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      1 ; RUN: llc -mtriple=x86_64-apple-macosx -O3 -debug-only=faultmaps -enable-implicit-null-checks < %s 2>&1 | FileCheck %s
      2 ; REQUIRES: asserts
      3 
      4 ; List cases where we should *not* be emitting implicit null checks.
      5 
      6 ; CHECK-NOT: Fault Map Output
      7 
      8 define i32 @imp_null_check_load(i32* %x, i32* %y) {
      9  entry:
     10   %c = icmp eq i32* %x, null
     11 ; It isn't legal to move the load from %x from "not_null" to here --
     12 ; the store to %y could be aliasing it.
     13   br i1 %c, label %is_null, label %not_null, !make.implicit !0
     14 
     15  is_null:
     16   ret i32 42
     17 
     18  not_null:
     19   store i32 0, i32* %y
     20   %t = load i32, i32* %x
     21   ret i32 %t
     22 }
     23 
     24 define i32 @imp_null_check_gep_load(i32* %x) {
     25  entry:
     26   %c = icmp eq i32* %x, null
     27   br i1 %c, label %is_null, label %not_null, !make.implicit !0
     28 
     29  is_null:
     30   ret i32 42
     31 
     32  not_null:
     33 ; null + 5000 * sizeof(i32) lies outside the null page and hence the
     34 ; load to %t cannot be assumed to be reliably faulting.
     35   %x.gep = getelementptr i32, i32* %x, i32 5000
     36   %t = load i32, i32* %x.gep
     37   ret i32 %t
     38 }
     39 
     40 define i32 @imp_null_check_load_no_md(i32* %x) {
     41 ; This is fine, except it is missing the !make.implicit metadata.
     42  entry:
     43   %c = icmp eq i32* %x, null
     44   br i1 %c, label %is_null, label %not_null
     45 
     46  is_null:
     47   ret i32 42
     48 
     49  not_null:
     50   %t = load i32, i32* %x
     51   ret i32 %t
     52 }
     53 
     54 define i32 @imp_null_check_no_hoist_over_acquire_load(i32* %x, i32* %y) {
     55 ; We cannot hoist %t1 over %t0 since %t0 is an acquire load
     56  entry:
     57   %c = icmp eq i32* %x, null
     58   br i1 %c, label %is_null, label %not_null, !make.implicit !0
     59 
     60  is_null:
     61   ret i32 42
     62 
     63  not_null:
     64   %t0 = load atomic i32, i32* %y acquire, align 4
     65   %t1 = load i32, i32* %x
     66   %p = add i32 %t0, %t1
     67   ret i32 %p
     68 }
     69 
     70 define i32 @imp_null_check_add_result(i32* %x, i32* %y) {
     71 ; This will codegen to:
     72 ;
     73 ;   movl    (%rsi), %eax
     74 ;   addl    (%rdi), %eax
     75 ;
     76 ; The load instruction we wish to hoist is the addl, but there is a
     77 ; write-after-write hazard preventing that from happening.  We could
     78 ; get fancy here and exploit the commutativity of addition, but right
     79 ; now -implicit-null-checks isn't that smart.
     80 ;
     81 
     82  entry:
     83   %c = icmp eq i32* %x, null
     84   br i1 %c, label %is_null, label %not_null, !make.implicit !0
     85 
     86  is_null:
     87   ret i32 42
     88 
     89  not_null:
     90   %t0 = load i32, i32* %y
     91   %t1 = load i32, i32* %x
     92   %p = add i32 %t0, %t1
     93   ret i32 %p
     94 }
     95 
     96 !0 = !{}
     97