Imagecraft c compiler and development environment for the atmel avr

ICCV8 for AVR – C Compiler for Atmel AVROptimizationsImageCraft compilers are derived from the LCC compiler (see Acknowledgments). Assuch, the portable front end of the LCC compilers perform the following optimizations: Algebraic Simplifications and Constant Folding.The compiler may replace expensive algebraic expressions with simplerexpressions (e.g., adding by 0, dividing by 1, etc.). The compiler also evaluatesconstant expressions and “folds” them (e.g., 1+1 becomes 2). The compiler alsoperforms these optimizations on floating-point constants and the results may beslightly different if the floating-point constants are not “folded.” This is because theprecision and range of the floating-point operations of the host CPU (e.g., Intelprocessors) differ from the target CPU. In most cases, any minor differences willnot be an issue. Basic Block Common Subexpression Elimination.Expressions that are reused within a basic block (i.e., a sequence of straight linecode without jumps) may be cached in a compiler-created temporary and notrecomputed. Switch Optimizations.The compiler analyzes the switch values and generates code using a combinationof binary searches and jump tables. The jump tables are effective for denselypacked switch values and the binary searches locate the right jump table quickly.In the case where the values are widely spread or few in numbers, a simple ifthen-elsesearch is performed.The compiler code generator (the “backend”) uses a technique called bottom-up treerewriting with dynamic programming to generate assembly code, meaning that thegenerated code is locally (i.e., per expression) optimal. In addition, the backend mayperform the following optimizations. Note that these are ImageCraft enhancementsand not part of the standard LCC distribution. Peephole Optimizations.While locally optimal, the generated code may still have redundant fragmentsresulting from different C statements. Peephole optimizations eliminate some ofthese redundancies. Register Allocation.For targets with multiple machine registers (e.g., AVR, MSP430, and ARM), foreach function, the compiler performs register allocation and tries to pack as manylocal variables as possible into the machine registers and thereby increase23