[llvm] Calculate KnownBits from Metadata correctly for vector loads (PR #128908)

[via llvm-commits]

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@@ -429,10 +429,14 @@ void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
     ConstantInt *Upper =
         mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 1));
     ConstantRange Range(Lower->getValue(), Upper->getValue());
+    unsigned RangeBitWidth = Lower->getBitWidth();
 
     // The first CommonPrefixBits of all values in Range are equal.
     unsigned CommonPrefixBits =
         (Range.getUnsignedMax() ^ Range.getUnsignedMin()).countl_zero();
+    // BitWidth must equal RangeBitWidth.  Otherwise Mask will be set
+    // incorrectly.
+    assert(BitWidth == RangeBitWidth && "BitWidth must equal RangeBitWidth");
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LU-JOHN wrote:

Undo ValueTracking.cpp.  Will be done in separate PR.

https://github.com/llvm/llvm-project/pull/128908