ae8d62c9c5
The initializer for a static local variable cannot be hot, because it runs at most once per program. That's not quite the same thing as having a low branch probability, but under the assumption that the function is invoked many times, modeling this as a branch probability seems reasonable. For TLS variables, the situation is less clear, since the initialization side of the branch can run multiple times in a program execution, but we still expect initialization to be rare relative to non-initialization uses. It would seem worthwhile to add a PGO counter along this path to make this estimation more accurate in future. For globals with guarded initialization, we don't yet apply any branch weights. Due to our use of COMDATs, the guard will be reached exactly once per DSO, but we have no idea how many DSOs will define the variable. llvm-svn: 309195
127 lines
4.5 KiB
C++
127 lines
4.5 KiB
C++
// RUN: %clang_cc1 -emit-llvm -std=c++1z %s -o - -triple=x86_64-linux-gnu | FileCheck %s
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struct S { S(); ~S(); };
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK-NOT: br
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @global)
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S global;
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// CHECK-LABEL: define {{.*}}global_var_init
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// FIXME: Do we really need thread-safe initialization here? We don't run
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// global ctors on multiple threads. (If we were to do so, we'd need thread-safe
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// init for B<int>::member and B<int>::inline_member too.)
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// CHECK: load atomic i8, i8* bitcast (i64* @_ZGV13inline_global to i8*) acquire,
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1
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// CHECK-NOT: !prof
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @inline_global)
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inline S inline_global;
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK-NOT: br
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @thread_local_global)
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thread_local S thread_local_global;
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK: load i8, i8* bitcast (i64* @_ZGV26thread_local_inline_global to i8*)
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1
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// CHECK-NOT: !prof
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @thread_local_inline_global)
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thread_local inline S thread_local_inline_global;
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struct A {
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static S member;
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static thread_local S thread_local_member;
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK: load atomic i8, i8* bitcast (i64* @_ZGVN1A13inline_memberE to i8*) acquire,
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1
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// CHECK-NOT: !prof
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @_ZN1A13inline_memberE)
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static inline S inline_member;
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK: load i8, i8* bitcast (i64* @_ZGVN1A26thread_local_inline_memberE to i8*)
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1
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// CHECK-NOT: !prof
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @_ZN1A26thread_local_inline_memberE)
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static thread_local inline S thread_local_inline_member;
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};
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// CHECK-LABEL: define void @_Z1fv()
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void f() {
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// CHECK: load atomic i8, i8* bitcast (i64* @_ZGVZ1fvE12static_local to i8*) acquire,
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1 {{.*}}, !prof ![[WEIGHTS_LOCAL:[0-9]*]]
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static S static_local;
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// CHECK: load i8, i8* @_ZGVZ1fvE19static_thread_local,
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1 {{.*}}, !prof ![[WEIGHTS_THREAD_LOCAL:[0-9]*]]
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static thread_local S static_thread_local;
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}
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK-NOT: br
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @_ZN1A6memberE)
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S A::member;
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK-NOT: br
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @_ZN1A19thread_local_memberE)
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thread_local S A::thread_local_member;
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template <typename T> struct B {
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK: load i8, i8* bitcast (i64* @_ZGVN1BIiE6memberE to i8*)
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1
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// CHECK-NOT: !prof
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @_ZN1BIiE6memberE)
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static S member;
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK: load i8, i8* bitcast (i64* @_ZGVN1BIiE13inline_memberE to i8*)
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1
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// CHECK-NOT: !prof
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @_ZN1BIiE13inline_memberE)
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static inline S inline_member;
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK: load i8, i8* bitcast (i64* @_ZGVN1BIiE19thread_local_memberE to i8*)
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1
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// CHECK-NOT: !prof
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @_ZN1BIiE19thread_local_memberE)
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static thread_local S thread_local_member;
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// CHECK-LABEL: define {{.*}}global_var_init
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// CHECK: load i8, i8* bitcast (i64* @_ZGVN1BIiE26thread_local_inline_memberE to i8*)
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1
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// CHECK-NOT: !prof
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// CHECK: call void @_ZN1SC1Ev({{.*}}* @_ZN1BIiE26thread_local_inline_memberE)
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static thread_local inline S thread_local_inline_member;
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};
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template<typename T> S B<T>::member;
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template<typename T> thread_local S B<T>::thread_local_member;
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template<typename ...T> void use(T &...);
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void use_b() {
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use(B<int>::member, B<int>::inline_member, B<int>::thread_local_member,
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B<int>::thread_local_inline_member);
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}
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// CHECK-LABEL: define {{.*}}tls_init()
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// CHECK: load i8, i8* @__tls_guard, align 1
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// CHECK: icmp eq i8 {{.*}}, 0
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// CHECK: br i1 {{.*}}, !prof ![[WEIGHTS_THREAD_LOCAL]]
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// CHECK-DAG: ![[WEIGHTS_THREAD_LOCAL]] = !{!"branch_weights", i32 1, i32 1023}
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// CHECK-DAG: ![[WEIGHTS_LOCAL]] = !{!"branch_weights", i32 1, i32 1048575}
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