llvm dev - Jul 2010 - [LLVMdev] Win32 COFF Support patch 5 (the final patch in the saga!)

Daniel somehow replied to one of my previous commits on llvm-commits
instead of this thread.

On Mon, Jul 26, 2010 at 12:41 AM, Daniel Dunbar <daniel at zuster.org>
wrote:
> Hi Michael,
>
> Two minor notes:
> --
>> diff --git a/lib/Target/X86/X86AsmBackend.cpp
b/lib/Target/X86/X86AsmBackend.cpp
>> index 2cf65c1..02ac2be 100644
>> --- a/lib/Target/X86/X86AsmBackend.cpp
>> +++ b/lib/Target/X86/X86AsmBackend.cpp
>> @@ -14,6 +14,7 @@
>>  #include "llvm/MC/MCAssembler.h"
>>  #include "llvm/MC/MCExpr.h"
>>  #include "llvm/MC/MCObjectWriter.h"
>> +#include "llvm/MC/MCSectionCOFF.h"
>>  #include "llvm/MC/MCSectionELF.h"
>>  #include "llvm/MC/MCSectionMachO.h"
>>  #include "llvm/MC/MachObjectWriter.h"
>> @@ -212,6 +213,24 @@ public:
>>      : ELFX86AsmBackend(T) {}
>>  };
>>
>> +class WindowsX86AsmBackend : public X86AsmBackend {
>> +public:
>> +  WindowsX86AsmBackend(const Target &T)
>> +    : X86AsmBackend(T) {
>> +    HasAbsolutizedSet = true;
>> +    HasScatteredSymbols = true;
>
> These probably should be false for Win32.
What do they do?
>> diff --git a/test/MC/COFF/dg.exp b/test/MC/COFF/dg.exp
>> new file mode 100644
>> index 0000000..7b7bd4e
>> --- /dev/null
>> +++ b/test/MC/COFF/dg.exp
>> @@ -0,0 +1,5 @@
>> +load_lib llvm.exp
>> +
>> +if { [llvm_supports_target X86] } {
>> +  RunLLVMTests [lsort [glob -nocomplain $srcdir/$subdir/*.{ll}]]
>> +}
>
> This should be *.{s}.
This has to be *.{ll} for now because llvm-mc cannot parse COFF .s files.
> --
>
> Otherwise looks good to me!
>
>  - Daniel
- Michael Spencer

Michael,

Thanks for taking the time to get this into the mainline.

