[LLVMdev] Question about the IR code of conditional flow

[胡渐飞]

I used llvm.org/demo to generate IR code from c code.
And I found that: when "return " statement appears several times in
different conditional block, IR code does not genrate one "ret "
instruction for each return statement,
it just put a phi node instruction at the end of the function. Just like
this:
int factorial(int X) {
 if (X <100)
  X*=3;
else
  X += 1;
return X + 3;
}
the IR code genrated would be as follow:

define i32 @factorial(i32 %X) nounwind uwtable readnone {
  %1 = icmp slt i32 %X, 100
  br i1 %1, label %2, label %4

; <label>:2                                       ; preds = %0
  %3 = mul nsw i32 %X, 3
  br label %6

; <label>:4                                       ; preds = %0
  %5 = add nsw i32 %X, 1
  br label %6

; <label>:6                                       ; preds = %4, %2
  %.0 = phi i32 [ %3, %2 ], [ %5, %4 ]
  %7 = add nsw i32 %.0, 3
  ret i32 %7
}
Is there any reason or rull to do like this, to use one phi
instruction and only one ret instruction?
As I am trying to generate llvm IR code for my language, can I put
each each ret at each conditional block like follows?

; <label>:2                                       ; preds = %0
  %3 = mul nsw i32 %X, 3
  ret %3
 ; <label>:4                                       ; preds = %0
  %5 = add nsw i32 %X, 1
  ret %5
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