Implement first D-specific optimization pass: -simplify-drtcalls. It uses the machinery of the standard -simplify-libcalls pass, but optimizes calls to the D runtime instead of calls to C libraries. At the moment, these optimizations are implemented by this pass: - Avoid the runtime call for `arr.length = newlen` if it can determine that the new length isn't longer than the old one. - Ditto for `cast(T[]) arr` if it will clearly always succeed. (e.g. if the length of the original array is zero, or if the old element size is a multiple of the new element size)

#ifndef LDC_GEN_OPTIMIZER_H
#define LDC_GEN_OPTIMIZER_H

namespace llvm { class Module; }

bool ldc_optimize_module(llvm::Module* m);

bool doInline();

int optLevel();

bool optimize();

#endif