Rename to -fextend-variable-liveness

Author: SLTozer

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
 -------------------------

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)

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,

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,

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);