[PATCH] D35192: [ARM] Use ADDCARRY / SUBCARRY

[Roger Ferrer Ibanez via Phabricator via llvm-commits]

rogfer01 updated this revision to Diff 107118.
rogfer01 edited the summary of this revision.
rogfer01 added a comment.

ChangeLog:

- Correctly handle the second operand of `ISD::SUBCARRY`. We need to invert its value (i.e. `1-x`) before passing it to `ARMISD::SUBE`, also the result of `ARMISD::SUBE` has to be inverted again to match what `ISD::SUBCARRY` means.
- Fix `USUBO` lowering as a consequence of the above.
- Add a combiner for `(SUBC 1, (SUBC 1, X)) → X `
- Compute the known bits of `(SUBC 1, (ADDE 0, 0, C))` (1 bit) to avoid spurious `and` instructions.
- Update the tests for `usub_builtin_overflow` with the correct code generation.
- Remove combiners that became pointless after the changes above.


https://reviews.llvm.org/D35192

Files:
  lib/Target/ARM/ARMISelLowering.cpp
  lib/Target/ARM/ARMISelLowering.h
  test/CodeGen/ARM/intrinsics-overflow.ll

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