1. Refactored handling of integer immediate values for add, or, xor and sub.

  New routine: ISel::SelectIntImmediateExpr
  2. Now checking use counts of large constants.  If use count is > 2 then drop
  thru so that the constant gets loaded into a register.
  Source:

int %test1(int %a) {
entry:
       %tmp.1 = add int %a,      123456789      ; <int> [#uses=1]
       %tmp.2 = or  int %tmp.1,  123456789      ; <int> [#uses=1]
       %tmp.3 = xor int %tmp.2,  123456789      ; <int> [#uses=1]
       %tmp.4 = sub int %tmp.3, -123456789      ; <int> [#uses=1]
       ret int %tmp.4
}

Did Emit:

       .machine ppc970


       .text
       .align  2
       .globl  _test1
_test1:
.LBB_test1_0:   ; entry
       addi r2, r3, -13035
       addis r2, r2, 1884
       ori r2, r2, 52501
       oris r2, r2, 1883
       xori r2, r2, 52501
       xoris r2, r2, 1883
       addi r2, r2, 52501
       addis r3, r2, 1883
       blr


Now Emits:

       .machine ppc970


       .text
       .align  2
       .globl  _test1
_test1:
.LBB_test1_0:   ; entry
       lis r2, 1883
       ori r2, r2, 52501
       add r3, r3, r2
       or r3, r3, r2
       xor r3, r3, r2
       add r3, r3, r2
       blr

Patch by Jim Laskey!

llvm-svn: 22749