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88a2a2e053
Unlike the current CSE pass, global value numbering is capable of detecting
common values even if one does not dominate the other. For instance, in
you have
if (...) {
ssa_1 = ssa_0 + 7;
/* use ssa_1 */
} else {
ssa_2 = ssa_0 + 7;
/* use ssa_2 */
}
Global value numbering doesn't care about dominance relationships so it
figures out that ssa_1 and ssa_2 are the same and converts this to
if (...) {
ssa_1 = ssa_0 + 7;
/* use ssa_1 */
} else {
/* use ssa_1 */
}
Obviously, we just broke SSA form which is bad. Global code motion,
however, will repair this for us by turning this into
ssa_1 = ssa_0 + 7;
if (...) {
/* use ssa_1 */
} else {
/* use ssa_1 */
}
This intended to eventually mostly replace CSE. However, conventional CSE
may still be useful because it's less of a scorched-earth approach and
doesn't require GCM. This makes it a bit more appropriate for use as a
clean-up in a late optimization run.
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
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| getopt | ||
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| hgl | ||
| intel | ||
| loader | ||
| mapi | ||
| mesa | ||
| util | ||
| Makefile.am | ||
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