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Re: [patch] Predictive commoning, updated


You can also use the omega test: -fcheck-data-deps that should compute the distance vectors using two methods, but that will stress only a part of the data dependence analysis, i.e. not the extraction of the dependence test, but only its resolution. Last time I checked, it bootstrapped gcc, but I haven't tried it yet on the cpu2000.

Bootstrap (c only) without your patch is passing with BOOT_CFLAGS= "-O2 -fcheck-data-deps", but including your patch it stops with the error:

(Number of distance vectors differ: Banerjee has 1, Omega has 2.
Banerjee dist vectors:
Omega dist vectors:
data dependence relation:
(Data Dep:
 inner loop index: 0
 loop nest: (49 )
 distance_vector:   0
 distance_vector:   1
 direction_vector:     =
 direction_vector:     +

For an array accessed twice using a constant access function, i.e.
 A[5] =       (1)
 ... = A[5]   (2)

you will have both a distance of 0, as there is a dependence between (1) and
(2) within the same iteration, and a distance of 1, as there is also a
from (2) to (1) but in the next iteration, so this is at a distance of 1.


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