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
101 lines
4.4 KiB
C++
101 lines
4.4 KiB
C++
// RUN: %clang_cc1 -fexceptions -fcxx-exceptions -fms-extensions -fms-compatibility -fms-compatibility-version=19 -std=c++11 -emit-llvm %s -o - -triple=i386-pc-win32 | FileCheck %s
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// REQUIRES: asserts
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struct S {
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S();
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~S();
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};
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// CHECK-DAG: @"\01?s@?1??f@@YAAAUS@@XZ@4U2@A" = linkonce_odr thread_local global %struct.S zeroinitializer
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// CHECK-DAG: @"\01??__J?1??f@@YAAAUS@@XZ@51" = linkonce_odr thread_local global i32 0
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// CHECK-DAG: @"\01?s@?1??g@@YAAAUS@@XZ@4U2@A" = linkonce_odr global %struct.S zeroinitializer
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// CHECK-DAG: @"\01?$TSS0@?1??g@@YAAAUS@@XZ@4HA" = linkonce_odr global i32 0
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// CHECK-DAG: @_Init_thread_epoch = external thread_local global i32, align 4
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// CHECK-DAG: @"\01?j@?1??h@@YAAAUS@@_N@Z@4U2@A" = linkonce_odr thread_local global %struct.S zeroinitializer
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// CHECK-DAG: @"\01??__J?1??h@@YAAAUS@@_N@Z@51" = linkonce_odr thread_local global i32 0
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// CHECK-DAG: @"\01?i@?1??h@@YAAAUS@@_N@Z@4U2@A" = linkonce_odr global %struct.S zeroinitializer
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// CHECK-DAG: @"\01?$TSS0@?1??h@@YAAAUS@@_N@Z@4HA" = linkonce_odr global i32 0
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// CHECK-DAG: @"\01?i@?1??g1@@YAHXZ@4HA" = internal global i32 0, align 4
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// CHECK-DAG: @"\01?$TSS0@?1??g1@@YAHXZ@4HA" = internal global i32 0, align 4
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// CHECK-LABEL: define {{.*}} @"\01?f@@YAAAUS@@XZ"()
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// CHECK-SAME: personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*)
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extern inline S &f() {
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static thread_local S s;
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// CHECK: %[[guard:.*]] = load i32, i32* @"\01??__J?1??f@@YAAAUS@@XZ@51"
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// CHECK-NEXT: %[[mask:.*]] = and i32 %[[guard]], 1
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// CHECK-NEXT: %[[cmp:.*]] = icmp eq i32 %[[mask]], 0
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// CHECK-NEXT: br i1 %[[cmp]], label %[[init:.*]], label %[[init_end:.*]], !prof ![[unlikely_threadlocal:.*]]
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//
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// CHECK: [[init]]:
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// CHECK-NEXT: %[[or:.*]] = or i32 %[[guard]], 1
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// CHECK-NEXT: store i32 %[[or]], i32* @"\01??__J?1??f@@YAAAUS@@XZ@51"
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// CHECK-NEXT: invoke {{.*}} @"\01??0S@@QAE@XZ"(%struct.S* @"\01?s@?1??f@@YAAAUS@@XZ@4U2@A")
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// CHECK-NEXT: to label %[[invoke_cont:.*]] unwind label %[[lpad:.*]]
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//
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// CHECK: [[invoke_cont]]:
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// CHECK-NEXT: call i32 @__tlregdtor(void ()* @"\01??__Fs@?1??f@@YAAAUS@@XZ@YAXXZ")
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// CHECK-NEXT: br label %[[init_end:.*]]
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// CHECK: [[init_end]]:
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// CHECK-NEXT: ret %struct.S* @"\01?s@?1??f@@YAAAUS@@XZ@4U2@A"
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// CHECK: [[lpad:.*]]:
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// CHECK-NEXT: cleanuppad within none []
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// CHECK: %[[guard:.*]] = load i32, i32* @"\01??__J?1??f@@YAAAUS@@XZ@51"
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// CHECK-NEXT: %[[mask:.*]] = and i32 %[[guard]], -2
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// CHECK-NEXT: store i32 %[[mask]], i32* @"\01??__J?1??f@@YAAAUS@@XZ@51"
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// CHECK-NEXT: cleanupret {{.*}} unwind to caller
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return s;
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}
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// CHECK-LABEL: define {{.*}} @"\01?g@@YAAAUS@@XZ"()
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extern inline S &g() {
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static S s;
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// CHECK: %[[guard:.*]] = load atomic i32, i32* @"\01?$TSS0@?1??g@@YAAAUS@@XZ@4HA" unordered, align 4
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// CHECK-NEXT: %[[epoch:.*]] = load i32, i32* @_Init_thread_epoch
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// CHECK-NEXT: %[[cmp:.*]] = icmp sgt i32 %[[guard]], %[[epoch]]
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// CHECK-NEXT: br i1 %[[cmp]], label %[[init_attempt:.*]], label %[[init_end:.*]], !prof ![[unlikely_staticlocal:.*]]
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//
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// CHECK: [[init_attempt]]:
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// CHECK-NEXT: call void @_Init_thread_header(i32* @"\01?$TSS0@?1??g@@YAAAUS@@XZ@4HA")
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// CHECK-NEXT: %[[guard2:.*]] = load atomic i32, i32* @"\01?$TSS0@?1??g@@YAAAUS@@XZ@4HA" unordered, align 4
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// CHECK-NEXT: %[[cmp2:.*]] = icmp eq i32 %[[guard2]], -1
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// CHECK-NEXT: br i1 %[[cmp2]], label %[[init:.*]], label %[[init_end:.*]]
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//
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// CHECK: [[init]]:
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// CHECK-NEXT: invoke {{.*}} @"\01??0S@@QAE@XZ"(%struct.S* @"\01?s@?1??g@@YAAAUS@@XZ@4U2@A")
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// CHECK-NEXT: to label %[[invoke_cont:.*]] unwind label %[[lpad:.*]]
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//
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// CHECK: [[invoke_cont]]:
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// CHECK-NEXT: call i32 @atexit(void ()* @"\01??__Fs@?1??g@@YAAAUS@@XZ@YAXXZ")
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// CHECK-NEXT: call void @_Init_thread_footer(i32* @"\01?$TSS0@?1??g@@YAAAUS@@XZ@4HA")
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// CHECK-NEXT: br label %init.end
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//
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// CHECK: [[init_end]]:
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// CHECK-NEXT: ret %struct.S* @"\01?s@?1??g@@YAAAUS@@XZ@4U2@A"
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//
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// CHECK: [[lpad]]:
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// CHECK-NEXT: cleanuppad within none []
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// CHECK: call void @_Init_thread_abort(i32* @"\01?$TSS0@?1??g@@YAAAUS@@XZ@4HA")
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// CHECK-NEXT: cleanupret {{.*}} unwind to caller
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return s;
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}
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extern inline S&h(bool b) {
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static thread_local S j;
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static S i;
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return b ? j : i;
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}
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// CHECK-LABEL: define i32 @"\01?g1@@YAHXZ"()
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int f1();
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int g1() {
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static int i = f1();
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return i;
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}
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// CHECK-DAG: ![[unlikely_threadlocal]] = !{!"branch_weights", i32 1, i32 1023}
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// CHECK-DAG: ![[unlikely_staticlocal]] = !{!"branch_weights", i32 1, i32 1048575}
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