[llvm] GlobalISel: Use G_UADDE when narrowing G_UMULH (PR #97194)

[Matt Arsenault via llvm-commits]

================
@@ -5716,6 +5716,7 @@ void LegalizerHelper::multiplyRegisters(SmallVectorImpl<Register> &DstRegs,
                                         ArrayRef<Register> Src1Regs,
                                         ArrayRef<Register> Src2Regs,
                                         LLT NarrowTy) {
+  const LLT S1 = LLT::scalar(1);
----------------
arsenm wrote:

It is a constant 

https://github.com/llvm/llvm-project/pull/97194