[OE-core] [PATCH 01/12] tune/arm: Set -mtune instead of -mcpu

Andre McCurdy armccurdy at gmail.com
Wed Jun 6 23:42:45 UTC 2018 

On Wed, Jun 6, 2018 at 3:43 PM, Khem Raj <raj.khem at gmail.com> wrote:
> On Wed, Jun 6, 2018 at 3:15 PM, Andre McCurdy <armccurdy at gmail.com> wrote:
>> On Wed, Jun 6, 2018 at 2:37 PM, Khem Raj <raj.khem at gmail.com> wrote:
>>> -march option is already used to select the base architecture
>>> therefore using -mcpu which infact will reset march+mtune can
>>> cause conflicts,
>>
>> I think we need to at least understand how and why these conflicts
>> have started to occur with gcc 8. The tuning files themselves don't
>> contain any conflicts so the conflict must be coming from somewhere
>> else. Do we know where?
>
> I explained it in previous emails as well, mcpu is a combination of march+mtune
> how it reduces to these values depends on mcpu value. e.g. setting
> mcpu=cortex-a7
> would mean setting march=armv7ve and mtune to cortex-a7 internally
> along with using code generator to use instructions available for that
> cpu, thats why it errors out since it does not know which march to
> use.
> when we override one of these values on cmdline which we do then this can cause
> the errors, these errors were happening before too see valgrind patch
> its that gcc8 is catching more cases.

The -mcpu, -march and -mtune options are not new and gcc 6 and 7 catch
the same conflicts. It doesn't make sense that gcc8 is just catching
more issues.

The valgrind case is not a good example. The conflict there comes
because we leak CFLAGS intended for the target into Makefiles which
valgrind uses to build test apps which are intended to only run under
valgrind (ie NOT directly on the target). The real fix there would be
to prevent the target specific flags being passed to build for those
few valgrind test apps.

> example is gcc-runtime/libstdc++ which deducts arch flags based on
> configure options
> and we do not pass narrow mcpu option to it since we build SDKs which
> do not target
> just one particular sub-family of cpu but rather a sub arch
> do not pass --with-cpu then it enforces some lowest common
> denominator. When we say -mcpu then we
> are actually asking the code to be generated for that particular CPU.

If we are trying to build something which is reusable across multiple
machines with the same architecture then it's a bug to be passing
machine specific CFLAGS. Making the machine specific CFLAGS more
generic is not the right solution.

Anyway, I suspect the real issue here is that when we build gcc to run
on the target we currently configure using "--with-arch=armv7-a" for
both armv7a and armv7ve. It was done that way deliberately to try to
avoid rebuilds when switching between armv7a and armv7ve machines,
although thinking about that now I'm not sure it makes so much sense.
Does your original problem go away if you simply change:

  EXTRA_OECONF_append_armv7ve = " --with-arch=armv7-a"

to

  EXTRA_OECONF_append_armv7ve = " --with-arch=armv7ve"

in gcc-target.inc ?

>>
>> This patch is potentially going to hide bugs in cases where components
>> try to provide their own CPU specific flags rather than fully
>> respecting the flags set by OE. Generally we want to make those cases
>> fail so that we can debug and fix them.
>>
>
> No it wont. they can still do that. Last option wins so nothing changes there.

The thing that changes is that after your patch, gcc will no longer
report a conflict!

