[llvm] X86: Fix convertToThreeAddress losing subregister indexes (PR #124098)

[Simon Pilgrim via llvm-commits]

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@@ -1189,6 +1192,7 @@ bool X86InstrInfo::classifyLEAReg(MachineInstr &MI, const MachineOperand &Src,
     ImplicitOp.setImplicit();
 
     NewSrc = getX86SubSuperRegister(SrcReg, 64);
+    assert(!SubReg);
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RKSimon wrote:

(style) assert message

https://github.com/llvm/llvm-project/pull/124098