[PATCH] D51112: [ValueTracking] Teach computeNumSignBits to understand min/max clamp patterns with constant/splat values

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

> I'm not entirely sure if we can assume the constant is canonicalized to the RHS.

Instcombine does this in canonicalizeMinMaxWithConstant if the compare has one use.  Probably good enough.

> Should the depth limit be bumped by 2 since we went through 2 nodes?

Bumping by 1 should be fine given the pattern-matching is cheap; the point of the depth limit is just to prevent non-linear compile-time, anyway.

----

Can you factor out the clamp matching into a separate helper?



================
Comment at: lib/Analysis/ValueTracking.cpp:2385
+
+        if (CLow->sle(*CHigh)) {
+          Tmp = ComputeNumSignBits(LHS2, Depth + 1, Q);
----------------
CLow and CHigh have to be constants so you can perform this "sle" check?


https://reviews.llvm.org/D51112