commit aef03c9b3bed5cef5a1940774b80128aefcb4095
Author: Kees Cook <keescook@chromium.org>
Date:   Fri May 6 12:47:43 2022 -0700

    [clang][auto-init] Deprecate -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
    
    GCC 12 has been released and contains unconditional support for
    -ftrivial-auto-var-init=zero:
    https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-ftrivial-auto-var-init
    
    Maintain compatibility with GCC, and remove the -enable flag for "zero"
    mode. The flag is left to generate an "unused" warning, though, to not
    break all the existing users. The flag will be fully removed in Clang 17.
    
    Link: https://github.com/llvm/llvm-project/issues/44842
    
    Reviewed By: nickdesaulniers, MaskRay, srhines, xbolva00
    
    Differential Revision: https://reviews.llvm.org/D125142

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c2fedad18e0c..2320f4a7a4fa 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -277,6 +277,10 @@ New Compiler Flags
 
 Deprecated Compiler Flags
 -------------------------
+- ``-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang``
+  has been deprecated. The flag will be removed in Clang 18.
+  ``-ftrivial-auto-var-init=zero`` is now available unconditionally, to be
+  compatible with GCC.
 
 Modified Compiler Flags
 -----------------------
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
index 56d8d508cdbc..282ecdbed4ce 100644
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -588,11 +588,6 @@ def warn_drv_darwin_sdk_invalid_settings : Warning<
   "SDK settings were ignored as 'SDKSettings.json' could not be parsed">,
   InGroup<DiagGroup<"darwin-sdk-settings">>;
 
-def err_drv_trivial_auto_var_init_zero_disabled : Error<
-  "'-ftrivial-auto-var-init=zero' hasn't been enabled; enable it at your own "
-  "peril for benchmarking purpose only with "
-  "'-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang'">;
-
 def err_drv_trivial_auto_var_init_stop_after_missing_dependency : Error<
   "'-ftrivial-auto-var-init-stop-after=*' is used without "
   "'-ftrivial-auto-var-init=zero' or '-ftrivial-auto-var-init=pattern'">;
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 4e85242f136b..f7744a109f9a 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -247,6 +247,12 @@ def : Flag<["-"], "fno-slp-vectorize-aggressive">, Group<clang_ignored_legacy_op
 def mmpx : Flag<["-"], "mmpx">, Group<clang_ignored_legacy_options_Group>;
 def mno_mpx : Flag<["-"], "mno-mpx">, Group<clang_ignored_legacy_options_Group>;
 
+// Retired with clang-16.0, to provide a deprecation period; it should
+// be removed in Clang 18 or later.
+def enable_trivial_var_init_zero : Flag<["-"], "enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang">,
+  Flags<[CC1Option, CoreOption, NoArgumentUnused]>,
+  Group<clang_ignored_legacy_options_Group>;
+
 // Group that ignores all gcc optimizations that won't be implemented
 def clang_ignored_gcc_optimization_f_Group : OptionGroup<
   "<clang_ignored_gcc_optimization_f_Group>">, Group<f_Group>, Flags<[Ignored]>;
@@ -2791,9 +2797,6 @@ def ftrivial_auto_var_init : Joined<["-"], "ftrivial-auto-var-init=">, Group<f_G
   NormalizedValuesScope<"LangOptions::TrivialAutoVarInitKind">,
   NormalizedValues<["Uninitialized", "Zero", "Pattern"]>,
   MarshallingInfoEnum<LangOpts<"TrivialAutoVarInit">, "Uninitialized">;
-def enable_trivial_var_init_zero : Flag<["-"], "enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang">,
-  Flags<[CC1Option, CoreOption, NoArgumentUnused]>,
-  HelpText<"Trivial automatic variable initialization to zero is only here for benchmarks, it'll eventually be removed, and I'm OK with that because I'm only using it to benchmark">;
 def ftrivial_auto_var_init_stop_after : Joined<["-"], "ftrivial-auto-var-init-stop-after=">, Group<f_Group>,
   Flags<[CC1Option, CoreOption]>, HelpText<"Stop initializing trivial automatic stack variables after the specified number of instances">,
   MarshallingInfoInt<LangOpts<"TrivialAutoVarInitStopAfter">>;
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index dd5596bc942e..e5fce3579359 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3458,8 +3458,6 @@ static void RenderTrivialAutoVarInitOptions(const Driver &D,
     }
 
