http://llvm.org/bugs/show_bug.cgi?id=17151
Bug ID: 17151
Summary: missed optimization: unused std::string
Product: clang
Version: unspecified
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: C++
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
>cat test.cpp
#include <string>
void foo() {
std::string a = "abc";
}
void boo() {
}
Expected, that both 'foo' and 'boo' produce same asm, but it's not:
>clang++ -O3 -stdlib=libc++ -save-temps -O3 -c -fomit-frame-pointer test.cpp
>cat test.s
__Z3foov: ## @_Z3foov
pushq %rbx
subq $32, %rsp
leaq 8(%rsp), %rbx
leaq L_.str(%rip), %rsi
movq %rbx, %rdi
movl $3, %edx
callq
__ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEPKcm
movq %rbx, %rdi
callq
__ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEED1Ev
addq $32, %rsp
popq %rbx
ret
__Z3boov: ## @_Z3boov
ret
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