[llvm] [AArch64][GlobalISel] Add push_mul_through_s/zext (PR #141551)

[Cullen Rhodes via llvm-commits]

================
@@ -229,6 +229,7 @@ void applyFoldGlobalOffset(MachineInstr &MI, MachineRegisterInfo &MRI,
 }
 
 // Combines vecreduce_add(mul(ext(x), ext(y))) -> vecreduce_add(udot(x, y))
+// Or vecreduce_add(ext(mul(ext(x), ext(y)))) -> vecreduce_add(udot(x, y))
 // Or vecreduce_add(ext(x)) -> vecreduce_add(udot(x, 1))
 // Similar to performVecReduceAddCombine in SelectionDAG
 bool matchExtAddvToUdotAddv(MachineInstr &MI, MachineRegisterInfo &MRI,
----------------
c-rhodes wrote:

Does comment/function name also need updating now this also covers sdot? 
```suggestion
// Combines vecreduce_add(mul(ext(x), ext(y))) -> vecreduce_add([us]dot(x, y))
// Or vecreduce_add(ext(mul(ext(x), ext(y)))) -> vecreduce_add([us]dot(x, y))
// Or vecreduce_add(ext(x)) -> vecreduce_add([us]dot(x, 1))
// Similar to performVecReduceAddCombine in SelectionDAG
bool matchExtAddvToDotAddv(MachineInstr &MI, MachineRegisterInfo &MRI,
```

https://github.com/llvm/llvm-project/pull/141551