[llvm] [SimplifyCFG] Use hash map to continue hoisting the common instructions (PR #78615)

[Yingwei Zheng via llvm-commits]

================
@@ -1582,19 +1582,29 @@ hoistLockstepIdenticalDPValues(Instruction *TI, Instruction *I1,
   }
 }
 
+// Hash instructions based on following factors:
+// 1- Instruction Opcode
+// 2- Instruction type
+// 3- Instruction operands
+llvm::hash_code getHash(Instruction *Instr) {
+  std::vector<Value *> operands(Instr->op_begin(), Instr->op_end());
+  return llvm::hash_combine(
+      Instr->getOpcode(), Instr->getType(),
+      hash_combine_range(operands.begin(), operands.end()));
----------------
dtcxzyw wrote:

```suggestion
  return llvm::hash_combine(
      Instr->getOpcode(), Instr->getType(),
      hash_combine_range(Instr->op_begin(), Instr->op_end()));
```
TBH I think it is dangerous to calculate hashes for pointers :(
It will make the optimization result non-deterministic if it depends on the iteration order of the hashmap.


https://github.com/llvm/llvm-project/pull/78615