[PATCH] D66762: DAG: computeNumSignBits for MUL

[Matt Arsenault via Phabricator via llvm-commits]

arsenm marked an inline comment as done.
arsenm added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/SelectionDAG.cpp:3723
+    unsigned SignBitsOp0 = ComputeNumSignBits(Op.getOperand(0), Depth + 1);
+    if (SignBitsOp0 == 1)
+      break;
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lebedev.ri wrote:
> `1` is a magic 'i-dont-know', right? I wonder why it's not `-1`,
> that one you certainly can't ever get normally, unlike `1` (`INT_MIN`)
> (Well, yeah, or `Optional<unsigned>`)
There is always the sign bit itself, so any uses should naturally do the right thing from that.


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https://reviews.llvm.org/D66762