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
55 lines
2.4 KiB
C++
55 lines
2.4 KiB
C++
// RUN: %clang_cc1 -emit-llvm -triple=wasm32-unknown-unknown -o - %s \
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// RUN: | FileCheck %s -check-prefix=WEBASSEMBLY32
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// RUN: %clang_cc1 -emit-llvm -triple=wasm64-unknown-unknown -o - %s \
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// RUN: | FileCheck %s -check-prefix=WEBASSEMBLY64
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// Test that we don't create common blocks.
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int tentative;
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// WEBASSEMBLY32: @tentative = global i32 0, align 4
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// WEBASSEMBLY64: @tentative = global i32 0, align 4
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// Test that WebAssembly uses the ARM-style ABI in which the static
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// variable's guard variable is tested via "load i8 and test the
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// bottom bit" rather than the Itanium/x86 ABI which uses "load i8
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// and compare with zero".
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int f();
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void g() {
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static int a = f();
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}
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// WEBASSEMBLY32-LABEL: @_Z1gv()
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// WEBASSEMBLY32: %[[R0:.+]] = load atomic i8, i8* bitcast (i32* @_ZGVZ1gvE1a to i8*) acquire, align 4
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// WEBASSEMBLY32-NEXT: %[[R1:.+]] = and i8 %[[R0]], 1
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// WEBASSEMBLY32-NEXT: %[[R2:.+]] = icmp eq i8 %[[R1]], 0
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// WEBASSEMBLY32-NEXT: br i1 %[[R2]], label %[[CHECK:.+]], label %[[END:.+]],
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// WEBASSEMBLY32: [[CHECK]]
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// WEBASSEMBLY32: call i32 @__cxa_guard_acquire
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// WEBASSEMBLY32: [[END]]
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// WEBASSEMBLY32: call void @__cxa_guard_release
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//
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// WEBASSEMBLY64-LABEL: @_Z1gv()
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// WEBASSEMBLY64: %[[R0:.+]] = load atomic i8, i8* bitcast (i64* @_ZGVZ1gvE1a to i8*) acquire, align 8
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// WEBASSEMBLY64-NEXT: %[[R1:.+]] = and i8 %[[R0]], 1
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// WEBASSEMBLY64-NEXT: %[[R2:.+]] = icmp eq i8 %[[R1]], 0
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// WEBASSEMBLY64-NEXT: br i1 %[[R2]], label %[[CHECK:.+]], label %[[END:.+]],
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// WEBASSEMBLY64: [[CHECK]]
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// WEBASSEMBLY64: call i32 @__cxa_guard_acquire
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// WEBASSEMBLY64: [[END]]
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// WEBASSEMBLY64: call void @__cxa_guard_release
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// Test various aspects of static constructor calls.
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struct A {
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A();
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};
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A theA;
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// WEBASSEMBLY32: define internal void @__cxx_global_var_init() #3 section ".text.__startup" {
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// WEBASSEMBLY32: call %struct.A* @_ZN1AC1Ev(%struct.A* @theA)
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// WEBASSEMBLY32: define internal void @_GLOBAL__sub_I_static_init_wasm.cpp() #3 section ".text.__startup" {
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// WEBASSEMBLY32: call void @__cxx_global_var_init()
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//
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// WEBASSEMBLY64: define internal void @__cxx_global_var_init() #3 section ".text.__startup" {
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// WEBASSEMBLY64: call %struct.A* @_ZN1AC1Ev(%struct.A* @theA)
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// WEBASSEMBLY64: define internal void @_GLOBAL__sub_I_static_init_wasm.cpp() #3 section ".text.__startup" {
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// WEBASSEMBLY64: call void @__cxx_global_var_init()
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