GN: Factor CPU/ABI and code-generation options out of main :compiler config

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 29566e6d3f5e2fb8f87f16e0fc56ff1fe337bd19..29dc2d4eecd435725e295dd0554ad61d584636a7 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -131,6 +131,12 @@ config("compiler") {
     configs += [ "//build/config/mac:compiler" ]
   }
 
+  # See the definitions below.
+  configs += [
+    ":compiler_cpu_abi",
+    ":compiler_codegen",
+  ]
+
   # In general, Windows is totally different, but all the other builds share
   # some common GCC configuration.
   if (!is_win) {
@@ -213,124 +219,6 @@ config("compiler") {
       }
     }
 
-    # CPU architecture. We may or may not be doing a cross compile now, so for
-    # simplicity we always explicitly set the architecture.
-    if (current_cpu == "x64") {
-      cflags += [
-        "-m64",
-        "-march=x86-64",
-      ]
-      ldflags += [ "-m64" ]
-    } else if (current_cpu == "x86") {
-      cflags += [ "-m32" ]
-      ldflags += [ "-m32" ]
-      if (is_clang) {
-        cflags += [
-          # Else building libyuv gives clang's register allocator issues,
-          # see llvm.org/PR15798 / crbug.com/233709
-          "-momit-leaf-frame-pointer",
-
-          # Align the stack on 16-byte boundaries, http://crbug.com/418554.
-          "-mstack-alignment=16",
-          "-mstackrealign",
-        ]
-      }
-    } else if (current_cpu == "arm") {
-      if (is_clang && !is_android && !is_nacl) {
-        cflags += [
-          "-target",
-          "arm-linux-gnueabihf",
-        ]
-        ldflags += [
-          "-target",
-          "arm-linux-gnueabihf",
-        ]
-
-        # We need to disable clang's builtin assembler as it can't
-        # handle several asm files, crbug.com/124610
-        cflags += [ "-no-integrated-as" ]
-      }
-      if (!is_nacl) {
-        cflags += [
-          "-march=$arm_arch",
-          "-mfloat-abi=$arm_float_abi",
-        ]
-        if (arm_use_thumb) {
-          cflags += [ "-mthumb" ]
-          if (is_android && !is_clang) {
-            # Clang doesn't support this option.
-            cflags += [ "-mthumb-interwork" ]
-          }
-        }
-      }
-      if (arm_tune != "") {
-        cflags += [ "-mtune=$arm_tune" ]
-      }
-      if (!is_clang) {
-        # Clang doesn't support these flags.
-        cflags += [
-          # The tree-sra optimization (scalar replacement for
-          # aggregates enabling subsequent optimizations) leads to
-          # invalid code generation when using the Android NDK's
-          # compiler (r5-r7). This can be verified using
-          # webkit_unit_tests' WTF.Checked_int8_t test.
-          "-fno-tree-sra",
-
-          # The following option is disabled to improve binary
-          # size and performance in gcc 4.9.
-          "-fno-caller-saves",
-        ]
-      }
-    } else if (current_cpu == "mipsel") {
-      if (mips_arch_variant == "r6") {
-        cflags += [
-          "-mips32r6",
-          "-Wa,-mips32r6",
-        ]
-        if (is_android) {
-          ldflags += [
-            "-mips32r6",
-            "-Wl,-melf32ltsmip",
-          ]
-        }
-      } else if (mips_arch_variant == "r2") {
-        cflags += [
-          "-mips32r2",
-          "-Wa,-mips32r2",
-        ]
-        if (mips_float_abi == "hard" && mips_fpu_mode != "") {
-          cflags += [ "-m$mips_fpu_mode" ]
-        }
-      } else if (mips_arch_variant == "r1") {
-        cflags += [
-          "-mips32",
-          "-Wa,-mips32",
-        ]
-      }
-
-      if (mips_dsp_rev == 1) {
-        cflags += [ "-mdsp" ]
-      } else if (mips_dsp_rev == 2) {
-        cflags += [ "-mdspr2" ]
-      }
-
-      cflags += [ "-m${mips_float_abi}-float" ]
-    } else if (current_cpu == "mips64el") {
-      if (mips_arch_variant == "r6") {
-        cflags += [
-          "-mips64r6",
-          "-Wa,-mips64r6",
-        ]
-        ldflags += [ "-mips64r6" ]
-      } else if (mips_arch_variant == "r2") {
-        cflags += [
-          "-mips64r2",
-          "-Wa,-mips64r2",
-        ]
-        ldflags += [ "-mips64r2" ]
-      }
-    }
-
     defines += [ "_FILE_OFFSET_BITS=64" ]
 
