Substantially improve the code generated by non-folded setcc instructions.

Substantially improve the code generated by non-folded setcc instructions.
In particular, instead of compiling this:

bool %test(int %A, int %B) {
  %C = setlt int %A, %B
  ret bool %C
}

to this:

test:
        save %sp, -96, %sp
        subcc %i0, %i1, %g0
        bl .LBBtest_1   !
        nop
        ba .LBBtest_2   !
        nop
.LBBtest_1:     !
        or %g0, 1, %i0
        ba .LBBtest_3   !
        nop
.LBBtest_2:     !
        or %g0, 0, %i0
        ba .LBBtest_3   !
        nop
.LBBtest_3:     !
        restore %g0, %g0, %g0
        retl
        nop

We now compile it to this:

test:
        save %sp, -96, %sp
        subcc %i0, %i1, %g0
        or %g0, 1, %i0
        bl .LBBtest_2   !
        nop
.LBBtest_1:     !
        or %g0, %g0, %i0
.LBBtest_2:     !
        restore %g0, %g0, %g0
        retl
        nop

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19213 91177308-0d34-0410-b5e6-96231b3b80d8