[Interest] Compiler optimisation flags on Android

[Nuno Santos]

Hi,

Below are the CFLAGS for Android 
(Qt/5.6/android_armv7/mkspecs/android-g++/qmake.conf)

I’m wondering why there are no optimisation settings for arm rather than size. 
Is there any specific reason? 

QMAKE_CFLAGS_WARN_ON    = -Wall -Wno-psabi -W
QMAKE_CFLAGS_WARN_OFF   = -Wno-psabi
equals(ANDROID_TARGET_ARCH, x86) {
    QMAKE_CFLAGS_RELEASE                   = -O2
    QMAKE_CFLAGS_RELEASE_WITH_DEBUGINFO    = -g -O2
    QMAKE_CFLAGS_DEBUG                     = -g
} else: equals(ANDROID_TARGET_ARCH, x86_64) {
    QMAKE_CFLAGS_RELEASE                   = -O2
    QMAKE_CFLAGS_RELEASE_WITH_DEBUGINFO    = -g -O2
    QMAKE_CFLAGS_DEBUG                     = -g
} else: equals(ANDROID_TARGET_ARCH, mips) {
    QMAKE_CFLAGS_RELEASE                   = -O2
    QMAKE_CFLAGS_RELEASE_WITH_DEBUGINFO    = -g -O2
    QMAKE_CFLAGS_DEBUG                     = -g -fno-omit-frame-pointer
} else: equals(ANDROID_TARGET_ARCH, mips64) {
    QMAKE_CFLAGS_RELEASE                   = -O2
    QMAKE_CFLAGS_RELEASE_WITH_DEBUGINFO    = -g -O2
    QMAKE_CFLAGS_DEBUG                     = -g -fno-omit-frame-pointer
} else: equals(ANDROID_TARGET_ARCH, arm64-v8a) {
    QMAKE_CFLAGS_RELEASE                   = -O2
    QMAKE_CFLAGS_RELEASE_WITH_DEBUGINFO    = -g -O2
    QMAKE_CFLAGS_DEBUG                     = -g -fno-omit-frame-pointer
} else { # arm
    QMAKE_CFLAGS_RELEASE                   = -Os -fomit-frame-pointer 
-fno-strict-aliasing -finline-limit=64
    QMAKE_CFLAGS_RELEASE_WITH_DEBUGINFO    = -g -Os -fomit-frame-pointer 
-fno-strict-aliasing -finline-limit=64
    QMAKE_CFLAGS_DEBUG                     = -g -marm -O0 
-fno-omit-frame-pointer
    equals(ANDROID_TARGET_ARCH, armeabi):if(equals(NDK_TOOLCHAIN_VERSION, 
4.8)|equals(NDK_TOOLCHAIN_VERSION, 4.9)) {
        DEFINES += QT_OS_ANDROID_GCC_48_WORKAROUND
    } else {
        QMAKE_CFLAGS_RELEASE += -mthumb
        QMAKE_CFLAGS_RELEASE_WITH_DEBUGINFO += -mthumb
    }
}

Regards,

Nuno
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