Sun Studio 12: Performance Analyzer

Cloned Functions

The compilers have the ability to recognize calls to a function for which extra optimization can be performed. An example of such is a call to a function where some of the arguments passed are constants. When the compiler identifies particular calls that it can optimize, it creates a copy of the function, which is called a clone, and generates optimized code.

In the annotated source, compiler commentary indicates if a cloned function has been created:

0.       0.       Function foo from source file clone.c cloned, 
                   creating cloned function _$; 
                   constant parameters propagated to clone
0.       0.570     27.    foo(100, 50, a, a+50, b);

Note –

Compiler commentary lines do not wrap in the real annotated source display.

The clone function name is a mangled name that identifies the particular call. In the above example, the compiler commentary indicates that the name of the cloned function is _$ This function can be seen in the function list as follows:

0.350     0.550     foo
0.340     0.570     _$

Each cloned function has a different set of instructions, so the annotated disassembly listing shows the cloned functions separately. They are not associated with any source file, and therefore the instructions are not associated with any source line numbers. The following shows the first few lines of the annotated disassembly for a cloned function.

0.       0.           <Function: _$>
0.       0.           [?]    10e98:  save        %sp, -120, %sp
0.       0.           [?]    10e9c:  sethi       %hi(0x10c00), %i4
0.       0.           [?]    10ea0:  mov         100, %i3
0.       0.           [?]    10ea4:  st          %i3, [%i0]
0.       0.           [?]    10ea8:  ldd         [%i4 + 640], %f8