Statement, which paves the way to make SSAValue's have a useful owner
available, which will allow subsequent patches to improve their use/def
chains.
While I'm poking at this, shrink sizeof(Instruction) and sizeof(Statement) by a
word by packing the kind and location together into a single PointerIntPair.
NFC.
PiperOrigin-RevId: 218959651
1) We incorrectly reassociated non-reassociative operations like subi, causing
miscompilations.
2) When constant folding, we didn't add users of the new constant back to the
worklist for reprocessing, causing us to miss some cases (pointed out by
Uday).
The code for tensorflow/mlir#2 is gross, but I'll add the new APIs in a followup patch.
PiperOrigin-RevId: 218803984
River Riddle