The migration tool generates C++ code that invokes methods in the virtual machine, which is also C++. As such, it relies heavily on the compiler to achieve an efficient translation. In particular, the following compiler optimizations are critical for VCOP translation:

• Inlining. The virtual machine is implemented as C++ classes with static inline methods. The migration tool expects the compiler to inline them fully. The vloops() function of a translated kernel should contain no calls.
• Software pipelining. This is an important key to performance on C7x. The compiler should be able to pipeline any loop generated by the migration tool for a VCOP kernel.
• #pragma PARALLEL_LOOP. There are no loop-carried memory dependencies in a VCOP kernel (this is a built-in property of the architecture). The migration tool uses the PARALLEL_LOOP pragma to convey this property to the compiler. The compiler must not limit the initiation interval of a software pipelined loop due to memory dependence.
• NLC. The migration tool does not directly invoke the NLC. It expresses loop control using explicit loops and relies on the compiler to collapse them using the NLC where appropriate.
• Hoisting. The migration tool generates many loop-invariant operations within inner loops and relies on the compiler to recognize that they are invariant and hoist them outside the loop.
• Forward Substitution for Addressing Primitives. The migration tool generates SE- and SA-based loads as move instructions with the SE/SA pseudo-register as the source operand. Since this operand encodes as a register operand, it can be often be propagated to where it’s used. For example, the sequence:

     VMV SE0++,Vreg1
     ...
     VADDW Vreg1,Vreg2,Vdst
  

  can be optimized to:

     VADDW SE0++,Vreg2,Vdst
  

  A related issue is that the migration tool sometimes generates SA-based references to objects separately from the actual indirection. The compiler should combine these. For example, the migration tool may generate:

     int16 *p = &__sa_noadv_int(0, 4, base); // note “address of”
     ...
     *p = Vreg; 
  

  this generates:

     ADDAW reg_base, SA0++, reg_p
     ...
     VSTW Vreg,*reg_p
  

  which should be optimized to:

     VSTW Vreg,*reg_base[SA0++]
  

This is by no means an exhaustive list. Efficient translation relies on dozens of compiler optimizations, not all of which have been implemented.