     if (!is_android) {
@@ -446,6 +334,155 @@ config("compiler") {
   }
 }
 
+# This provides the basic options to select the target CPU and ABI.
+# It is factored out of "compiler" so that special cases can use this
+# without using everything that "compiler" brings in.  Options that
+# tweak code generation for a particular CPU do not belong here!
+# See "compiler_codegen", below.
+config("compiler_cpu_abi") {
+  cflags = []
+  ldflags = []
+
+  if (is_posix && !(is_mac || is_ios)) {
+    # CPU architecture. We may or may not be doing a cross compile now, so for
+    # simplicity we always explicitly set the architecture.
+    if (current_cpu == "x64") {
+      cflags += [
+        "-m64",
+        "-march=x86-64",
+      ]
+      ldflags += [ "-m64" ]
+    } else if (current_cpu == "x86") {
+      cflags += [ "-m32" ]
+      ldflags += [ "-m32" ]
+    } else if (current_cpu == "arm") {
+      if (is_clang && !is_android && !is_nacl) {
+        cflags += [
+          "-target",
+          "arm-linux-gnueabihf",
+        ]
+        ldflags += [
+          "-target",
+          "arm-linux-gnueabihf",
+        ]
+      }
+      if (!is_nacl) {
+        cflags += [
+          "-march=$arm_arch",
+          "-mfloat-abi=$arm_float_abi",
+        ]
+        if (arm_use_thumb) {
+          cflags += [ "-mthumb" ]
+          if (is_android && !is_clang) {
+            # Clang doesn't support this option.
+            cflags += [ "-mthumb-interwork" ]
+          }
+        }
+      }
+      if (arm_tune != "") {
+        cflags += [ "-mtune=$arm_tune" ]
+      }
+    } else if (current_cpu == "mipsel") {
+      if (mips_arch_variant == "r6") {
+        cflags += [
+          "-mips32r6",
+          "-Wa,-mips32r6",
+        ]
+        if (is_android) {
+          ldflags += [
+            "-mips32r6",
+            "-Wl,-melf32ltsmip",
+          ]
+        }
+      } else if (mips_arch_variant == "r2") {
+        cflags += [
+          "-mips32r2",
+          "-Wa,-mips32r2",
+        ]
+        if (mips_float_abi == "hard" && mips_fpu_mode != "") {
+          cflags += [ "-m$mips_fpu_mode" ]
+        }
+      } else if (mips_arch_variant == "r1") {
+        cflags += [
+          "-mips32",
+          "-Wa,-mips32",
+        ]
+      }
+
+      if (mips_dsp_rev == 1) {
+        cflags += [ "-mdsp" ]
+      } else if (mips_dsp_rev == 2) {
+        cflags += [ "-mdspr2" ]
+      }
+
+      cflags += [ "-m${mips_float_abi}-float" ]
+    } else if (current_cpu == "mips64el") {
+      if (mips_arch_variant == "r6") {
+        cflags += [
+          "-mips64r6",
+          "-Wa,-mips64r6",
+        ]
+        ldflags += [ "-mips64r6" ]
+      } else if (mips_arch_variant == "r2") {
+        cflags += [
+          "-mips64r2",
+          "-Wa,-mips64r2",
+        ]
+        ldflags += [ "-mips64r2" ]
+      }
+    }
+  }
+
+  asmflags = cflags
+}
+
+# This provides options to tweak code generation that are necessary
+# for particular Chromium code or for working around particular
+# compiler bugs (or the combination of the two).
+config("compiler_codegen") {
+  cflags = []
+
+  if (is_posix && !is_mac && !is_ios && !is_nacl) {
+    if (current_cpu == "x86") {
+      if (is_clang) {
+        cflags += [
+          # Else building libyuv gives clang's register allocator issues,
+          # see llvm.org/PR15798 / crbug.com/233709
+          "-momit-leaf-frame-pointer",
+
+          # Align the stack on 16-byte boundaries, http://crbug.com/418554.
+          "-mstack-alignment=16",
+          "-mstackrealign",
+        ]
+      }
+    } else if (current_cpu == "arm") {
+      if (is_clang) {
+        if (!is_android) {
+          # We need to disable clang's builtin assembler as it can't
+          # handle several asm files, crbug.com/124610
+          cflags += [ "-no-integrated-as" ]
+        }
+      } else {
+        # Clang doesn't support these flags.
+        cflags += [
+          # The tree-sra optimization (scalar replacement for
+          # aggregates enabling subsequent optimizations) leads to
+          # invalid code generation when using the Android NDK's
+          # compiler (r5-r7). This can be verified using
+          # webkit_unit_tests' WTF.Checked_int8_t test.
+          "-fno-tree-sra",
+
+          # The following option is disabled to improve binary
+          # size and performance in gcc 4.9.
+          "-fno-caller-saves",
+        ]
+      }
+    }
+  }
+
+  asmflags = cflags
+}
+
 config("compiler_arm_fpu") {
   if (current_cpu == "arm" && !is_ios && !is_nacl) {
     cflags = [ "-mfpu=$arm_fpu" ]