I have discovered a few Inline Assembly bugs in XCode.
I have been porting a Codewarrior application to XCode and have found
ways to workaround minor differences in Inline Assembly, but I am
stuck without a workaround for a few items.
All of the items listed below work in Codewarrior but I can't get
them to work in XCode.
I have provided some simple example code to illustrate these problems
(see bottom).
1.) Non-volatile registers are clobbered in automatically generated
stack frame for PowerPC.
Disassemble the example - functions disassemble1() and disassemble2()
both write to r28 and r29 without first saving them.
2.) The "nofralloc" directive seems to be ignored both in PowerPC and
Intel assembly.
Functions disassemble2() (PowerPC) and foo() (Intel) both have glue
code generated.
3.) Member arrays can't be referenced in assembly code.
Function f1() works in Codewarrior but not in XCode. I found a
workaround for the lwz instruction, but the same workaround does not
work in other instructions such as addi. Function f2() shows the same
problem and shows that the workaround does not work either.
4.) Nested member variables can't be referenced in assembly code.
Function f3() illustrates this. Note that this error seems to be
generated at a later stage in compilation and you won't see this
error until you eliminate all other errors.
5.) Intel register bp (ebp) can't be used at all.
Function foo2() shows this.
Does anyone know how to deal with these issues?
Thanks in advance,
Mark
--------------
Here is some sample code that shows these problems.
To use in XCode, create a new Carbon Application project, remove
main.c and add main.cpp with the following contents.
Select Release as the Active Build Configuration to eliminate debug
information shown in disassembled code. Edit the Active Target and
set the Architectures setting to be "ppc" or "i386" depending on
which processor you want to compile for. Comment out all functions
except the one that you want to test.
Select Show Assembly Code from the menu to disassemble the file.
struct A
{
int m1;
};
struct B
{
A m2[10];
};
struct C
{
A m3;
};
struct D
{
C m4;
};
#if defined(__ppc__)
asm void f1()
{
// works in Codewarrior, error in XCode
lwz r3, B.m2[5](r3)
// here is a workaround
lwz r3, B.m2[0] + 5 * sizeof(A)(r3)
}
asm void f2()
{
// works in Codewarrior, error in XCode
addi r3, r3, B.m2[5]
// this does not work either
addi r3, r3, B.m2[0] + 5 * sizeof(A)
}
asm void f3()
{
lwz r3, D.m4.m3(r3)
}
asm int disassemble1(register int a, register int b, register int c,
register int d, register int e, register int f)
{
add r4, a, b
add r6, r5, c
add r7, r6, d
add r8, r7, e
add r3, r8, f
}
asm int disassemble2(register int a, register int b, register int c,
register int d, register int e, register int f)
{
nofralloc
add r4, a, b
add r6, r5, c
add r7, r6, d
add r8, r7, e
add r3, r8, f
bl
}
#endif
#if defined(__i386__)
asm void foo(int a, int b, int c)
{
nofralloc
mov esi, a
add esi, b
add esi, c
ret (3 * 4)
}
// error: bp cannot be used in asm here
asm void foo2(register int a, register int b, register int c)
{
// no automatic stack frame allocation, we will do this manually
nofralloc
// save registers
push ebp
mov ebp, esp
push esi
push edi
// do something here
// ...
// restore registers
pop edi
pop esi
pop ebp
ret (3 * 4)
}
#endif
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Xcode-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/xcode-users/email@hidden
