[PATCH] D59473: [ValueTracking] Avoid redundant known bits calculation in computeOverflowForSignedAdd()

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

LGTM



================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:4185-4186
   // If the sign of Add is the same as at least one of the operands, this add
-  // CANNOT overflow. This is particularly useful when the sum is
-  // @llvm.assume'ed non-negative rather than proved so from analyzing its
-  // operands.
+  // CANNOT overflow. Check if there is an assumption about the sign of the
+  // result.
   bool LHSOrRHSKnownNonNegative =
----------------
Let's make this comment include more of the description/discussion from this review, so we have it inline in the code. So add something like:
We already calculated the known bits of each operand and checked for ripple. The only other way to improve on the known bits is from an assumption, so call that directly.


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D59473/new/

https://reviews.llvm.org/D59473