diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4473,6 +4473,7 @@
 defm caller_saves : BooleanFFlag<"caller-saves">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm reorder_blocks : BooleanFFlag<"reorder-blocks">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm branch_count_reg : BooleanFFlag<"branch-count-reg">, Group<clang_ignored_gcc_optimization_f_Group>;
+defm conserve_stack : BooleanFFlag<"conserve-stack">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm default_inline : BooleanFFlag<"default-inline">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm fat_lto_objects : BooleanFFlag<"fat-lto-objects">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm float_store : BooleanFFlag<"float-store">, Group<clang_ignored_gcc_optimization_f_Group>;
diff --git a/clang/test/Driver/clang_f_opts.c b/clang/test/Driver/clang_f_opts.c
--- a/clang/test/Driver/clang_f_opts.c
+++ b/clang/test/Driver/clang_f_opts.c
@@ -307,6 +307,7 @@
 // RUN:     -malign-functions=100                                             \
 // RUN:     -malign-loops=100                                                 \
 // RUN:     -malign-jumps=100                                                 \
+// RUN:     -fconserve-stack -fno-conserve-stack                              \
 // RUN:     %s 2>&1 | FileCheck --check-prefix=IGNORE %s
 // IGNORE-NOT: error: unknown argument
 
@@ -372,6 +373,8 @@
 // RUN: -fno-devirtualize-speculatively                                       \
 // RUN: -fslp-vectorize-aggressive                                            \
 // RUN: -fno-slp-vectorize-aggressive                                         \
+// RUN: -fconserve-stack                                                      \
+// RUN: -fno-conserve-stack                                                   \
 // RUN: %s 2>&1 | FileCheck --check-prefix=CHECK-WARNING %s
 // CHECK-WARNING-DAG: optimization flag '-finline-limit=1000' is not supported
 // CHECK-WARNING-DAG: optimization flag '-finline-limit' is not supported
@@ -432,6 +435,8 @@
 // CHECK-WARNING-DAG: optimization flag '-fno-devirtualize-speculatively' is not supported
 // CHECK-WARNING-DAG: the flag '-fslp-vectorize-aggressive' has been deprecated and will be ignored
 // CHECK-WARNING-DAG: the flag '-fno-slp-vectorize-aggressive' has been deprecated and will be ignored
+// CHECK-WARNING-DAG: optimization flag '-fconserve-stack' is not supported
+// CHECK-WARNING-DAG: optimization flag '-fno-conserve-stack' is not supported
 
 // Test that we mute the warning on these
 // RUN: %clang -### -finline-limit=1000 -Wno-invalid-command-line-argument              \