llvm-6502/test/CodeGen/X86/select_const.ll

; RUN: llc < %s -mtriple=x86_64-apple-darwin10 -mcpu=corei7 | FileCheck %s

define i64 @test1(i64 %x) nounwind {
entry:
  %cmp = icmp eq i64 %x, 2
  %add = add i64 %x, 1
  %retval.0 = select i1 %cmp, i64 2, i64 %add
  ret i64 %retval.0

; CHECK: test1:
; CHECK: leaq 1(%rdi), %rax
; CHECK: cmpq $2, %rdi
; CHECK: cmoveq %rdi, %rax
; CHECK: ret

}
Patch by Shuxin Yang <shuxin.llvm@gmail.com>. Original message: The attached is the fix to radar://11663049. The optimization can be outlined by following rules: (select (x != c), e, c) -> select (x != c), e, x), (select (x == c), c, e) -> select (x == c), x, e) where the <c> is an integer constant. The reason for this change is that : on x86, conditional-move-from-constant needs two instructions; however, conditional-move-from-register need only one instruction. While the LowerSELECT() sounds to be the most convenient place for this optimization, it turns out to be a bad place. The reason is that by replacing the constant <c> with a symbolic value, it obscure some instruction-combining opportunities which would otherwise be very easy to spot. For that reason, I have to postpone the change to last instruction-combining phase. The change passes the test of "make check-all -C <build-root/test" and "make -C project/test-suite/SingleSource". git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165661 91177308-0d34-0410-b5e6-96231b3b80d8 2012-10-10 21:31:55 +00:00			`; RUN: llc < %s -mtriple=x86_64-apple-darwin10 -mcpu=corei7 \| FileCheck %s`

			`define i64 @test1(i64 %x) nounwind {`
			`entry:`
			`%cmp = icmp eq i64 %x, 2`
			`%add = add i64 %x, 1`
			`%retval.0 = select i1 %cmp, i64 2, i64 %add`
			`ret i64 %retval.0`

			`; CHECK: test1:`
			`; CHECK: leaq 1(%rdi), %rax`
			`; CHECK: cmpq $2, %rdi`
			`; CHECK: cmoveq %rdi, %rax`
			`; CHECK: ret`

			`}`