a425623dd9
Summary: Often, a code will call multiple virtual methods of a given object. If they go in a linear block, it should be possible to check vtable before the first call, then store vtable pointer and reuse it for the second vcall without any additional checks. This is expected to have a positive performance impact on a hot path in Blink, see https://crbug.com/634139. Reviewers: kcc Differential Revision: https://reviews.llvm.org/D23151 llvm-svn: 277795
61 lines
1.2 KiB
C++
61 lines
1.2 KiB
C++
// RUN: %clangxx_cfi_diag -o %t %s
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// RUN: %t 2>&1 | FileCheck %s
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// This test checks that we don't generate two type checks,
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// if two virtual calls are in the same function.
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// UNSUPPORTED: win32
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// REQUIRES: cxxabi
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// TODO(krasin): implement the optimization to not emit two type checks.
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// XFAIL: *
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#include <stdio.h>
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class Base {
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public:
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virtual void Foo() {
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fprintf(stderr, "Base::Foo\n");
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}
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virtual void Bar() {
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fprintf(stderr, "Base::Bar\n");
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}
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};
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class Derived : public Base {
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public:
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void Foo() override {
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fprintf(stderr, "Derived::Foo\n");
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}
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void Bar() override {
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printf("Derived::Bar\n");
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}
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};
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__attribute__((noinline)) void print(Base* ptr) {
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ptr->Foo();
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// Corrupt the vtable pointer. We expect that the optimization will
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// check vtable before the first vcall then store it in a local
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// variable, and reuse it for the second vcall. With no optimization,
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// CFI will complain about the virtual table being corrupted.
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*reinterpret_cast<void**>(ptr) = 0;
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ptr->Bar();
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}
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int main() {
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Base b;
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Derived d;
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// CHECK: Base::Foo
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// CHECK: Base::Bar
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print(&b);
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// CHECK: Derived::Foo
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// CHECK-NOT: runtime error
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// CHECK: Derived::Bar
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print(&d);
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return 0;
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}
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