On Oct 21, 2005, at 9:19 AM, Toon Moene wrote:
L.S.,
This code:
SUBROUTINE S(A, B, N)
DIMENSION A(N), B(N)
READ*,Z,B
DO I = 1, N
A(I) = Z * B(I)
ENDDO
PRINT*,A
END
when compiled thusly:
The problem here is not really related to the vectorizer but the
tree aliasing code. The loop looks like this at -O2 in the tree dumps:
# z_49 = PHI <z_86(1), z_124(3)>;
# i_1 = PHI <1(1), i_48(3)>;
<L8>:;
D.982_41 = i_1 + -1;
# VUSE <z_49>;
D.983_43 = (*b_20)[D.982_41];
# VUSE <z_49>;
z.4_45 = z;
D.985_46 = D.983_43 * z.4_45;
# z_124 = V_MAY_DEF <z_49>;
(*a_36)[D.982_41] = D.985_46;
i_48 = i_1 + 1;
if (i_1 == D.972_25) goto <L4>; else goto <L13>;
Notice how the statement which does "A(I) =" has a V_MAY_DEF of z. If
we
recorded it correctly, A and B would aliasing nothing as they are
arguments
passed in.
-- Pinski
