unsigned parity(unsigned x) {
x ^= x >> 16;
x ^= x >> 8;
x ^= x >> 4;
x &= 0xf;
return (0x6996 >> x) & 1;
}
gcc 4.2.0 20060506 produces:
extwl a0,0x2,t2
lda v0,27030
xor t2,a0,t2
zapnot t2,0xf,t1 # redundant zero-extension
srl t1,0x8,t1
xor t1,t2,t1
zapnot t1,0xf,t0 # redundant zero-extension
srl t0,0x4,t0
xor t0,t1,t0
and t0,0xf,t0
sra v0,t0,v0
and v0,0x1,v0
-fsee doesn't change anything here.
--
Summary: zero extension not eliminated
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: falk at debian dot org
GCC build triplet: alphaev68-unknown-linux-gnu
GCC host triplet: alphaev68-unknown-linux-gnu
GCC target triplet: alphaev68-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27469
