[PATCH] D35145: Use emplace_back to replace size() and resize().

[Dehao Chen via Phabricator via llvm-commits]

danielcdh added a comment.

Looks like it's implementation dependent, both gcc and clang uses loop to implement std::list::size:

#cat test.cc
#include <list>

int p(std::list<int> t) {

  return t.size();

}
#g++ --std=c++11 test.cc -S -O2 -o - |grep jne -B4
.L4:
	movq	(%rdx), %rdx
	addq	$1, %rax
	cmpq	%rdx, %rdi
	jne	.L4
https://reviews.llvm.org/tag/clang/ --std=c++11 test.cc -S -O2 -o - |grep jne -B4
.LBB0_1:                                # =>This Inner Loop Header: Depth=1
	movq	(%rcx), %rcx
	incl	%eax
	cmpq	%rcx, %rdi
	jne	.LBB0_1


https://reviews.llvm.org/D35145