Use DWARF4 for mac and ios simulator builds, use DWARF3 for ios devic…

…e builds.

Removes some special-case code and potentially makes debug info a bit smaller.

Also stop passing -g2 to (non-pnacl) nacl compiles on mac, like already the case
on linux -- this helps with build determinism.

Bug: 942155,899438,906741,429358
Change-Id: Ic4c7138d232813e12426de2c161c78121bd3fc80
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1525041
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#640963}

build/config/compiler/BUILD.gn

@@ -172,8 +172,9 @@ if (gold_path == false) {
 }
 
 if (use_debug_fission == "default") {
-  use_debug_fission = is_debug && !is_android && !is_fuchsia && !is_win &&
-                      (use_gold || use_lld) && cc_wrapper == ""
+  use_debug_fission =
+      is_debug && !is_android && !is_fuchsia && !is_ios && !is_mac && !is_win &&
+      (use_gold || use_lld) && cc_wrapper == ""
 }
 
 # default_include_dirs ---------------------------------------------------------
@@ -2254,40 +2255,38 @@ config("symbols") {
       }
     }
   } else {
-    if (is_mac || is_ios) {
-      cflags = [ "-gdwarf-2" ]
-      if (is_mac && enable_dsyms) {
-        # If generating dSYMs, specify -fno-standalone-debug. This was
-        # originally specified for https://crbug.com/479841 because dsymutil
-        # could not handle a 4GB dSYM file. But dsymutil from Xcodes prior to
-        # version 7 also produces debug data that is incompatible with Breakpad
-        # dump_syms, so this is still required (https://crbug.com/622406).
-        cflags += [ "-fno-standalone-debug" ]
-      }
-    } else {
-      cflags = []
-      if (!use_debug_fission && current_cpu == "arm") {
-        # dump_syms has issues with dwarf4 on arm, https://crbug.com/744956
-        # TODO(thakis): Remove this again once dump_syms is fixed.
-        #
-        # debug fission needs DWARF DIEs to be emitted at version 4.
-        # Chrome OS emits Debug Frame in DWARF1 to make breakpad happy. [1]
-        # Unless Android needs debug fission, DWARF3 is the simplest solution.
-        #
-        # [1] crrev.com/a81d5ade0b043208e06ad71a38bcf9c348a1a52f
-        cflags += [ "-gdwarf-3" ]
-      }
+    if (is_mac && enable_dsyms) {
+      # If generating dSYMs, specify -fno-standalone-debug. This was
+      # originally specified for https://crbug.com/479841 because dsymutil
+      # could not handle a 4GB dSYM file. But dsymutil from Xcodes prior to
+      # version 7 also produces debug data that is incompatible with Breakpad
+      # dump_syms, so this is still required (https://crbug.com/622406).
+      cflags += [ "-fno-standalone-debug" ]
+    }
+    cflags = []
+    if (!use_debug_fission && current_cpu == "arm") {
+      # dump_syms has issues with dwarf4 on arm, https://crbug.com/744956
+      # TODO(thakis): Remove this again once dump_syms is fixed.
+      #
+      # debug fission needs DWARF DIEs to be emitted at version 4.
+      # Chrome OS emits Debug Frame in DWARF2's .debug_frame v1 to make breakpad
+      # happy [1].
+      # Unless Android needs debug fission, DWARF3 is the simplest solution.
+      #
+      # [1] crrev.com/a81d5ade0b043208e06ad71a38bcf9c348a1a52f
+      cflags += [ "-gdwarf-3" ]
+    }
 
-      # The gcc-based nacl compilers don't support -fdebug-compilation-dir (see
-      # elsewhere in this file), so they can't have build-dir-independent output.
-      # Disable symbols for nacl object files to get deterministic,
-      # build-directory-independent output. pnacl and nacl-clang do support that
-      # flag, so we can use use -g1 for pnacl and nacl-clang compiles.
-      # gcc nacl is is_nacl && !is_clang, pnacl and nacl-clang are && is_clang.
-      if (!is_nacl || is_clang) {
-        cflags += [ "-g2" ]
-      }
+    # The gcc-based nacl compilers don't support -fdebug-compilation-dir (see
+    # elsewhere in this file), so they can't have build-dir-independent output.
+    # Disable symbols for nacl object files to get deterministic,
+    # build-directory-independent output. pnacl and nacl-clang do support that
+    # flag, so we can use use -g1 for pnacl and nacl-clang compiles.
+    # gcc nacl is is_nacl && !is_clang, pnacl and nacl-clang are && is_clang.
+    if (!is_nacl || is_clang) {
+      cflags += [ "-g2" ]
     }
+
     if (use_debug_fission && !is_nacl && !is_android) {
       # NOTE: Some Chrome OS builds globally set |use_debug_fission| to true,
       # but they also build some targets against Android toolchains which aren't