> and in many cases it should be able to override specific flags for
> specific packages
> OE is a fall back for general default case.
>
> A good change this does is that code is targeted for bigger base arch
> e.g. armv7-a
> and not for cortex-a8 but its tuned to run better on cortex-a8 when we
> use -mtune
> it will still run on other armv7-a based CPUs, so right now when we
> say our package
> arch is arm7ve but then use -mcpu=cortex-a7 we are actually doing wrong thing
> this should have meant package arch to be cortex-a7 as well. Now this
> will be more
> inline as well.
>
>
>>> therefore setting just mtune here will ensure
>>> that the code is optimized for the given tune as is the intention
>>> of mcpu, however with one advantage, it will be targetting broader
>>> march value so can be useful for pre-compiled objects where they
>>> can be run on wider subset
>>>
>>> This also fixed occasional conflicts like
>>>
>>> cc1: error: switch -mcpu=cortex-a7 conflicts with -march=armv7-a switch [-Werror]
>>>
>>> which is possible combination in some case for packages in OE
>>>
>>> Signed-off-by: Khem Raj <raj.khem at gmail.com>
>>> ---
>>>  meta/conf/machine/include/tune-arm1136jf-s.inc   | 2 +-
>>>  meta/conf/machine/include/tune-arm920t.inc       | 2 +-
>>>  meta/conf/machine/include/tune-arm926ejs.inc     | 2 +-
>>>  meta/conf/machine/include/tune-arm9tdmi.inc      | 2 +-
>>>  meta/conf/machine/include/tune-cortexa15.inc     | 2 +-
>>>  meta/conf/machine/include/tune-cortexa17.inc     | 2 +-
>>>  meta/conf/machine/include/tune-cortexa5.inc      | 2 +-
>>>  meta/conf/machine/include/tune-cortexa7.inc      | 2 +-
>>>  meta/conf/machine/include/tune-cortexa8.inc      | 2 +-
>>>  meta/conf/machine/include/tune-cortexa9.inc      | 2 +-
>>>  meta/conf/machine/include/tune-ep9312.inc        | 2 +-
>>>  meta/conf/machine/include/tune-iwmmxt.inc        | 2 +-
>>>  meta/conf/machine/include/tune-strongarm1100.inc | 2 +-
>>>  meta/conf/machine/include/tune-thunderx.inc      | 2 +-
>>>  meta/conf/machine/include/tune-xscale.inc        | 2 +-
>>>  15 files changed, 15 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/meta/conf/machine/include/tune-arm1136jf-s.inc b/meta/conf/machine/include/tune-arm1136jf-s.inc
>>> index c5de63e1cc..02114284e0 100644
>>> --- a/meta/conf/machine/include/tune-arm1136jf-s.inc
>>> +++ b/meta/conf/machine/include/tune-arm1136jf-s.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv6hf"
>>>  require conf/machine/include/arm/arch-armv6.inc
>>>
>>>  TUNEVALID[arm1136jfs] = "Enable arm1136jfs specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'arm1136jfs', ' -mcpu=arm1136jf-s', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'arm1136jfs', ' -mtune=arm1136jf-s', '', d)}"
>>>
>>>  AVAILTUNES += "arm1136jfs"
>>>  ARMPKGARCH_tune-arm1136jfs = "arm1136jfs"
>>> diff --git a/meta/conf/machine/include/tune-arm920t.inc b/meta/conf/machine/include/tune-arm920t.inc
>>> index c6e74b6772..5e6d4cbd91 100644
>>> --- a/meta/conf/machine/include/tune-arm920t.inc
>>> +++ b/meta/conf/machine/include/tune-arm920t.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv4t"
>>>  require conf/machine/include/arm/arch-armv4.inc
>>>
>>>  TUNEVALID[arm920t] = "Enable arm920t specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'arm920t', ' -mcpu=arm920t', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'arm920t', ' -mtune=arm920t', '', d)}"
>>>
>>>  AVAILTUNES += "arm920t"
>>>  ARMPKGARCH_tune-arm920t = "arm920t"
>>> diff --git a/meta/conf/machine/include/tune-arm926ejs.inc b/meta/conf/machine/include/tune-arm926ejs.inc
>>> index 81bcda339b..dddccaaae9 100644
>>> --- a/meta/conf/machine/include/tune-arm926ejs.inc
>>> +++ b/meta/conf/machine/include/tune-arm926ejs.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv5te"
>>>  require conf/machine/include/arm/arch-armv5-dsp.inc
>>>
>>>  TUNEVALID[arm926ejs] = "Enable arm926ejs specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'arm926ejs', ' -mcpu=arm926ej-s', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'arm926ejs', ' -mtune=arm926ej-s', '', d)}"
>>>
>>>  AVAILTUNES += "arm926ejs"
>>>  ARMPKGARCH_tune-arm926ejs = "arm926ejs"
>>> diff --git a/meta/conf/machine/include/tune-arm9tdmi.inc b/meta/conf/machine/include/tune-arm9tdmi.inc
