[llvm] [GlobalISel] Add computeNumSignBits for ASHR (PR #139503)

[David Green via llvm-commits]

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@@ -960,6 +968,64 @@ unsigned GISelValueTracking::computeNumSignBits(Register R, unsigned Depth) {
   return computeNumSignBits(R, DemandedElts, Depth);
 }
 
+std::optional<ConstantRange> GISelValueTracking::getValidShiftAmountRange(
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davemgreen wrote:

What do you mean? The intent was to have it behave the same as the SDAG version, so that it can be reused in similar ways. The IR version seems to only match a single APInt?

https://github.com/llvm/llvm-project/pull/139503