[PATCH] D97124: [KnownBits][RISCV] Improve known bits for srem.

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon accepted this revision.
RKSimon added a comment.
This revision is now accepted and ready to land.

LGTM



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Comment at: llvm/lib/Support/KnownBits.cpp:480
+  // in the left hand side must also exist in the result.
+  Known.Zero.setHighBits(LHS.countMinLeadingZeros());
   return Known;
----------------
craig.topper wrote:
> RKSimon wrote:
> > I don't suppose this lets us make the KnownBitsTest exhaustive srem test more accurate? Most binops we still only checks for common subset bits when we might be able to check for exact equality now.
> I tried equality. It failed for both zeros and ones. We don't infer ones unless all bits of the RHS are known. For zeros we're only calculating an upper bound on the result.
Fair enough, thanks for trying.


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https://reviews.llvm.org/D97124