Re: Lilypond miscompiled on Fedora 17

[Pavel Roskin]

Quoting David Kastrup <address@hidden>:

> The optimizer does not appear interested in the result of the comparison
> when calculating the minimum value!  There is no conditional path
> entered.  That does not make all too much sense.

That's a truly sharp eye!

A diff between the i386 assembly without -fno-tree-vrp and with  
-fno-tree-vrp has following telltale lines:

 <----->call<-->address@hidden<>#
-.LVL11:
-.LBE73:
+.LVL9:
 .LBE72:
 .LBE71:
+<----->testl<->%eax, %eax<----># D.35568
+<----->movl<-->%esi, %eax<----># <retval>, D.35564
+<----->cmovns<>%edi, %eax<----># tmp88,, D.35564

cmovns is "conditional move if not sign", exactly what we want.  There  
is no similar code in the plain -O2 version.

--
Regards,
Pavel Roskin