The following passes are updated to preserve the inst-to-block and
def-use analysies:
private-to-local
aggressive dead-code elimination
dead branch elimination
local-single-block elimination
local-single-store elimination
reduce load size
compact ids (inst-to-block only)
merge block
dead-insert elimination
ccp
The one execption is that compact ids still kills the def-use manager.
This is because it changes so many ids it is faster to kill and rebuild.
Does everything in
https://github.com/KhronosGroup/SPIRV-Tools/issues/1593 except for the
changes to merge return.
We have already disabled common uniform elimination because it created
sequences of loads an entire uniform object, then we extract just a
single element. This caused problems in some drivers, and is just
generally slow because it loads more memory than needed.
However, there are other way to get into this situation, so I've added
a pass that looks specifically for this pattern and removes it when only
a portion of the load is used.
Fixes#1547.
