As a pending queue data structure to keep track of instructions whose

As a pending queue data structure to keep track of instructions whose
operands have all issued, but whose results are not yet available.  This
allows us to compile:

int G;
int test(int A, int B, int* P) {
   return (G+A)*(B+1);
}

to:

_test:
        lis r2, ha16(L_G$non_lazy_ptr)
        addi r4, r4, 1
        lwz r2, lo16(L_G$non_lazy_ptr)(r2)
        lwz r2, 0(r2)
        add r2, r2, r3
        mullw r3, r2, r4
        blr

instead of this, which has a stall between the lis/lwz:

_test:
        lis r2, ha16(L_G$non_lazy_ptr)
        lwz r2, lo16(L_G$non_lazy_ptr)(r2)
        addi r4, r4, 1
        lwz r2, 0(r2)
        add r2, r2, r3
        mullw r3, r2, r4
        blr

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26716 91177308-0d34-0410-b5e6-96231b3b80d8