[LLVMbugs] [Bug 9447] New: Adding a copy constructor that is the same as the default generates worse code

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=9447

           Summary: Adding a copy constructor that is the same as the
                    default generates worse code
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: jmuizelaar at mozilla.com
                CC: llvmbugs at cs.uiuc.edu


struct point
{
        double x, y;
        point(double x, double y) : x(x), y(y) {}
        point(const point& p) : x(p.x), y(p.y) {}
};

void get_point(void *c, double *x, double *y);

class c {
        int count;
        void *p;
        point getPoint();
};
point c::getPoint(){
                double x, y;
                get_point(p, &x, &y);
                return point(x, y);

        }

Compiles to:

_ZN1c8getPointEv:                       # @_ZN1c8getPointEv
        pushq   %rbp
        movq    %rsp, %rbp
        subq    $16, %rsp
        movq    8(%rdi), %rdi
        leaq    -8(%rbp), %rsi
        leaq    -16(%rbp), %rdx
        callq   _Z9get_pointPvPdS0_
        movsd   -8(%rbp), %xmm0
        movsd   -16(%rbp), %xmm1
        addq    $16, %rsp
        popq    %rbp
        ret


With the copy-constructor commented out we get:

_ZN1c8getPointEv:                       # @_ZN1c8getPointEv
        pushq   %rbp
        movq    %rsp, %rbp
        pushq   %rbx
        subq    $24, %rsp
        movq    %rdi, %rbx
        movq    8(%rsi), %rdi
        leaq    -16(%rbp), %rsi
        leaq    -24(%rbp), %rdx
        callq   _Z9get_pointPvPdS0_
        movsd   -24(%rbp), %xmm0
        movsd   -16(%rbp), %xmm1
        movsd   %xmm1, (%rbx)
        movsd   %xmm0, 8(%rbx)
        movq    %rbx, %rax
        addq    $24, %rsp
        popq    %rbx
        popq    %rbp
        ret

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