Re: [Xenomai-core] Problem with gcc-4.5.1

[Anders Blomdell <anders.blomdell@domain.hid>]

On 2010-12-07 21.21, Gilles Chanteperdrix wrote:
> Anders Blomdell wrote:
>> On 12/07/2010 01:09 PM, Gilles Chanteperdrix wrote:
>>  > Anders Blomdell wrote:
>>  >> On 12/07/2010 12:51 PM, Gilles Chanteperdrix wrote:
>>  >>> Anders Blomdell wrote:
>>  >>>> When compiling Xenomai on Fedora-14 with gcc-4.5.1 [version 4.5.1
>>  >>>> 20100924 (Red Hat 4.5.1-4)], the loading of xeno_nucleus fails 
>> with the
>>  >>>> attached kernel OOPS, a notable difference between the 4.5.1 compiled
>>  >>>> version and a working one built with gcc-4.4.4 on the same system with
>>  >>>> the same configuration, sis tthat __rthal_x86_nodiv_ullimd is not
>>  >>>> inlined, is this anybody has seen before?
>>  >>> No, that is new, we need to see the disassembly of 
>> __rthal_x86_nodiv_ullimd
>>  >>
>>  >> objdump -S:
>>  >>
>>  >> static inline __attribute__((const)) unsigned long long
>>  >> __rthal_x86_nodiv_ullimd(const unsigned long long op,
>>  >> 			 const unsigned long long frac,
>>  >> 			 unsigned integ)
>>  >> {
>>  >>       e7a8:	55                   	push   %ebp
>>  >>       e7a9:	89 e5                	mov    %esp,%ebp
>>  >>       e7ab:	57                   	push   %edi
>>  >>       e7ac:	56                   	push   %esi
>>  >>       e7ad:	53                   	push   %ebx
>>  >>       e7ae:	83 ec 10             	sub    $0x10,%esp
>>  >>       e7b1:	8d 7d 08             	lea    0x8(%ebp),%edi
>>  >>       e7b4:	e8 fc ff ff ff       	call 
>> e7b5<__rthal_x86_nodiv_ullimd+0xd>
>>  >>       e7b9:	8b 1f                	mov    (%edi),%ebx
>>  >>       e7bb:	8b 4f 04             	mov    0x4(%edi),%ecx
>>  >> 	register unsigned rm __asm__("esi");
>>  >> 	register unsigned rh __asm__("edi");
>>  >> 	unsigned fracl, frach, opl, oph;
>>  >> 	register unsigned long long t;
>>  >>
>>  >> 	__rthal_u64tou32(op, oph, opl);
>>  >>       e7be:	89 45 e8             	mov    %eax,-0x18(%ebp)
>>  >> 	__rthal_u64tou32(frac, frach, fracl);
>>  >>       e7c1:	89 5d f0             	mov    %ebx,-0x10(%ebp)
>>  >> 	register unsigned rm __asm__("esi");
>>  >> 	register unsigned rh __asm__("edi");
>>  >> 	unsigned fracl, frach, opl, oph;
>>  >> 	register unsigned long long t;
>>  >>
>>  >> 	__rthal_u64tou32(op, oph, opl);
>>  >>       e7c4:	89 55 e4             	mov    %edx,-0x1c(%ebp)
>>  >> 	__rthal_u64tou32(frac, frach, fracl);
>>  >>       e7c7:	89 4d ec             	mov    %ecx,-0x14(%ebp)
>>  >>
>>  >> 	__asm__ ("mov %[oph], %%eax\n\t"
>>  >>       e7ca:	8b 45 e4             	mov    -0x1c(%ebp),%eax
>>  >>       e7cd:	f7 65 ec             	mull   -0x14(%ebp)
>>  >>       e7d0:	89 c6                	mov    %eax,%esi
>>  >>       e7d2:	89 d7                	mov    %edx,%edi
>>  >>       e7d4:	8b 45 e8             	mov    -0x18(%ebp),%eax
>>  >>       e7d7:	f7 65 f0             	mull   -0x10(%ebp)
>>  >>       e7da:	89 d1                	mov    %edx,%ecx
>>  >>       e7dc:	d1 e0                	shl    %eax
>>  >>       e7de:	83 d1 00             	adc    $0x0,%ecx
>>  >>       e7e1:	83 d6 00             	adc    $0x0,%esi
>>  >>       e7e4:	83 d7 00             	adc    $0x0,%edi
>>  >>       e7e7:	8b 45 e4             	mov    -0x1c(%ebp),%eax
>>  >>       e7ea:	f7 65 f0             	mull   -0x10(%ebp)
>>  >>       e7ed:	01 c1                	add    %eax,%ecx
>>  >>       e7ef:	11 d6                	adc    %edx,%esi
>>  >>       e7f1:	83 d7 00             	adc    $0x0,%edi
>>  >>       e7f4:	8b 45 e8             	mov    -0x18(%ebp),%eax
>>  >>       e7f7:	f7 65 ec             	mull   -0x14(%ebp)
>>  >>       e7fa:	01 c1                	add    %eax,%ecx
>>  >>       e7fc:	11 d6                	adc    %edx,%esi
>>  >>       e7fe:	83 d7 00             	adc    $0x0,%edi
>>  >>       e801:	8b 45 e8             	mov    -0x18(%ebp),%eax
>>  >>       e804:	f7 67 08             	mull   0x8(%edi)
>>  >
>>  > Problem is here: edi is used by gcc as if it contained an address
>>  > whereas it is used by the assembly for the computation. Should be marked
>>  > "early clobber". So,
>>  >
>>  > in include/asm-x86/arith_32.h, replace:
>>  >
>>  > : [rl]"=c"(rl), [rm]"=S"(rm), [rh]"=D"(rh), "=A"(t)
>>  >
>>  > with:
>>  >
>>  > : [rl]"=&c"(rl), [rm]"=&S"(rm), [rh]"=&D"(rh), "=&A"(t)
>>  >
>>  >
>>
>> No cigar (:-()
> 
> Ok. Maybe we can try something less radical, such as:
> 
> : [rl]"=c"(rl), [rm]"=S"(rm), [rh]"=&D"(rh), "=A"(t)
> 
> This is incorrect, but we can hope for the best...
As previously said, changing the optimization from -Os to anything else for
xeno_nucleus (see patch in mail dated 'Tue, 07 Dec 2010 17:20:37 +0100'), solved
that issue (incorrect code + hope for the best -> spurious disasters). Rather
compile time errors than runtime errors.

/Anders

-- 
Anders Blomdell                  Email: anders.blomdell@domain.hid
Department of Automatic Control
Lund University                  Phone:    +46 46 222 4625
P.O. Box 118                     Fax:      +46 46 138118
SE-221 00 Lund, Sweden