   if (!TrivialAutoVarInit.empty()) {
-    if (TrivialAutoVarInit == "zero" && !Args.hasArg(options::OPT_enable_trivial_var_init_zero))
-      D.Diag(diag::err_drv_trivial_auto_var_init_zero_disabled);
     CmdArgs.push_back(
         Args.MakeArgString("-ftrivial-auto-var-init=" + TrivialAutoVarInit));
   }
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 45f93d6ba6ce..3d4a154af59f 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -719,7 +719,6 @@
 // RUN:     -fimplicit-modules \
 // RUN:     -fno-implicit-modules \
 // RUN:     -ftrivial-auto-var-init=zero \
-// RUN:     -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang \
 // RUN:     --version \
 // RUN:     -Werror /Zs -- %s 2>&1
 
diff --git a/clang/test/Driver/clang_f_opts.c b/clang/test/Driver/clang_f_opts.c
index 9c38b5906b7b..0ac67d60f7d3 100644
--- a/clang/test/Driver/clang_f_opts.c
+++ b/clang/test/Driver/clang_f_opts.c
@@ -569,18 +569,19 @@
 
 // RUN: %clang -### -S -ftrivial-auto-var-init=uninitialized %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-UNINIT %s
 // RUN: %clang -### -S -ftrivial-auto-var-init=pattern %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-PATTERN %s
-// RUN: %clang -### -S -ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-GOOD %s
-// RUN: %clang -### -S -ftrivial-auto-var-init=zero %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-BAD %s
+// RUN: %clang -### -S -ftrivial-auto-var-init=zero %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO %s
+// RUN: %clang -### -S -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang \
+// RUN:   -ftrivial-auto-var-init=zero %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-ENABLE-DEPRECATED %s
 // CHECK-TRIVIAL-UNINIT-NOT: hasn't been enabled
 // CHECK-TRIVIAL-PATTERN-NOT: hasn't been enabled
-// CHECK-TRIVIAL-ZERO-GOOD-NOT: hasn't been enabled
-// CHECK-TRIVIAL-ZERO-BAD: hasn't been enabled
+// CHECK-TRIVIAL-ZERO-NOT: hasn't been enabled
+// CHECK-TRIVIAL-ZERO-ENABLE-DEPRECATED: has been deprecated
 
 // RUN: %clang -### -S -ftrivial-auto-var-init=pattern -ftrivial-auto-var-init-stop-after=1 %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-PATTERN-STOP-AFTER %s
-// RUN: %clang -### -S -ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang -ftrivial-auto-var-init-stop-after=1 %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-STOP-AFTER %s
+// RUN: %clang -### -S -ftrivial-auto-var-init=zero -ftrivial-auto-var-init-stop-after=1 %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-STOP-AFTER %s
 // RUN: %clang -### -S -ftrivial-auto-var-init-stop-after=0 %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-STOP-AFTER-MISSING-DEPENDENCY %s
 // RUN: %clang -### -S -ftrivial-auto-var-init=pattern -ftrivial-auto-var-init-stop-after=0 %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-PATTERN-STOP-AFTER-INVALID-VALUE %s
-// RUN: %clang -### -S -ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang -ftrivial-auto-var-init-stop-after=0 %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-STOP-AFTER-INVALID-VALUE %s
+// RUN: %clang -### -S -ftrivial-auto-var-init=zero -ftrivial-auto-var-init-stop-after=0 %s 2>&1 | FileCheck -check-prefix=CHECK-TRIVIAL-ZERO-STOP-AFTER-INVALID-VALUE %s
 // CHECK-TRIVIAL-PATTERN-STOP-AFTER-NOT: is used without '-ftrivial-auto-var-init'
 // CHECK-TRIVIAL-PATTERN-STOP-AFTER-NOT: only accepts positive integers
 // CHECK-TRIVIAL-ZERO-STOP-AFTER-NOT: is used without '-ftrivial-auto-var-init'