andrew.zhogin created this revision. andrew.zhogin added a reviewer: majnemer. andrew.zhogin added subscribers: zinovy.nis, cfe-commits.
Clang generates aliases for vtable access getelementptr (microsoft ABI only). It breaks devirtualization due to constprop failing on GlobalAlias. Here is simple test aka "return ptr->f() + ptr->f_const()". Linked with: [[ http://reviews.llvm.org/D11306 | llvm patch for aliases constprop ]] http://reviews.llvm.org/D11315 Files: test/Analysis/devirtualize-virtual-function-calls-constprop.cpp Index: test/Analysis/devirtualize-virtual-function-calls-constprop.cpp =================================================================== --- test/Analysis/devirtualize-virtual-function-calls-constprop.cpp +++ test/Analysis/devirtualize-virtual-function-calls-constprop.cpp @@ -0,0 +1,16 @@ +// RUN: %clang_cc1 -O3 %s -emit-llvm -o - | FileCheck %s +// RUN: %clang_cc1 -O3 %s -triple x86_64-win32 -emit-llvm -o - | FileCheck %s + +struct A { + virtual int f() { return 7; } + virtual int f_const() const { return 3; } +}; + +// CHECK: ret i32 10 +int f() { + A *ptr = new A(); + + int rv = ptr->f() + ptr->f_const(); + delete ptr; + return rv; +}
Index: test/Analysis/devirtualize-virtual-function-calls-constprop.cpp =================================================================== --- test/Analysis/devirtualize-virtual-function-calls-constprop.cpp +++ test/Analysis/devirtualize-virtual-function-calls-constprop.cpp @@ -0,0 +1,16 @@ +// RUN: %clang_cc1 -O3 %s -emit-llvm -o - | FileCheck %s +// RUN: %clang_cc1 -O3 %s -triple x86_64-win32 -emit-llvm -o - | FileCheck %s + +struct A { + virtual int f() { return 7; } + virtual int f_const() const { return 3; } +}; + +// CHECK: ret i32 10 +int f() { + A *ptr = new A(); + + int rv = ptr->f() + ptr->f_const(); + delete ptr; + return rv; +}
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