Upgrade x86 gcc to 4.9 and disable devirtualization.

Also filter out gcc-only flags -Wno-clobbered and -fno-devirtualize
when compiled with clang/llvm.

BUG: 19872411
Change-Id: I6de57583be04da607f569df65e93531787dbb789

core/clang/config.mk

@@ -68,10 +68,13 @@ CLANG_CONFIG_UNKNOWN_CFLAGS := \
   -finline-functions \
   -finline-limit=64 \
   -fno-canonical-system-headers \
+  -Wno-clobbered \
+  -fno-devirtualize \
   -fno-tree-sra \
   -fprefetch-loop-arrays \
   -funswitch-loops \
   -Wmaybe-uninitialized \
+  -Wno-error=clobbered \
   -Wno-error=maybe-uninitialized \
   -Wno-error=unused-but-set-parameter \
   -Wno-error=unused-but-set-variable \

core/combo/TARGET_linux-x86.mk

@@ -23,10 +23,10 @@ TARGET_$(combo_2nd_arch_prefix)ARCH_VARIANT := x86
 endif
 
 # Decouple NDK library selection with platform compiler version
-$(combo_2nd_arch_prefix)TARGET_NDK_GCC_VERSION := 4.8
+$(combo_2nd_arch_prefix)TARGET_NDK_GCC_VERSION := 4.9
 
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
-$(combo_2nd_arch_prefix)TARGET_GCC_VERSION := 4.8
+$(combo_2nd_arch_prefix)TARGET_GCC_VERSION := 4.9
 else
 $(combo_2nd_arch_prefix)TARGET_GCC_VERSION := $(TARGET_GCC_VERSION_EXP)
 endif
@@ -97,6 +97,10 @@ $(combo_2nd_arch_prefix)TARGET_GLOBAL_CFLAGS += \
 			-include $(android_config_h) \
 			-I $(dir $(android_config_h))
 
+# Work around gcc 4.9 devirtualization bug, https://b.corp.google.com/19872411.
+$(combo_2nd_arch_prefix)TARGET_GLOBAL_CFLAGS += \
+			-fno-devirtualize \
+
 $(combo_2nd_arch_prefix)TARGET_GLOBAL_CFLAGS += $(arch_variant_cflags)
 
 ifeq ($(ARCH_X86_HAVE_SSSE3),true)   # yes, really SSSE3, not SSE3!

core/combo/TARGET_linux-x86_64.mk

@@ -26,7 +26,7 @@ endif
 TARGET_NDK_GCC_VERSION := 4.9
 
 ifeq ($(strip $(TARGET_GCC_VERSION_EXP)),)
-TARGET_GCC_VERSION := 4.8
+TARGET_GCC_VERSION := 4.9
 else
 TARGET_GCC_VERSION := $(TARGET_GCC_VERSION_EXP)
 endif
@@ -93,6 +93,10 @@ TARGET_GLOBAL_CFLAGS += \
 			-no-canonical-prefixes \
 			-fno-canonical-system-headers
 
+# Work around gcc 4.9 devirtualization bug, https://b.corp.google.com/19872411.
+TARGET_GLOBAL_CFLAGS += \
+			-fno-devirtualize \
+
 # Help catch common 32/64-bit errors.
 TARGET_GLOBAL_CFLAGS += \
     -Werror=pointer-to-int-cast \