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50145cc3e9
Summary:
By manipulating a local variable in the loop, when the loop can
be optimized away (due to no non-trivial destructors), this lets
it be fully optimized away and we modify the __end_ separately.
This results in a substantial improvement in the generated code.
Prior to this change, this would be generated (on x86_64):
movq (%rdi), %rdx
movq 8(%rdi), %rcx
cmpq %rdx, %rcx
je LBB2_2
leaq -12(%rcx), %rax
subq %rdx, %rax
movabsq $-6148914691236517205, %rdx ## imm = 0xAAAAAAAAAAAAAAAB
mulq %rdx
shrq $3, %rdx
notq %rdx
leaq (%rdx,%rdx,2), %rax
leaq (%rcx,%rax,4), %rax
movq %rax, 8(%rdi)
And after:
movq (%rdi), %rax
movq %rax, 8(%rdi)
This brings this in line with what other implementations do.
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D25241
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@298601 91177308-0d34-0410-b5e6-96231b3b80d8
41 lines
953 B
C++
41 lines
953 B
C++
//===----------------------------------------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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// <vector>
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// void clear();
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#include <vector>
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#include <cassert>
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#include "min_allocator.h"
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#include "asan_testing.h"
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int main()
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{
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{
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int a[] = {1, 2, 3};
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std::vector<int> c(a, a+3);
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c.clear();
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assert(c.empty());
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LIBCPP_ASSERT(c.__invariants());
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LIBCPP_ASSERT(is_contiguous_container_asan_correct(c));
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}
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#if TEST_STD_VER >= 11
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{
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int a[] = {1, 2, 3};
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std::vector<int, min_allocator<int>> c(a, a+3);
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c.clear();
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assert(c.empty());
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LIBCPP_ASSERT(c.__invariants());
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LIBCPP_ASSERT(is_contiguous_container_asan_correct(c));
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}
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#endif
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}
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