Re: [PATCH 3/3] MdePkg/BaseSynchronizationLib: Remove inline X86 assembly code

["Kinney, Michael D" <michael.d.kinney@intel.com>]

Liming,

I agree .nasm files replacing .S/.asm files.  But the use of inline
assembly in C files for some primitives does produce much smaller/faster
code.

I would prefer that this BZ identify the specific functions that you
think would provide better maintainability with no impact to size
or performance.

Thanks,

Mike

> -----Original Message-----
> From: Gao, Liming
> Sent: Tuesday, March 5, 2019 1:33 PM
> To: afish@apple.com; Zhang, Shenglei
> <shenglei.zhang@intel.com>
> Cc: edk2-devel-01 <edk2-devel@lists.01.org>; Kinney,
> Michael D <michael.d.kinney@intel.com>
> Subject: RE: [edk2] [PATCH 3/3]
> MdePkg/BaseSynchronizationLib: Remove inline X86
> assembly code
> 
> Andrew:
>   BZ 1163 is to remove inline X86 assembly code in C
> source file. But, this patch is wrong. I have gave my
> comments to update this patch.
> 
>   The change is to reduce the duplicated
> implementation. It will be good on the code maintain.
> Recently, one patch has to update .c and .nasm both.
> Please see https://lists.01.org/pipermail/edk2-
> devel/2019-February/037165.html. Beside this change, I
> propose to remove all GAS assembly code for IA32 and
> X64 arch. After those change, the patch owner will
> collect the impact of the image size.
> 
> Thanks
> Liming
> > -----Original Message-----
> > From: afish@apple.com [mailto:afish@apple.com]
> > Sent: Tuesday, March 5, 2019 12:58 PM
> > To: Zhang, Shenglei <shenglei.zhang@intel.com>
> > Cc: edk2-devel-01 <edk2-devel@lists.01.org>; Kinney,
> Michael D <michael.d.kinney@intel.com>; Gao, Liming
> <liming.gao@intel.com>
> > Subject: Re: [edk2] [PATCH 3/3]
> MdePkg/BaseSynchronizationLib: Remove inline X86
> assembly code
> >
> > Shenglei,
> >
> > I was confused by the names of these patches. From a
> C point of view this is inline assembly:
> >
> > VOID
> > EFIAPI
> > CpuBreakpoint (
> > VOID
> > )
> > {
> > __asm__ __volatile__ ("int $3");
> > }
> >
> > These patches seem to be removing GAS and MASM
> assembly files, but not the inline assembly *.c files?
> >
> > We don't want to remove the inline assembly from the
> BaseLib as that could have size, performance, and
> compiler optimization impact.
> >
> > For example CpuBreakpoint() for clang with LTO would
> end up inlining a single byte. For i385 a call to
> assembler would be 5 bytes at each
> > call location plus the overhead of the function. So
> that is a size increase and a performance overhead. For
> a C complier calling an assembly
> > function is a serializing event an that can restrict
> optimizations. Thus having some limited inline assembly
> support is very useful.
> >
> > Thanks,
> >
> > Andrew Fish
> >
> > > On Mar 4, 2019, at 5:40 PM, Shenglei Zhang
> <shenglei.zhang@intel.com> wrote:
> > >
> > > MdePkg BaseSynchronizationLib still uses the inline
> X86 assembly code
> > > in C code files.It should be updated to consume
> nasm only.
> > > https://bugzilla.tianocore.org/show_bug.cgi?id=1163
> > >
> > > Cc: Michael D Kinney <michael.d.kinney@intel.com>
> > > Cc: Liming Gao <liming.gao@intel.com>
> > > Contributed-under: TianoCore Contribution Agreement
> 1.1
> > > Signed-off-by: Shenglei Zhang
> <shenglei.zhang@intel.com>
> > > ---
> > >
> .../Library/BaseSynchronizationLib/BaseSynchronizationL
> ib.inf   | 2 --
> > > 1 file changed, 2 deletions(-)
> > >
> > > diff --git
> a/MdePkg/Library/BaseSynchronizationLib/BaseSynchroniza
> tionLib.inf
> >
> b/MdePkg/Library/BaseSynchronizationLib/BaseSynchroniza
> tionLib.inf
> > > index 32414b29fa..719dc1938d 100755
> > > ---
> a/MdePkg/Library/BaseSynchronizationLib/BaseSynchroniza
> tionLib.inf
> > > +++
> b/MdePkg/Library/BaseSynchronizationLib/BaseSynchroniza
> tionLib.inf
> > > @@ -75,13 +75,11 @@
> > >
> > > [Sources.ARM]
> > > Synchronization.c
> > > -  Arm/Synchronization.asm       | RVCT
> > > Arm/Synchronization.S         | GCC
> > >
> > > [Sources.AARCH64]
> > > Synchronization.c
> > > AArch64/Synchronization.S     | GCC
> > > -  AArch64/Synchronization.asm   | MSFT
> > >
> > > [Packages]
> > > MdePkg/MdePkg.dec
> > > --
> > > 2.18.0.windows.1
> > >
> > > _______________________________________________
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> > > edk2-devel@lists.01.org
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