>>> index e9c2b8fcf5..ebac472c5b 100644
>>> --- a/meta/conf/machine/include/tune-arm9tdmi.inc
>>> +++ b/meta/conf/machine/include/tune-arm9tdmi.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv4t"
>>>  require conf/machine/include/arm/arch-armv4.inc
>>>
>>>  TUNEVALID[arm9tdmi] = "Enable arm9tdmi specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'arm9tdmi', ' -mcpu=arm9tdmi', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'arm9tdmi', ' -mtune=arm9tdmi', '', d)}"
>>>
>>>  AVAILTUNES += "arm9tdmi"
>>>  ARMPKGARCH_tune-arm9tdmi = "arm9tdmi"
>>> diff --git a/meta/conf/machine/include/tune-cortexa15.inc b/meta/conf/machine/include/tune-cortexa15.inc
>>> index 25e99f93d7..0636306e2f 100644
>>> --- a/meta/conf/machine/include/tune-cortexa15.inc
>>> +++ b/meta/conf/machine/include/tune-cortexa15.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv7vethf-neon"
>>>  require conf/machine/include/arm/arch-armv7ve.inc
>>>
>>>  TUNEVALID[cortexa15] = "Enable Cortex-A15 specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa15', ' -mcpu=cortex-a15', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa15', ' -mtune=cortex-a15', '', d)}"
>>>
>>>  # Little Endian base configs
>>>  AVAILTUNES += "cortexa15 cortexa15t cortexa15-neon cortexa15t-neon cortexa15-neon-vfpv4 cortexa15t-neon-vfpv4"
>>> diff --git a/meta/conf/machine/include/tune-cortexa17.inc b/meta/conf/machine/include/tune-cortexa17.inc
>>> index 40392f9bcc..f9774b8b8e 100644
>>> --- a/meta/conf/machine/include/tune-cortexa17.inc
>>> +++ b/meta/conf/machine/include/tune-cortexa17.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv7vethf-neon"
>>>  require conf/machine/include/arm/arch-armv7ve.inc
>>>
>>>  TUNEVALID[cortexa17] = "Enable Cortex-A17 specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa17', ' -mcpu=cortex-a17', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa17', ' -mtune=cortex-a17', '', d)}"
>>>
>>>  # Little Endian base configs
>>>  AVAILTUNES += "cortexa17 cortexa17t cortexa17-neon cortexa17t-neon cortexa17-neon-vfpv4 cortexa17t-neon-vfpv4"
>>> diff --git a/meta/conf/machine/include/tune-cortexa5.inc b/meta/conf/machine/include/tune-cortexa5.inc
>>> index 1f0cda6640..1ececf9621 100644
>>> --- a/meta/conf/machine/include/tune-cortexa5.inc
>>> +++ b/meta/conf/machine/include/tune-cortexa5.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv7athf-neon"
>>>  require conf/machine/include/arm/arch-armv7a.inc
>>>
>>>  TUNEVALID[cortexa5] = "Enable Cortex-A5 specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa5', ' -mcpu=cortex-a5', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa5', ' -mtune=cortex-a5', '', d)}"
>>>
>>>  # Little Endian base configs
>>>  AVAILTUNES += "cortexa5 cortexa5t cortexa5-neon cortexa5t-neon"
>>> diff --git a/meta/conf/machine/include/tune-cortexa7.inc b/meta/conf/machine/include/tune-cortexa7.inc
>>> index 52415d9c8b..08dd039338 100644
>>> --- a/meta/conf/machine/include/tune-cortexa7.inc
>>> +++ b/meta/conf/machine/include/tune-cortexa7.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv7vethf-neon"
>>>  require conf/machine/include/arm/arch-armv7ve.inc
>>>
>>>  TUNEVALID[cortexa7] = "Enable Cortex-A7 specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa7', ' -mcpu=cortex-a7', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa7', ' -mtune=cortex-a7', '', d)}"
>>>
>>>  # Little Endian base configs
>>>  AVAILTUNES += "cortexa7 cortexa7t cortexa7-neon cortexa7t-neon cortexa7-neon-vfpv4 cortexa7t-neon-vfpv4"
>>> diff --git a/meta/conf/machine/include/tune-cortexa8.inc b/meta/conf/machine/include/tune-cortexa8.inc
>>> index 8ee8de97f1..cdcb1c7d59 100644
>>> --- a/meta/conf/machine/include/tune-cortexa8.inc
>>> +++ b/meta/conf/machine/include/tune-cortexa8.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv7athf-neon"
>>>  require conf/machine/include/arm/arch-armv7a.inc
>>>
>>>  TUNEVALID[cortexa8] = "Enable Cortex-A8 specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa8', ' -mcpu=cortex-a8', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa8', ' -mtune=cortex-a8', '', d)}"
>>>
>>>  # Little Endian base configs
>>>  AVAILTUNES += "cortexa8 cortexa8t cortexa8-neon cortexa8t-neon"
