[llvm] [ValueTracking] Improve `Bitcast` handling to match SDAG (PR #125935)

[Simon Pilgrim via llvm-commits]

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@@ -1331,10 +1332,31 @@ static void computeKnownBitsFromOperator(const Operator *I,
       for (unsigned i = 0; i != SubScale; ++i) {
         computeKnownBits(I->getOperand(0), SubDemandedElts.shl(i), KnownSrc,
                          Depth + 1, Q);
-        unsigned ShiftElt = Q.DL.isLittleEndian() ? i : SubScale - 1 - i;
+        unsigned ShiftElt = IsLE ? i : SubScale - 1 - i;
         Known.insertBits(KnownSrc, ShiftElt * SubBitWidth);
       }
     }
+
+    if (SubBitWidth % BitWidth == 0) {
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RKSimon wrote:

Comments?

https://github.com/llvm/llvm-project/pull/125935