On 12/04/14 13:49, Segher Boessenkool wrote:
On Thu, Dec 04, 2014 at 04:43:34PM +0800, Zhenqiang Chen wrote:
C code:
if (!--*p)
rtl code:
6: r91:SI=[r90:SI]
7: {r88:SI=r91:SI-0x1;clobber flags:CC;}
8: [r90:SI]=r88:SI
9: flags:CCZ=cmp(r88:SI,0)
expected output:
8: {flags:CCZ=cmp([r90:SI]-0x1,0);[r90:SI]=[r90:SI]-0x1;}
in assemble, it is
decl (%eax)
Combine does not consider combining 9 into 7 because there is no LOG_LINK
between them (the link for r88 is between 8 and 7 already).
OK, yea, that's a long standing design decision. We don't feed a single
def into multiple use sites.
jeff
