https://llvm.org/bugs/show_bug.cgi?id=28844
Bug ID: 28844
Summary: Code is not optimized with -O2 when used with variadic
arguments
Product: clang
Version: 3.9
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: k...@jusiak.net
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 16881
--> https://llvm.org/bugs/attachment.cgi?id=16881&action=edit
Simple case demonstrating the bug
Started to happen in 3.9 and trunk. Previous versions work fine.
struct config {
static int f(...) { return 42; }
};
int main() {
return config::f();
}
Clang-3.9: compiled with -O2 -S gives:
xor %eax,%eax
jmpq 0x403540 <_ZN6config1fEz>
Clang-3.8 or less, or GCC, or MSVC gives:
movl $42, %eax
retq
It's just a simplified example, however, technic with variadic args is popular
in the context of SFINAE.
Due to this issue C++14 dependency injection library
(https://github.com/boost-experimental/di) is not optimizing bindings with
clang-3.9.
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