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IDProjectCategoryView StatusLast Update
0014862FPCCompilerpublic2010-11-26 13:57
ReporterEnigmaAssigned ToJonas Maebe 
Status closedResolutionfixed 
PlatformWindowsOSVistaOS Versionx64
Product Version2.5.1Product Build 
Target VersionFixed in Version2.6.0 
Summary0014862: Few Intel x64 assembler bugs
DescriptionI've noticed few assembler bugs, means bugs that occur when I use some "asm end;"... Everything here is related to Intel assembler type, x64.

1. Compiler allows to write such code
but "pushad" is instruction of x32 assembler, in x64 there is no pushad/pushaq, there is no instructions that allows to push all registers to stack. Compiler generates $60 opcode for this command, but in WinDbg this opcode is known as invalid.
2. Same as 0000001 but with "popad"
3. Compiler allows to do this:
but in x64 assembler there is no such commands too. For x64 there are:
4. Also one bug... If I implement such record:
  TOwnRecord = record
    first_param : qword;
    second_param : qword;
    third_param : qword;
  param : TOwnRecord;
then in assembler code I do the following:
  lea rax, [rip + param]
  mov TOwnRecord(rax).first_param, rcx
after compiling, the second line is changing from qword to dword, means, in WinDbg the second line looks:
mov dword ptr [rax + 0], ecx
but not as I require:
mov qword ptr [rax + 0], rcx
TagsNo tags attached.
Fixed in Revision15546
Attached Files


related to 0016622 closedFlorian Invalid REX prefix 



2009-10-22 14:50

reporter   ~0031578

one note also, when I want to insert "int 3" asm instruction, compiler generate opcode "$CD $03", but the better way is to use "$CC" opcode. It is smaller and could be used as a breakpoint for debuggers.

Currently, int 3 that FPC generates, with "$CD $03" opcode, allows to break in debugger, but WinDbg works incorrectly to step after this instruction.


2009-10-22 14:52

reporter   ~0031580

One more note, in Windows x64 application, if I write asm:
  sub rax, qword ptr [rcx]
comiler anyway compiles it to
  sub eax, dword ptr [rcx]
i.e. translate my qword to dword and rcx to ecx.

Jonas Maebe

2009-10-22 15:03

manager   ~0031582

The correct mnemonic for opcode $CC is int3. This is different from "int 3", with a space.


2009-10-26 09:33

reporter   ~0031675

Last edited: 2009-10-26 09:34

Ahhh, need to enter "int3"... wow... understand.. nice thing, thanks!

Also have found few bugs in assembler (x64).

if I try to write
  mov rax, fs:[rcx]
  mov rax, gs:[rcx]

compiler translate both these to just:

  mov rax, [rcx]

without fs or gs.
PS: "mov rax, [rcx]" is the same as "mov rax, ds:[rcx]"

Jonas Maebe

2009-10-26 09:41

manager   ~0031676

The Intel assembler mode is used very little for 64 bit (because there is no existing Delphi code that uses it), so in a sense it's unfortunately logical that it still contains a lot of bugs...


2009-10-26 11:12

reporter   ~0031678

Sure, it is little specific.. Do you want me to post any other asm bugs here (if I find more..), or stop posting?

The higher deal for x64 application is supporting exceptions... Do you know, is this in progress, can we wait it soon or it is low priority?

Jonas Maebe

2009-10-26 11:27

manager   ~0031679

It's best to open a separate bug report per problem. If someone fixes one problem, then they can immediately close that bug.

I don't know the status of dealing with exception handling in win64. I'm not involved in the Windows support.

Jonas Maebe

2010-07-10 18:46

manager   ~0039240

Issues 1 to 3 were fixed in r15546

Issue 4 is tracked in 0016622

The issues in comments 0031580 and 0031675 seem to have been resolved already by another fix in the mean time.

Issue History

Date Modified Username Field Change
2009-10-21 08:57 Enigma New Issue
2009-10-22 14:50 Enigma Note Added: 0031578
2009-10-22 14:52 Enigma Note Added: 0031580
2009-10-22 15:03 Jonas Maebe Note Added: 0031582
2009-10-26 09:33 Enigma Note Added: 0031675
2009-10-26 09:34 Enigma Note Edited: 0031675
2009-10-26 09:41 Jonas Maebe Note Added: 0031676
2009-10-26 11:12 Enigma Note Added: 0031678
2009-10-26 11:27 Jonas Maebe Note Added: 0031679
2010-07-10 18:43 Jonas Maebe Relationship added related to 0016622
2010-07-10 18:46 Jonas Maebe Fixed in Revision => 15546
2010-07-10 18:46 Jonas Maebe Status new => resolved
2010-07-10 18:46 Jonas Maebe Fixed in Version => 2.5.1
2010-07-10 18:46 Jonas Maebe Resolution open => fixed
2010-07-10 18:46 Jonas Maebe Assigned To => Jonas Maebe
2010-07-10 18:46 Jonas Maebe Note Added: 0039240
2010-11-26 13:57 Jonas Maebe Status resolved => closed