 - Nathan

On Mon, Jul 26, 2010 at 7:25 PM, Michael Spencer <bigcheesegs at
gmail.com>wrote:
> Daniel somehow replied to one of my previous commits on llvm-commits
> instead of this thread.
>
> On Mon, Jul 26, 2010 at 12:41 AM, Daniel Dunbar <daniel at
zuster.org> wrote:
> > Hi Michael,
> >
> > Two minor notes:
> > --
> >> diff --git a/lib/Target/X86/X86AsmBackend.cpp
> b/lib/Target/X86/X86AsmBackend.cpp
> >> index 2cf65c1..02ac2be 100644
> >> --- a/lib/Target/X86/X86AsmBackend.cpp
> >> +++ b/lib/Target/X86/X86AsmBackend.cpp
> >> @@ -14,6 +14,7 @@
> >>  #include "llvm/MC/MCAssembler.h"
> >>  #include "llvm/MC/MCExpr.h"
> >>  #include "llvm/MC/MCObjectWriter.h"
> >> +#include "llvm/MC/MCSectionCOFF.h"
> >>  #include "llvm/MC/MCSectionELF.h"
> >>  #include "llvm/MC/MCSectionMachO.h"
> >>  #include "llvm/MC/MachObjectWriter.h"
> >> @@ -212,6 +213,24 @@ public:
> >>      : ELFX86AsmBackend(T) {}
> >>  };
> >>
> >> +class WindowsX86AsmBackend : public X86AsmBackend {
> >> +public:
> >> +  WindowsX86AsmBackend(const Target &T)
> >> +    : X86AsmBackend(T) {
> >> +    HasAbsolutizedSet = true;
> >> +    HasScatteredSymbols = true;
> >
> > These probably should be false for Win32.
>
> What do they do?
>
> >> diff --git a/test/MC/COFF/dg.exp b/test/MC/COFF/dg.exp
> >> new file mode 100644
> >> index 0000000..7b7bd4e
> >> --- /dev/null
> >> +++ b/test/MC/COFF/dg.exp
> >> @@ -0,0 +1,5 @@
> >> +load_lib llvm.exp
> >> +
> >> +if { [llvm_supports_target X86] } {
> >> +  RunLLVMTests [lsort [glob -nocomplain $srcdir/$subdir/*.{ll}]]
> >> +}
> >
> > This should be *.{s}.
>
> This has to be *.{ll} for now because llvm-mc cannot parse COFF .s files.
>
> > --
> >
> > Otherwise looks good to me!
> >
> >  - Daniel
>
> - Michael Spencer
>
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On Mon, Jul 26, 2010 at 7:25 PM, Michael Spencer <bigcheesegs at
gmail.com> wrote:
> Daniel somehow replied to one of my previous commits on llvm-commits
> instead of this thread.
>
> On Mon, Jul 26, 2010 at 12:41 AM, Daniel Dunbar <daniel at
zuster.org> wrote:
>> Hi Michael,
>>
>> Two minor notes:
>> --
>>> diff --git a/lib/Target/X86/X86AsmBackend.cpp
b/lib/Target/X86/X86AsmBackend.cpp
>>> index 2cf65c1..02ac2be 100644
>>> --- a/lib/Target/X86/X86AsmBackend.cpp
>>> +++ b/lib/Target/X86/X86AsmBackend.cpp
>>> @@ -14,6 +14,7 @@
>>>  #include "llvm/MC/MCAssembler.h"
>>>  #include "llvm/MC/MCExpr.h"
>>>  #include "llvm/MC/MCObjectWriter.h"
>>> +#include "llvm/MC/MCSectionCOFF.h"
>>>  #include "llvm/MC/MCSectionELF.h"
>>>  #include "llvm/MC/MCSectionMachO.h"
>>>  #include "llvm/MC/MachObjectWriter.h"
>>> @@ -212,6 +213,24 @@ public:
>>>      : ELFX86AsmBackend(T) {}
>>>  };
>>>
>>> +class WindowsX86AsmBackend : public X86AsmBackend {
>>> +public:
>>> +  WindowsX86AsmBackend(const Target &T)
>>> +    : X86AsmBackend(T) {
>>> +    HasAbsolutizedSet = true;
>>> +    HasScatteredSymbols = true;
>>
>> These probably should be false for Win32.
>
> What do they do?
You don't really want to know, but:
(1) The Darwin tools conspire to allow the linker to reorder code, do
dead code stripping, etc. What this means is that any two "atoms" in
an assembly file might be moved in the final linked image. Therefore,
you can't expect that things like 'A - B' are constants.

(2) "Absolutized set" is something where Darwin 'as' will take
a
directive like '.set foo, A - B', and make foo be the current absolute
expression for A - B, ignoring the fact that A and B might move. In
practice, this is because the assembler wasn't smart enough to figure
out which situations it could reliably compute A - B. This is related
to (1).

These two things end up impacting relaxation and the assembler
backend, which is why they unfortunately get exposed at this level.
>>> diff --git a/test/MC/COFF/dg.exp b/test/MC/COFF/dg.exp
>>> new file mode 100644
>>> index 0000000..7b7bd4e
>>> --- /dev/null
>>> +++ b/test/MC/COFF/dg.exp
>>> @@ -0,0 +1,5 @@
>>> +load_lib llvm.exp
>>> +
>>> +if { [llvm_supports_target X86] } {
>>> +  RunLLVMTests [lsort [glob -nocomplain $srcdir/$subdir/*.{ll}]]
>>> +}
>>
>> This should be *.{s}.
>
> This has to be *.{ll} for now because llvm-mc cannot parse COFF .s files.
Oh, right.

