------- Comment #5 from rguenth at gcc dot gnu dot org 2008-03-15 11:28 -------
Sorry. The tree optimizers produce
<L62>:;
__asm__ __volatile__("fistl %0":"=m" r:"t" txcum * 2.0e+0 - 5.0e-1);
D.16879 = r >> 1;
if (D.16879 < sp->bbox[0]) goto <L105>; else goto <L17>;
<L105>:;
__b = &D.12083;
goto <bb 20> (<L18>);
<L17>:;
__b = &sp->bbox[0];
<L18>:;
sp->bbox[0] = *__b;
which looks suspicious as well, as D.12083 is not the correct result here
(but in fact is uninitialized). And this is store-sinking which makes
a mess of it:
Sinking # D.12083_947 = V_MUST_DEF <D.12083_380>;
D.12083 = D.16879_333 from bb 21 to bb 52
because of wrong alias information computed right before this pass:
<L62>:;
D.16874_329 = txcum_285 * 2.0e+0;
x_330 = D.16874_329 - 5.0e-1;
# r_946 = V_MAY_DEF <r_288>;
__asm__ __volatile__("fistl %0":"=m" r:"t" x_330);
# VUSE <r_946>;
r.41_332 = r;
D.16879_333 = r.41_332 >> 1;
# D.12083_947 = V_MUST_DEF <D.12083_380>;
D.12083 = D.16879_333;
# VUSE <SFT.738_136>;
# VUSE <SFT.739_451>;
# VUSE <SFT.740_367>;
D.16880_340 = sp_119->bbox[0];
if (D.16879_333 < D.16880_340) goto <L91>; else goto <L17>;
<L91>:;
goto <bb 23> (<L18>);
<L17>:;
__b_342 = &sp_119->bbox[0];
# __b_5 = PHI <&D.12083(48), __b_342(22)>;
<L18>:;
# VUSE <r_946>;
# VUSE <r_284>;
# VUSE <r_6>;
# VUSE <r_43>;
D.12120_344 = *__b_5;
Oh well, it's not that 4.2 does not have known aliasing related problems.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |UNCONFIRMED
Component|c++ |tree-optimization
Keywords| |alias, wrong-code
Priority|P3 |P2
Resolution|DUPLICATE |
Summary|Miscompiled inline assembly |[4.2 Regression] Miscompiled
| |inline assembly
Target Milestone|--- |4.2.4
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35585
