[fpc-devel] Trunk does not build on AArch64
J. Gareth Moreton
gareth at moreton-family.com
Sun Oct 18 12:25:11 CEST 2020
I can't remember for sure - it might have been 3.0.4, so I'm probably
asking for trouble now. When I get back later I'll check for sure and
try a few things and get back to you. At least it's confirmed that it
actually did not compile!
For the curious, I'm looking to implement the optimisation of converting
a division by a constant into a multiplication and a shift for AArch64,
inspired by me playing around with my own assembly-written generator
function in the other e-mail thread. I made the comment about ADDS,
forgetting about suffixes, because of how 'magic add' is handled when
required (e.g. when dividing by 7 for 32-bit).
Gareth aka. Kit
On 18/10/2020 10:31, Sven Barth wrote:
> Am 18.10.2020 um 11:15 schrieb J. Gareth Moreton:
>> Hi Sven - thanks for the quick check. I'm out of the house currently
>> so I can't try it out immediately, but I'll try it out later this
>> evening. By the way, both my source and target are aarch64-linux
>> (I'm using the prototype aarch64 build of the Raspberry Pi OS,
>> athough I have an SD card with the standard 32-bit Arm Raspian as well).
> So you used 3.2.0 aarch64-linux as starting compiler? (though the
> question isn't important anymore as the problem was somewhere else)
>> In regards to it not supporting inline assembly, it might only be
>> applicable to FPC 3.2.x, as I tried to write some customised assembly
>> language but was getting unrecognised opcode errors for instructions
>> that definitely exist (like LDR).
> 3.2.0 also supports inline assembly for aarch64. And LDR works as well
> as the following code in the Rtti unit from 3.2.0 shows:
> === code begin ===
> RawThunkPlaceholderProc = $8765876587658765;
> RawThunkPlaceholderContext = $4321432143214321;
> TRawThunkProc = PtrUInt;
> TRawThunkContext = PtrUInt;
> procedure RawThunk; assembler; nostackframe;
> ldr x16, .LProc
> ldr x0, .LContext
> br x16
> .quad RawThunkPlaceholderProc
> .quad RawThunkPlaceholderContext
> === code end ===
> So you probably either used something that's definitely not supposed
> to be supported or something that the assembly reader does not yet
> handle correctly (e.g. I had to fix 3.1.1 so that the code above is
> handled correctly)
> Thus if you have such code and it doesn't work please report it.
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