clang/test/CodeGenCXX/stack-reuse.cpp

   1 // RUN: %clang_cc1 -triple armv7-unknown-linux-gnueabihf %s -o - -emit-llvm -O2 | FileCheck %s
   2
   3 // Stack should be reused when possible, no need to allocate two separate slots
   4 // if they have disjoint lifetime.
   5
   6 // Sizes of objects are related to previously existed threshold of 32.  In case
   7 // of S_large stack size is rounded to 40 bytes.
   8
   9 // 32B
  10 struct S_small {
  11   int a[8];
  12 };
  13
  14 // 36B
  15 struct S_large {
  16   int a[9];
  17 };
  18
  19 // Helper class for lifetime scope absence testing
  20 struct Combiner {
  21   S_large a, b;
  22
  23   Combiner(S_large);
  24   Combiner f();
  25 };
  26
  27 extern S_small foo_small();
  28 extern S_large foo_large();
  29 extern void bar_small(S_small*);
  30 extern void bar_large(S_large*);
  31
  32 // Prevent mangling of function names.
  33 extern "C" {
  34
  35 void small_rvoed_unnamed_temporary_object() {
  36 // CHECK-LABEL: define{{.*}} void @small_rvoed_unnamed_temporary_object
  37 // CHECK: call void @llvm.lifetime.start
  38 // CHECK: call void @_Z9foo_smallv
  39 // CHECK: call void @llvm.lifetime.end
  40 // CHECK: call void @llvm.lifetime.start
  41 // CHECK: call void @_Z9foo_smallv
  42 // CHECK: call void @llvm.lifetime.end
  43
  44   foo_small();
  45   foo_small();
  46 }
  47
  48 void large_rvoed_unnamed_temporary_object() {
  49 // CHECK-LABEL: define{{.*}} void @large_rvoed_unnamed_temporary_object
  50 // CHECK: call void @llvm.lifetime.start
  51 // CHECK: call void @_Z9foo_largev
  52 // CHECK: call void @llvm.lifetime.end
  53 // CHECK: call void @llvm.lifetime.start
  54 // CHECK: call void @_Z9foo_largev
  55 // CHECK: call void @llvm.lifetime.end
  56
  57   foo_large();
  58   foo_large();
  59 }
  60
  61 void small_rvoed_named_temporary_object() {
  62 // CHECK-LABEL: define{{.*}} void @small_rvoed_named_temporary_object
  63 // CHECK: call void @llvm.lifetime.start
  64 // CHECK: call void @_Z9foo_smallv
  65 // CHECK: call void @llvm.lifetime.end
  66 // CHECK: call void @llvm.lifetime.start
  67 // CHECK: call void @_Z9foo_smallv
  68 // CHECK: call void @llvm.lifetime.end
  69
  70   {
  71     S_small s = foo_small();
  72   }
  73   {
  74     S_small s = foo_small();
  75   }
  76 }
  77
  78 void large_rvoed_named_temporary_object() {
  79 // CHECK-LABEL: define{{.*}} void @large_rvoed_named_temporary_object
  80 // CHECK: call void @llvm.lifetime.start
  81 // CHECK: call void @_Z9foo_largev
  82 // CHECK: call void @llvm.lifetime.end
  83 // CHECK: call void @llvm.lifetime.start
  84 // CHECK: call void @_Z9foo_largev
  85 // CHECK: call void @llvm.lifetime.end
  86
  87   {
  88     S_large s = foo_large();
  89   }
  90   {
  91     S_large s = foo_large();
  92   }
  93 }
  94
  95 void small_auto_object() {
  96 // CHECK-LABEL: define{{.*}} void @small_auto_object
  97 // CHECK: call void @llvm.lifetime.start
  98 // CHECK: call void @_Z9bar_smallP7S_small
  99 // CHECK: call void @llvm.lifetime.end
 100 // CHECK: call void @llvm.lifetime.start
 101 // CHECK: call void @_Z9bar_smallP7S_small
 102 // CHECK: call void @llvm.lifetime.end
 103
 104   {
 105     S_small s;
 106     bar_small(&s);
 107   }
 108   {
 109     S_small s;
 110     bar_small(&s);
 111   }
 112 }
 113
 114 void large_auto_object() {
 115 // CHECK-LABEL: define{{.*}} void @large_auto_object
 116 // CHECK: call void @llvm.lifetime.start
 117 // CHECK: call void @_Z9bar_largeP7S_large
 118 // CHECK: call void @llvm.lifetime.end
 119 // CHECK: call void @llvm.lifetime.start
 120 // CHECK: call void @_Z9bar_largeP7S_large
 121 // CHECK: call void @llvm.lifetime.end
 122
 123   {
 124     S_large s;
 125     bar_large(&s);
 126   }
 127   {
 128     S_large s;
 129     bar_large(&s);
 130   }
 131 }
 132
 133 int large_combiner_test(S_large s) {
 134 // CHECK-LABEL: define{{.*}} i32 @large_combiner_test
 135 // CHECK: [[T2:%.*]] = alloca %struct.Combiner
 136 // CHECK: [[T1:%.*]] = alloca %struct.Combiner
 137 // CHECK: [[T3:%.*]] = call noundef ptr @_ZN8CombinerC1E7S_large(ptr {{[^,]*}} [[T1]], [9 x i32] %s.coerce)
 138 // CHECK: call void @_ZN8Combiner1fEv(ptr nonnull sret(%struct.Combiner) align 4 [[T2]], ptr {{[^,]*}} [[T1]])
 139 // CHECK: [[T5:%.*]] = load i32, ptr [[T2]]
 140 // CHECK: ret i32 [[T5]]
 141
 142   return Combiner(s).f().a.a[0];
 143 }
 144
 145 }