[PATCH] D23824: [ADCE] Add handling of PHI nodes when removing control flow

[David Callahan via llvm-commits]

david2050 added a comment.

This snippet

  int foo(int b, int j, int N) {
    if (b) {
      int i;
      for (i = 0; i < N; i++)
        ;
      j =	0;
    }
    return j;
  }

via

  clang -c -emit-llvm -O0 ...
  opt -sroa -adce -adce-remove-loops -S ... 

generates

  define i32 @foo(i32 %b, i32 %j, i32 %N) #0 {
    %1 = icmp ne i32 %b, 0
    br i1 %1, label %2, label %3
  
  ; <label>:2:                                      ; preds = %0
    br label %3
  
  ; <label>:3:                                      ; preds = %2, %0
    %.0 = phi i32 [ %j, %0 ], [ 0, %2 ]
    ret i32 %.0
  }


https://reviews.llvm.org/D23824