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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_neg_gep_load(i32* %x) {
     41  entry:
     42   %c = icmp eq i32* %x, null
     43   br i1 %c, label %is_null, label %not_null, !make.implicit !0
     44 
     45  is_null:
     46   ret i32 42
     47 
     48  not_null:
     49 ; null - 5000 * sizeof(i32) lies outside the null page and hence the
     50 ; load to %t cannot be assumed to be reliably faulting.
     51   %x.gep = getelementptr i32, i32* %x, i32 -5000
     52   %t = load i32, i32* %x.gep
     53   ret i32 %t
     54 }
     55 
     56 define i32 @imp_null_check_load_no_md(i32* %x) {
     57 ; This is fine, except it is missing the !make.implicit metadata.
     58  entry:
     59   %c = icmp eq i32* %x, null
     60   br i1 %c, label %is_null, label %not_null
     61 
     62  is_null:
     63   ret i32 42
     64 
     65  not_null:
     66   %t = load i32, i32* %x
     67   ret i32 %t
     68 }
     69 
     70 define i32 @imp_null_check_no_hoist_over_acquire_load(i32* %x, i32* %y) {
     71 ; We cannot hoist %t1 over %t0 since %t0 is an acquire load
     72  entry:
     73   %c = icmp eq i32* %x, null
     74   br i1 %c, label %is_null, label %not_null, !make.implicit !0
     75 
     76  is_null:
     77   ret i32 42
     78 
     79  not_null:
     80   %t0 = load atomic i32, i32* %y acquire, align 4
     81   %t1 = load i32, i32* %x
     82   %p = add i32 %t0, %t1
     83   ret i32 %p
     84 }
     85 
     86 define i32 @imp_null_check_add_result(i32* %x, i32* %y) {
     87 ; This will codegen to:
     88 ;
     89 ;   movl    (%rsi), %eax
     90 ;   addl    (%rdi), %eax
     91 ;
     92 ; The load instruction we wish to hoist is the addl, but there is a
     93 ; write-after-write hazard preventing that from happening.  We could
     94 ; get fancy here and exploit the commutativity of addition, but right
     95 ; now -implicit-null-checks isn't that smart.
     96 ;
     97 
     98  entry:
     99   %c = icmp eq i32* %x, null
    100   br i1 %c, label %is_null, label %not_null, !make.implicit !0
    101 
    102  is_null:
    103   ret i32 42
    104 
    105  not_null:
    106   %t0 = load i32, i32* %y
    107   %t1 = load i32, i32* %x
    108   %p = add i32 %t0, %t1
    109   ret i32 %p
    110 }
    111 
    112 !0 = !{}
    113