[Linux] Enable frame pointers when building Swift libraries.

Turn on frame pointers for the Swift runtime libraries.  This makes
backtraces that go through the runtimes more reliable without having
to parse DWARF data.

rdar://116112040

stdlib/cmake/modules/AddSwiftStdlib.cmake

@@ -134,6 +134,11 @@ function(_add_target_variant_c_compile_link_flags)
                        "-fcoverage-mapping")
   endif()
 
+  # Use frame pointers on Linux
+  if("${CFLAGS_SDK}" STREQUAL "LINUX")
+    list(APPEND result "-fno-omit-frame-pointer")
+  endif()
+
   _compute_lto_flag("${CFLAGS_ENABLE_LTO}" _lto_flag_out)
   if (_lto_flag_out)
     list(APPEND result "${_lto_flag_out}")
@@ -310,6 +315,11 @@ function(_add_target_variant_c_compile_flags)
                        "-fcoverage-mapping")
   endif()
 
+  # Use frame pointers on Linux
+  if("${CFLAGS_SDK}" STREQUAL "LINUX")
+    list(APPEND result "-fno-omit-frame-pointer")
+  endif()
+
   if((CFLAGS_ARCH STREQUAL "armv7" OR CFLAGS_ARCH STREQUAL "aarch64") AND
      (CFLAGS_SDK STREQUAL "LINUX" OR CFLAGS_SDK STREQUAL "ANDROID"))
      list(APPEND result -funwind-tables)
@@ -943,6 +953,11 @@ function(add_swift_target_library_single target name)
     set(install_in_component "${SWIFTLIB_SINGLE_INSTALL_IN_COMPONENT}")
   endif()
 
+  # Use frame pointers on Linux
+  if ("${SWIFTLIB_SINGLE_SDK}" STREQUAL "LINUX")
+    list(APPEND SWIFTLIB_SINGLE_SWIFT_COMPILE_FLAGS "-Xcc" "-fno-omit-frame-pointer")
+  endif()
+
   # FIXME: don't actually depend on the libraries in SWIFTLIB_SINGLE_LINK_LIBRARIES,
   # just any swiftmodule files that are associated with them.
   handle_swift_sources(
@@ -2634,6 +2649,10 @@ function(_add_swift_target_executable_single name)
       -vfsoverlay;"${SWIFT_WINDOWS_VFS_OVERLAY}")
   endif()
 
+  if ("${SWIFTEXE_SINGLE_SDK}" STREQUAL "LINUX")
+    list(APPEND SWIFTEXE_SINGLE_COMPILE_FLAGS "-Xcc" "-fno-omit-frame-pointer")
+  endif()
+
   handle_swift_sources(
       dependency_target
       unused_module_dependency_target

test/Backtracing/FatalError.swift

@@ -0,0 +1,53 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift %s -parse-as-library -Onone -g -o %t/FatalError
+// RUN: %target-codesign %t/FatalError
+// RUN: (env SWIFT_BACKTRACE=enable=yes,cache=no %target-run %t/FatalError 2>&1 || true) | %FileCheck %s
+
+// UNSUPPORTED: use_os_stdlib
+// UNSUPPORTED: back_deployment_runtime
+// UNSUPPORTED: asan
+// REQUIRES: executable_test
+// REQUIRES: backtracing
+// REQUIRES: OS=macosx || OS=linux-gnu
+
+func level1() {
+  level2()
+}
+
+func level2() {
+  level3()
+}
+
+func level3() {
+  level4()
+}
+
+func level4() {
+  level5()
+}
+
+func level5() {
+  fatalError("Going to crash")
+}
+
+@main
+struct FatalError {
+  static func main() {
+    level1()
+  }
+}
+
+// CHECK: *** Program crashed: Illegal instruction at 0x{{[0-9a-f]+}} ***
+
+// CHECK: Thread 0 "FatalError" crashed:
+
+// CHECK:      0               0x{{[0-9a-f]+}} _assertionFailure(_:_:file:line:flags:) + {{[0-9]+}} in libswiftCore.so at {{.*}}/AssertCommon.swift:{{[0-9]+}}:{{[0-9]+}}
+// CHECK-NEXT: 1 [ra]          0x{{[0-9a-f]+}} level5() + {{[0-9]+}} in FatalError at {{.*}}/FatalError.swift:30:3
+// CHECK-NEXT: 2 [ra]          0x{{[0-9a-f]+}} level4() + {{[0-9]+}} in FatalError at {{.*}}/FatalError.swift:26:3
+// CHECK-NEXT: 3 [ra]          0x{{[0-9a-f]+}} level3() + {{[0-9]+}} in FatalError at {{.*}}/FatalError.swift:22:3
+// CHECK-NEXT: 4 [ra]          0x{{[0-9a-f]+}} level2() + {{[0-9]+}} in FatalError at {{.*}}/FatalError.swift:18:3
+// CHECK-NEXT: 5 [ra]          0x{{[0-9a-f]+}} level1() + {{[0-9]+}} in FatalError at {{.*}}/FatalError.swift:14:3
+// CHECK-NEXT: 6 [ra]          0x{{[0-9a-f]+}} static FatalError.main() + {{[0-9]+}} in FatalError at {{.*}}/FatalError.swift:36:5
+// CHECK-NEXT: 7 [ra] [system] 0x{{[0-9a-f]+}} static FatalError.$main() + {{[0-9]+}} in FatalError at {{.*}}/<compiler-generated>
+// CHECK-NEXT: 8 [ra] 0x{{[0-9a-f]+}} main + {{[0-9]+}} in FatalError at {{.*}}/FatalError.swift
+