[llvm] [X86] Merge BT with a matching BTR/BTS/BTC (PR #193612)

[Simon Pilgrim via llvm-commits]

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@@ -165,6 +165,14 @@ let IsStrictFP = true in {
 // X86 bit-test instructions.
 def X86bt      : SDNode<"X86ISD::BT",       SDTX86CmpTest>;
 
+// X86 bit-test-and-modify instructions: res, EFLAGS = op src, bitno.
+// CF is set from the pre-operation bit value; BT on the same operands is
+// therefore redundant after one of these nodes. The atomic (locked) variants
+// live under X86ISD::LBTR/LBTS/LBTC.
+def X86btr_flag : SDNode<"X86ISD::BTR", SDTBinaryArithWithFlags>;
+def X86bts_flag : SDNode<"X86ISD::BTS", SDTBinaryArithWithFlags>;
+def X86btc_flag : SDNode<"X86ISD::BTC", SDTBinaryArithWithFlags>;
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RKSimon wrote:

Drop the _flag postfix?

https://github.com/llvm/llvm-project/pull/193612