 2001
From: Stephen Tozer <stephen.to...@sony.com>
Date: Fri, 24 Jan 2025 18:53:32 +0000
Subject: [PATCH 9/9] Shorten help text
---
clang/include/clang/Driver/Options.td | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/clang/include/clang/Driver/Options.td
b/clang/include/clang/Driver/Options.td
index b5b41ab3ea2a4a..1088f67e083e22 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4301,11 +4301,7 @@ def stack_usage_file : Separate<["-"],
"stack-usage-file">,
def fextend_variable_liveness_EQ : Joined<["-"], "fextend-variable-liveness=">,
Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
HelpText<"Extend the liveness of user variables through optimizations to "
- "prevent stale or optimized-out variable values when debugging. Can
"
- "be applied to all user variables, or just to the C++ 'this' ptr. "
- "May choose not to extend the liveness of some variables, such as "
- "non-scalars larger than 4 unsigned ints, or variables in any "
- "inlined functions.">,
+ "prevent stale or optimized-out variable values when debugging."
Values<"all,this,none">,
NormalizedValues<["All", "This", "None"]>,
NormalizedValuesScope<"CodeGenOptions::ExtendVariableLivenessKind">,
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