For building v8 using gn on aix_ppc64, linux_s390x and linux_ppc64.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 320b7fce75bb11af6037a317aecf98aaeb47c8f4..7ba33fd299c93abfedc3a2f2b2e5abf7906d28b2 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -162,6 +162,8 @@ config("compiler") {
     configs += [ "//build/config/nacl:compiler" ]
   } else if (is_ios || is_mac) {
     configs += [ "//build/config/mac:compiler" ]
+  } else if (current_os == "aix") {
+    configs += [ "//build/config/aix:compiler" ]
   }
 
   # See the definitions below.
@@ -175,13 +177,18 @@ config("compiler") {
   if (!is_win) {
     # Common GCC compiler flags setup.
     # --------------------------------
-    cflags += [ "-fno-strict-aliasing" ]  # See http://crbug.com/32204
-    cflags_cc += [
-      # Not exporting C++ inline functions can generally be applied anywhere
-      # so we do so here. Normal function visibility is controlled by
-      # //build/config/gcc:symbol_visibility_hidden.
-      "-fvisibility-inlines-hidden",
-    ]
+    if (current_os != "aix" &&

[Michael Achenbach, 2017/04/25 14:08:30]

Just double-checking: You don't need the aix check anymore?

[rayb, 2017/04/25 17:28:48]

We only support AIX on ppc64 BE. So further checking current_os != aix, seemed
redundant. Also I don't know the behavior for AIX running on other platforms,
but I do know AIX on ppc64 does not have support for these flags. 

+        !(is_linux && (current_cpu == "s390x" || current_cpu == "s390" ||
+                       current_cpu == "ppc64" || current_cpu == "ppc"))) {
+      cflags_cc += [

[Michael Achenbach, 2017/04/18 13:46:04]

This doesn't include -fno-strict-aliasing in cflags anymore. Also for the
non-aix/non-ppc/etc cases. If this is intended, I'd prefer to have it in a
separate CL and with separate description.

[rayb, 2017/04/25 00:41:04]

Acknowledged.

+        "fno-strict-aliasing",
+
+        # Not exporting C++ inline functions can generally be applied anywhere
+        # so we do so here. Normal function visibility is controlled by
+        # //build/config/gcc:symbol_visibility_hidden.
+        "-fvisibility-inlines-hidden",
+      ]
+    }
 
     # Stack protection.
     if (is_mac) {
@@ -200,14 +207,16 @@ config("compiler") {
       # The x86 toolchain currently has problems with stack-protector.
       if (is_android && current_cpu == "x86") {
         cflags += [ "-fno-stack-protector" ]
-      } else {
+      } else if (current_os != "aix") {
+        # Not available on aix.
         cflags += [ "-fstack-protector" ]
       }
     }
 
     # Linker warnings.
     if (fatal_linker_warnings && !(is_chromeos && current_cpu == "arm") &&
-        !(is_android && use_order_profiling) && !is_mac && !is_ios) {
+        !(is_android && use_order_profiling) && !is_mac && !is_ios &&
+        current_os != "aix") {
       # TODO(jochen): Enable this on chromeos on arm. http://crbug.com/356580
       # TODO(lizeb,pasko): Fix link errors when linking with order_profiling=1
       # crbug.com/485542
@@ -436,7 +445,7 @@ config("compiler") {
 
   # C++11 compiler flags setup.
   # ---------------------------
-  if (is_linux || is_android || (is_nacl && is_clang)) {
+  if (is_linux || is_android || (is_nacl && is_clang) || current_os == "aix") {
     # gnu++11 instead of c++11 is needed because some code uses typeof() (a
     # GNU extension).
     # TODO(thakis): Eventually switch this to c++11 instead,
@@ -1137,7 +1146,9 @@ config("chromium_code") {
     ]
 
     if (!is_debug && !using_sanitizer &&
-        (!is_linux || !is_clang || is_official_build)) {
+        (!is_linux || !is_clang || is_official_build) &&
+        (current_cpu != "s390x" && current_cpu != "s390" &&
+         current_cpu != "ppc64" && current_cpu != "ppc")) {

[Michael Achenbach, 2017/04/18 13:46:04]

nit: For readability, maybe we could add a helper variable somewhere for:
current_cpu != "s390x" && current_cpu != "s390" && current_cpu != "ppc64" &&
current_cpu != "ppc"

Or rather the inverse case, used in line 181. This or the inverse case are used
many times in multiple files. The four parts of the clause are always going
together and are hard to read if nested within other clauses.

[rayb, 2017/04/25 00:41:04]

Done.

       # _FORTIFY_SOURCE isn't really supported by Clang now, see
       # http://llvm.org/bugs/show_bug.cgi?id=16821.
       # It seems to work fine with Ubuntu 12 headers though, so use it in
@@ -1357,7 +1368,7 @@ if (is_win) {
       # Mac dead code stripping requires symbols.
       common_optimize_on_ldflags += [ "-Wl,-dead_strip" ]
     }
-  } else {
+  } else if (current_os != "aix") {
     # Non-Mac Posix flags.
 
     common_optimize_on_cflags += [
@@ -1371,12 +1382,14 @@ if (is_win) {
       "-ffunction-sections",
     ]
 
-    common_optimize_on_ldflags += [
-      # Specifically tell the linker to perform optimizations.
-      # See http://lwn.net/Articles/192624/ .
-      "-Wl,-O1",
-      "-Wl,--gc-sections",
-    ]
+    if (current_os != "aix") {

[Michael Achenbach, 2017/04/18 13:46:03]

This is already nested in a current_os != "aix" scope.

[rayb, 2017/04/25 00:41:04]

Done.

+      common_optimize_on_ldflags += [
+        # Specifically tell the linker to perform optimizations.
+        # See http://lwn.net/Articles/192624/ .
+        "-Wl,-O1",
+        "-Wl,--gc-sections",
+      ]
+    }
   }
 }