problems with the AArch64 inline Assembler
lazarus / 66-Unix

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derMischka81 · 2021-02-16 12:28

I use the inline Asssembler on my RPi3 with 64Bit OS.

I have problems with the following inline Assembler instruction

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i asm  add
x1, x1, x7, lsl #3end; 
The Instruction should do the following thing:

x1 := x1 + (x7 shl 3)

but if I compile and check the results inklusive the assembly window I
can see that the BarrelShift (lsl #3) is missing.


The Next Problem is a branch to a Object-function.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i TTestObj1.t
estproc;beginend; TTestObj2.asmprob;nostackframe;assembler;asm  stp
x0, x30, [sp, #-16]!   ldr x0, [x0, FTestObj1]  bl
TTestObj1.testproc   ldp x0, x30 [sp], #16end; 
The Branch-Value/Address is not correct --> jumps to the branch line
self (infinite loop)

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Zvoni · 2021-02-16 14:33

I was under the impression, that the ADD in Assembly has three
operands: Destination, Source1, Source2
You have 4 operands

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PascalDragon · 2021-02-17 08:43

Quote from: derMischka81 on February 16, 2021, 01:28:19 pmI use the
inline Asssembler on my RPi3 with 64Bit OS.

I have problems with the following inline Assembler instruction

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i asm  add
x1, x1, x7, lsl #3end; 
The Instruction should do the following thing:

x1 := x1 + (x7 shl 3)

but if I compile and check the results inklusive the assembly window I
can see that the BarrelShift (lsl #3) is missing.
You are aware that I as a compiler developer had already replied to
this in on your thread in German forum? And that you should report
this on the bug tracker?

Quote from: derMischka81 on February 16, 2021, 01:28:19 pmThe Next
Problem is a branch to a Object-function.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i TTestObj1.t
estproc;beginend; TTestObj2.asmprob;nostackframe;assembler;asm  stp
x0, x30, [sp, #-16]!   ldr x0, [x0, FTestObj1]  bl
TTestObj1.testproc   ldp x0, x30 [sp], #16end; 
The Branch-Value/Address is not correct --> jumps to the branch line
self (infinite loop)

I think you better use a combination of ADRP and ADR to load the
address into a register and branch to that. What exactly the assembler
reader generates for your code I'd need to check.

Quote from: Zvoni on February 16, 2021, 03:33:55 pmI was under the
impression, that the ADD in Assembly has three operands: Destination,
Source1, Source2
You have 4 operands

The ADD instruction (among others) can also have an additional shift
left as fourth parameter. See for example here.

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Jonas Maebe · 2021-02-17 13:26

Quote from: derMischka81 on February 16, 2021, 01:28:19 pmI use the
inline Asssembler on my RPi3 with 64Bit OS.

I have problems with the following inline Assembler instruction

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i asm  add
x1, x1, x7, lsl #3end; This bug is fixed in trunk and fixes_3_2.

QuoteCode: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i TTestObj1.t
estproc;beginend; TTestObj2.asmprob;nostackframe;assembler;asm  stp
x0, x30, [sp, #-16]!   ldr x0, [x0, FTestObj1]  bl
TTestObj1.testproc   ldp x0, x30 [sp], #16end; While not yet
supported, for now this at least gives a compilation error rather than
resulting in invalid code. The compiler does not yet parse "ldr x0,
[x0, FTestObj1]" correctly either though (it seems to ignore the
"FTestObj1"; even if it does not exist, no compilation error is
printed).

The RTL uses very little AArch64 inline assembly and since it's a new
architecture, existing inline assembly tests are not checked for it
(they would have to be translated first). So there are probably quite
a few more bugs in its assembler reader...