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https://issues.apache.org/jira/browse/STDCXX-335?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martin Sebor updated STDCXX-335:
--------------------------------
Fix Version/s: 4.3
Not sure we'll be able to do anything about this w/o the blessing of the
committee since changing the signature of the function would be easily
detectable even for fundamental types. See the test case below. Scheduled for
4.3.
#include <cassert>
#include <algorithm>
int main ()
{
int x = 0;
int y = 2;
const int &z = std::min (x, y);
x = 1;
assert (&z == &x);
assert (z == 1);
}
> std::min() suboptimal
> ---------------------
>
> Key: STDCXX-335
> URL: https://issues.apache.org/jira/browse/STDCXX-335
> Project: C++ Standard Library
> Issue Type: Bug
> Components: 25. Algorithms
> Affects Versions: 4.1.3
> Environment: gcc 3.2.3, x86 Linux
> Reporter: Mark Brown
> Fix For: 4.3
>
>
> I don't know if it's the compiler that's generating worse code for the stdcxx
> version of min or if the function is not implemented as efficiently as it
> could be but the disassembly for the two functions below shows that my_min()
> is one instruction shorter than test_min():
> #include <algorithm>
> int test_min (int x, int y) { return std::min (x, y); }
> int my_min (int x, int y) { return x < y ? x : y; }
> _Z8test_minii:
> pushl %ebp
> movl %esp, %ebp
> movl 12(%ebp), %eax
> cmpl %eax, 8(%ebp)
> jg .L2
> leal 8(%ebp), %eax <<< extra load?
> .L4:
> movl (%eax), %eax
> leave
> ret
> _Z6my_minii:
> pushl %ebp
> movl %esp, %ebp
> movl 12(%ebp), %eax
> cmpl 8(%ebp), %eax
> jle .L6
> movl 8(%ebp), %eax
> .L6:
> leave
> ret
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