>>> diff --git a/meta/conf/machine/include/tune-cortexa9.inc b/meta/conf/machine/include/tune-cortexa9.inc
>>> index 0cf323c960..620178d18a 100644
>>> --- a/meta/conf/machine/include/tune-cortexa9.inc
>>> +++ b/meta/conf/machine/include/tune-cortexa9.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv7athf-neon"
>>>  require conf/machine/include/arm/arch-armv7a.inc
>>>
>>>  TUNEVALID[cortexa9] = "Enable Cortex-A9 specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa9', ' -mcpu=cortex-a9', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexa9', ' -mtune=cortex-a9', '', d)}"
>>>
>>>  # Little Endian base configs
>>>  AVAILTUNES += "cortexa9 cortexa9t cortexa9-neon cortexa9t-neon"
>>> diff --git a/meta/conf/machine/include/tune-ep9312.inc b/meta/conf/machine/include/tune-ep9312.inc
>>> index 84ca528d6d..897b904cd1 100644
>>> --- a/meta/conf/machine/include/tune-ep9312.inc
>>> +++ b/meta/conf/machine/include/tune-ep9312.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "ep9312"
>>>  require conf/machine/include/arm/arch-armv4.inc
>>>
>>>  TUNEVALID[ep9312] = "Enable Intel PXA27x specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'ep9312', ' -march=ep9312 -mcpu=ep9312', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'ep9312', ' -march=ep9312 -mtune=ep9312', '', d)}"
>>>
>>>  AVAILTUNES += "ep9312"
>>>  ARMPKGARCH_tune-ep9312 = "ep9312"
>>> diff --git a/meta/conf/machine/include/tune-iwmmxt.inc b/meta/conf/machine/include/tune-iwmmxt.inc
>>> index f27423cb2e..15cce8d3c5 100644
>>> --- a/meta/conf/machine/include/tune-iwmmxt.inc
>>> +++ b/meta/conf/machine/include/tune-iwmmxt.inc
>>> @@ -6,7 +6,7 @@ DEFAULTTUNE ?= "iwmmxt"
>>>  require conf/machine/include/arm/arch-armv5-dsp.inc
>>>
>>>  TUNEVALID[iwmmxt] = "Enable Intel PXA27x specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'iwmmxt', ' -march=iwmmxt -mcpu=iwmmxt', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'iwmmxt', ' -march=iwmmxt -mtune=iwmmxt', '', d)}"
>>>
>>>  AVAILTUNES += "iwmmxt"
>>>  ARMPKGARCH_tune-iwmmxt = "iwmmxt"
>>> diff --git a/meta/conf/machine/include/tune-strongarm1100.inc b/meta/conf/machine/include/tune-strongarm1100.inc
>>> index 80cfb8ab8a..7b2fa8e3ab 100644
>>> --- a/meta/conf/machine/include/tune-strongarm1100.inc
>>> +++ b/meta/conf/machine/include/tune-strongarm1100.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv4"
>>>  require conf/machine/include/arm/arch-armv4.inc
>>>
>>>  TUNEVALID[strongarm] = "Enable Strongarm 1100 series processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'strongarm', ' -mcpu=strongarm1100', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'strongarm', ' -mtune=strongarm1100', '', d)}"
>>>
>>>  AVAILTUNES += "strongarm"
>>>  ARMPKGARCH_tune-strongarm = "strongarm"
>>> diff --git a/meta/conf/machine/include/tune-thunderx.inc b/meta/conf/machine/include/tune-thunderx.inc
>>> index 3d43b0f7e5..e77d1cdd2d 100644
>>> --- a/meta/conf/machine/include/tune-thunderx.inc
>>> +++ b/meta/conf/machine/include/tune-thunderx.inc
>>> @@ -5,7 +5,7 @@ AVAILTUNES += "thunderx thunderx_be"
>>>
>>>  TUNEVALID[thunderx] = "Enable instructions for Cavium ThunderX"
>>>
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'thunderx', ' -mcpu=thunderx ', '',d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'thunderx', ' -mtune=thunderx ', '',d)}"
>>>
>>>  ARMPKGARCH_tune-thunderx ?= "thunderx"
>>>  ARMPKGARCH_tune-thunderx_be ?= "thunderx_be"
>>> diff --git a/meta/conf/machine/include/tune-xscale.inc b/meta/conf/machine/include/tune-xscale.inc
>>> index 0d07333955..2a0610fddf 100644
>>> --- a/meta/conf/machine/include/tune-xscale.inc
>>> +++ b/meta/conf/machine/include/tune-xscale.inc
>>> @@ -3,7 +3,7 @@ DEFAULTTUNE ?= "armv5te"
>>>  require conf/machine/include/arm/arch-armv5-dsp.inc
>>>
>>>  TUNEVALID[xscale] = "Enable PXA255/PXA26x Xscale specific processor optimizations"
>>> -TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'xscale', ' -mcpu=xscale', '', d)}"
>>> +TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'xscale', ' -mtune=xscale', '', d)}"
>>>
>>>  AVAILTUNES += "xscale"
>>>  ARMPKGARCH_tune-xscale = "xscale"
>>> --
>>> 2.17.1
>>>
>>> --
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