Unconditional branch opcodes (OpCode.Br, OpCode.Br_S) can lead to unverifiable code in the following cases: # DEAD CODE CASE ldc_i4 1 # Stack depth == 1 br Label2 Label1: nop # Dead code, so IL rules assume stack depth == 0. This causes a verification error, # since next instruction has depth == 1 Label2: pop # Stack depth == 1 ret # LATE BRANCH CASE ldc_i4 1 # Stack depth == 1 br Label2 Label1: nop # Not dead code, but since branch comes from below, IL rules assume stack depth = 0. # This causes a verification error, since next instruction has depth == 1 Label2: pop # Stack depth == 1 ret Label3: br Label1 # Stack depth == 1 This method works around the above limitations by using Brtrue or Brfalse in the following way: ldc_i4 1 # Since this test is always true, this is a way of creating a path to the code that brtrue Label # follows the brtrue instruction. ldc_i4 1 # Since this test is always false, this is a way of creating a path to the code that brfalse Label # starts at Label. 1. If opcode == Brtrue or Brtrue_S, then 1 will be pushed and brtrue instruction will be generated. 2. If opcode == Brfalse or Brfalse_S, then 1 will be pushed and brfalse instruction will be generated. 3. If opcode == Br or Br_S, then a br instruction will be generated.
