[llvm] Ensure KnownBits passed when calculating from range md has right size (PR #132985)

[Matt Arsenault via llvm-commits]

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@@ -433,6 +433,10 @@ void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
     // The first CommonPrefixBits of all values in Range are equal.
     unsigned CommonPrefixBits =
         (Range.getUnsignedMax() ^ Range.getUnsignedMin()).countl_zero();
+    // BitWidth must equal the Ranges BitWidth for the correct number of high
+    // bits to be set.
+    assert(BitWidth == Lower->getBitWidth() &&
+           "Known bit width must match range bit width!");
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arsenm wrote:

Move this up and query from Range.getBitWidth()?

https://github.com/llvm/llvm-project/pull/132985