 - Daniel
>
>> --
>>
>> Otherwise looks good to me!
>>
>>  - Daniel
>
> - Michael Spencer
>

On Fri, Jul 30, 2010 at 1:28 PM, Daniel Dunbar <daniel at zuster.org>
wrote:
> On Mon, Jul 26, 2010 at 7:25 PM, Michael Spencer <bigcheesegs at
gmail.com> wrote:
>> Daniel somehow replied to one of my previous commits on llvm-commits
>> instead of this thread.
>>
>> On Mon, Jul 26, 2010 at 12:41 AM, Daniel Dunbar <daniel at
zuster.org> wrote:
>>> Hi Michael,
>>>
>>> Two minor notes:
>>> --
>>>> diff --git a/lib/Target/X86/X86AsmBackend.cpp
b/lib/Target/X86/X86AsmBackend.cpp
>>>> index 2cf65c1..02ac2be 100644
>>>> --- a/lib/Target/X86/X86AsmBackend.cpp
>>>> +++ b/lib/Target/X86/X86AsmBackend.cpp
>>>> @@ -14,6 +14,7 @@
>>>>  #include "llvm/MC/MCAssembler.h"
>>>>  #include "llvm/MC/MCExpr.h"
>>>>  #include "llvm/MC/MCObjectWriter.h"
>>>> +#include "llvm/MC/MCSectionCOFF.h"
>>>>  #include "llvm/MC/MCSectionELF.h"
>>>>  #include "llvm/MC/MCSectionMachO.h"
>>>>  #include "llvm/MC/MachObjectWriter.h"
>>>> @@ -212,6 +213,24 @@ public:
>>>>      : ELFX86AsmBackend(T) {}
>>>>  };
>>>>
>>>> +class WindowsX86AsmBackend : public X86AsmBackend {
>>>> +public:
>>>> +  WindowsX86AsmBackend(const Target &T)
>>>> +    : X86AsmBackend(T) {
>>>> +    HasAbsolutizedSet = true;
>>>> +    HasScatteredSymbols = true;
>>>
>>> These probably should be false for Win32.
>>
>> What do they do?
>
> You don't really want to know, but:
> (1) The Darwin tools conspire to allow the linker to reorder code, do
> dead code stripping, etc. What this means is that any two "atoms"
in
> an assembly file might be moved in the final linked image. Therefore,
> you can't expect that things like 'A - B' are constants.
>
> (2) "Absolutized set" is something where Darwin 'as' will
take a
> directive like '.set foo, A - B', and make foo be the current
absolute
> expression for A - B, ignoring the fact that A and B might move. In
> practice, this is because the assembler wasn't smart enough to figure
> out which situations it could reliably compute A - B. This is related
> to (1).
>
> These two things end up impacting relaxation and the assembler
> backend, which is why they unfortunately get exposed at this level.
I tried setting these to false, but the resulting executable (made
with link.exe) crashed. I looked at the differences in the object
file, but couldn't figure out what was causing it. I'm guessing
there's a bug in the path when these are false.

Now that I know what these flags do, I'll try and figure out exactly
what the problem is.

- Michael Spencer
>>>> diff --git a/test/MC/COFF/dg.exp b/test/MC/COFF/dg.exp
>>>> new file mode 100644
>>>> index 0000000..7b7bd4e
>>>> --- /dev/null
>>>> +++ b/test/MC/COFF/dg.exp
>>>> @@ -0,0 +1,5 @@
>>>> +load_lib llvm.exp
>>>> +
>>>> +if { [llvm_supports_target X86] } {
>>>> +  RunLLVMTests [lsort [glob -nocomplain
$srcdir/$subdir/*.{ll}]]
>>>> +}
>>>
>>> This should be *.{s}.
>>
>> This has to be *.{ll} for now because llvm-mc cannot parse COFF .s
files.
>
> Oh, right.
>
>  - Daniel
>
>>
>>> --
>>>
>>> Otherwise looks good to me!
>>>
>>>  - Daniel
>>
>> - Michael Spencer
>>
>