Subzero: Allow delaying Phi lowering until after register allocation.

tests_lit/llvm2ice_tests/nacl-atomic-cmpxchg-optimization.ll

 ; This tests the optimization of atomic cmpxchg w/ following cmp + branches.
 
 ; RUN: %p2i -i %s --args -O2 --verbose none \
 ; RUN:   | llvm-mc -triple=i686-none-nacl -x86-asm-syntax=intel -filetype=obj \
 ; RUN:   | llvm-objdump -d -symbolize -x86-asm-syntax=intel - \
 ; RUN:   | FileCheck --check-prefix=O2 %s
 ; RUN: %p2i -i %s --args -Om1 --verbose none \
 ; RUN:   | llvm-mc -triple=i686-none-nacl -x86-asm-syntax=intel -filetype=obj \
 ; RUN:   | llvm-objdump -d -symbolize -x86-asm-syntax=intel - \
 ; RUN:   | FileCheck --check-prefix=OM1 %s
@@ skipping 21 matching lines @@
   %success = icmp eq i32 %expected_loop, %old
   br i1 %success, label %done, label %loop
 
 done:
   call void @use_value(i32 %old)
   ret i32 %succeeded_first_try
 }
 ; O2-LABEL: test_atomic_cmpxchg_loop
 ; O2: lock
 ; O2-NEXT: cmpxchg dword ptr [e{{[^a].}}], e{{[^a]}}
-; O2-NOT: cmp
-; Make sure the phi assignment for succeeded_first_try is still there.
-; O2: mov {{.*}}, 2
-; O2-NOT: cmp
-; O2: jne
+; O2-NEXT: j{{e|ne}}
 ; Make sure the call isn't accidentally deleted.
 ; O2: call
 ;
 ; Check that the unopt version does have a cmp
 ; OM1-LABEL: test_atomic_cmpxchg_loop
 ; OM1: lock
 ; OM1-NEXT: cmpxchg dword ptr [e{{[^a].}}], e{{[^a]}}
 ; OM1: cmp
 ; OM1: je
 ; OM1: call
@@ skipping 33 matching lines @@
                                                 i32 %desired, i32 6, i32 6)
   %success = icmp eq i32 %old, 0
   br i1 %success, label %done, label %loop
 
 done:
   ret i32 %succeeded_first_try
 }
 ; O2-LABEL: test_atomic_cmpxchg_loop_const
 ; O2: lock
 ; O2-NEXT: cmpxchg dword ptr [e{{[^a].}}], e{{[^a]}}
-; O2-NOT: cmp
-; O2: jne
+; O2-NEXT: j{{e|ne}}
 
 ; This is a case where the flags cannot be reused (compare is for some
 ; other condition).
 define i32 @test_atomic_cmpxchg_no_opt(i32 %iptr, i32 %expected, i32 %desired) {
 entry:
   br label %loop
 
 loop:
   %expected_loop = phi i32 [ %expected, %entry ], [ %old, %loop ]
   %ptr = inttoptr i32 %iptr to i32*
   %old = call i32 @llvm.nacl.atomic.cmpxchg.i32(i32* %ptr, i32 %expected_loop,
                                                 i32 %desired, i32 6, i32 6)
   %success = icmp sgt i32 %old, %expected
   br i1 %success, label %done, label %loop
 
 done:
   ret i32 %old
 }
 ; O2-LABEL: test_atomic_cmpxchg_no_opt
 ; O2: lock
 ; O2-NEXT: cmpxchg dword ptr [e{{[^a].}}], e{{[^a]}}
-; O2: mov {{.*}}
 ; O2: cmp
 ; O2: jle
 
 ; Another case where the flags cannot be reused (the comparison result
 ; is used somewhere else).
 define i32 @test_atomic_cmpxchg_no_opt2(i32 %iptr, i32 %expected, i32 %desired) {
 entry:
   br label %loop
 
 loop:
   %expected_loop = phi i32 [ %expected, %entry ], [ %old, %loop ]
   %ptr = inttoptr i32 %iptr to i32*
   %old = call i32 @llvm.nacl.atomic.cmpxchg.i32(i32* %ptr, i32 %expected_loop,
                                                 i32 %desired, i32 6, i32 6)
   %success = icmp eq i32 %old, %expected
   br i1 %success, label %done, label %loop
 
 done:
   %r = zext i1 %success to i32
   ret i32 %r
 }
 ; O2-LABEL: test_atomic_cmpxchg_no_opt2
 ; O2: lock
 ; O2-NEXT: cmpxchg dword ptr [e{{[^a].}}], e{{[^a]}}
 ; O2: mov {{.*}}
 ; O2: cmp
 ; O2: je
 
 ; ERRORS-NOT: ICE translation error