swift234

Simplify enum and Int1 integer_literal instructions.

In cases like the one below, replace the integer_literal instructions
with the condition branching to the block that the instruction is in.

    cond_br %10, bb1, bb3

  bb1:
    %13 = integer_literal $Builtin.Int1, -1
    br bb2(%13 : $Builtin.Int1)

  bb3:
    %18 = integer_literal $Builtin.Int1, 0
    br bb2(%18 : $Builtin.Int1)

Similarly, for
    switch_enum %0 : $Bool, case #Bool.true!enumelt: bb1
  bb1:
    %1 = enum $Bool, #Bool.true!enumelt

  we'll replace the enum with %0.

Use this functionality from within the CFG simplification pass to
simplify basic block args in an attempt to expose opportunities for
further CFG simplification.

Swift SVN r9968