llvm/test/CodeGen/AArch64/shrink-wrap-phi.ll

; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
; RUN: llc -mtriple=arm64-apple-darwin -o - %s | FileCheck %s

; In this example, we have a small loop that searches for a 0 word in a string.
; The exit block clobbers callee saves, so should be a good candidate for
; shrink wrapping. However, we have to look through the underlying objects of
; the phi to see this.
define ptr @shrinkwrapme(ptr %p) {
; CHECK-LABEL: shrinkwrapme:
; CHECK:       ; %bb.0: ; %entry
; CHECK-NEXT:    sub x0, x0, #4
; CHECK-NEXT:  LBB0_1: ; %loop
; CHECK-NEXT:    ; =>This Inner Loop Header: Depth=1
; CHECK-NEXT:    ldr w8, [x0, #4]!
; CHECK-NEXT:    cbnz w8, LBB0_1
; CHECK-NEXT:  ; %bb.2: ; %exit
; CHECK-NEXT:    stp x28, x27, [sp, #-16]! ; 16-byte Folded Spill
; CHECK-NEXT:    .cfi_def_cfa_offset 16
; CHECK-NEXT:    .cfi_offset w27, -8
; CHECK-NEXT:    .cfi_offset w28, -16
; CHECK-NEXT:    ; InlineAsm Start
; CHECK-NEXT:    ; InlineAsm End
; CHECK-NEXT:    ldp x28, x27, [sp], #16 ; 16-byte Folded Reload
; CHECK-NEXT:    ret
entry:
  br label %loop

loop:
  %iv = phi ptr [ %p, %entry ], [ %iv.next, %loop ]
  %iv.next = getelementptr inbounds i32, ptr %iv, i64 1
  %load = load i32, ptr %iv
  %load.zero = icmp eq i32 %load, 0
  br i1 %load.zero, label %exit, label %loop

exit:
  call void asm sideeffect "", "~{x27},~{x28}"()
  ret ptr %iv
}

; This example is similar to the previous but one of the underlying objects of
; the phi is a loaded pointer and therefore not guaranteed to avoid the stack.
define ptr @dontshrinkwrapme(ptr %p) {
; CHECK-LABEL: dontshrinkwrapme:
; CHECK:       ; %bb.0: ; %entry
; CHECK-NEXT:    stp x28, x27, [sp, #-16]! ; 16-byte Folded Spill
; CHECK-NEXT:    .cfi_def_cfa_offset 16
; CHECK-NEXT:    .cfi_offset w27, -8
; CHECK-NEXT:    .cfi_offset w28, -16
; CHECK-NEXT:    ldr x8, [x0]
; CHECK-NEXT:    sub x0, x8, #4
; CHECK-NEXT:  LBB1_1: ; %loop
; CHECK-NEXT:    ; =>This Inner Loop Header: Depth=1
; CHECK-NEXT:    ldr w8, [x0, #4]!
; CHECK-NEXT:    cbnz w8, LBB1_1
; CHECK-NEXT:  ; %bb.2: ; %exit
; CHECK-NEXT:    ; InlineAsm Start
; CHECK-NEXT:    ; InlineAsm End
; CHECK-NEXT:    ldp x28, x27, [sp], #16 ; 16-byte Folded Reload
; CHECK-NEXT:    ret
entry:
  %q = load ptr, ptr %p
  br label %loop

loop:
  %iv = phi ptr [ %q, %entry ], [ %iv.next, %loop ]
  %iv.next = getelementptr inbounds i32, ptr %iv, i64 1
  %load = load i32, ptr %iv
  %load.zero = icmp eq i32 %load, 0
  br i1 %load.zero, label %exit, label %loop

exit:
  call void asm sideeffect "", "~{x27},~{x28}"()
  ret ptr %iv
}