Tobias Grosser ha scritto:

On Sat, 2009-04-04 at 09:43 +0200, Roberto Bagnara wrote:

...

Tobias Grosser wrote:

...

thanks a lot for your work on this. I attached the gdb logs for you.

Hi Tobias,

it looks like GCC is miscompiling something: the equality test on two identical long doubles fails. Can you please send the generated assembly code?

Sure,

here the assembly code for ld2.cc compiled with:

g++ -O0 -g -S ld2.cc

As you see in your ld2.s this is the assembler generated for

if (!convert(0x00000000UL, 0x0000000000000001ULL) == 3.6451995318824746025284059336194198163990508156935633437209804870283716886333977368095607086258272051972473473472035311019669856326220321699735080755898090054838225811779316785692252638056335597566215625659834107289403197935535272685912407999541728110155185383830460547687154224492953058597182682142626220675323554608440680792597537396882263389719028133546642119572938120002167626722920322774336390308456055297955188552992122553211711634876291384629300355138527501603132845785873465668580833490531237051939887039833085878399463225014686024594663765868704564236347102423971946588603575680671344779827642197362928177512955605368457612678466479085174632509237360395127227814159533660963994444034021170534884480219777636044379086876232490341169092945505322835546042550164710485109901552496948203761750727745215979248292641646728293792248343785221488475244616533404531408985349389010799994660849957929408670822251678980926263322841336335372303657106066727110161016969869085455268160934467855758 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042064163364874186561053330385457739601909496028500962085690852302287088948745775235125582819733929612639216561639633693884117634763886259524069015182734130370686433835502829622377291959017885993928766510865998492239942591452592404793843806578034980587190625290073394283162299977568998577121169227586830717074729355744992449784197881713384684717511253038609115892894008066372029204294899198702634159516608889754348273042974513623250526934820015248431712290784679105379131381154586266120249707308995151143019152816139292393293515010498592252745641078468181129383391613089431532051176517163804684622961938824442933704843685300968988127789731782849127985502452460634119184826382616940292452732916467073315946752134281587552738824383579602450640510158889185418011397716197432214050377972856694814558106533200089042159975979759073915120262140200120101347075367742276364775809181675078504851970653263910911714517637512376127394984685100090554800250960159855817693701796567811513065659525901019773 98335185042637681982306448413722177895665290302796223004198526079143104070007874540548221582347389579e-4951L) return 1;

movl $1, 4(%esp) movl $0, 8(%esp) movl $0, (%esp) call _Z7convertjy fldz fucompp fnstsw %ax sahf setne %al setp %dl orl %edx, %eax xorl $1, %eax movzbl %al, %eax pushl %eax fildl (%esp) leal 4(%esp), %esp fldz fucompp fnstsw %ax sahf sete %al setnp %dl andl %edx, %eax testb %al, %al je .L36

The constant seen in source file is the minimun denormalized number (with all its decimals) representable with a long double, but it seems that, despite a typo in the last versione of test program we sent to you, it is seen as zero from your compiler.

As a reference this is the code I obtain here with gcc version 4.3.2 (Ubuntu 4.3.2-1ubuntu12) and the attached (fixed) test program.

movl $1, 4(%esp) movl $0, 8(%esp) movl $0, (%esp) call _Z7convertjy fldt .LC3 fucompp fnstsw %ax sahf sete %al setnp %dl andl %edx, %eax xorl $1, %eax testb %al, %al jne .L4

...

.LC3: .long 1 .long 0 .long 0

Now I guess there is something broken in your version of compiler.

I'd like you send me the output of

g++ -v -fsyntax-only -x c++ /dev/null

and

g++ -E -dM -x c++ /dev/null

I'm also interested in the ld2.s generated from fixed test program with -O0, -O1, -O2 to see if something changes. The presence of fldz in generated assembler is the evidence of the miscompilation.

Then, after sending me these info, I'd ask you to try another gcc version (more recent than 4.3.1) to compile both ld2.cc and ppl build to see if this make a difference in one or both.