Imagecraft c compiler and development environment for the atmel avr

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ICCV8 for AVR – C Compiler for Atmel AVRgenerated code performance. We use a sophisticated algorithm that analyzes thevariable usage (e.g., the program range where it is used) and may even putmultiple variables into the same register if their usages do not overlap.This may cause confusion while debugging, as variables may seem to changevalues when you don’t expect them to change. However, this is correct if theregister previously allocated to a variable is now allocated to a different variable.Register History.This works in tandem with the register allocator. It tracks the contents of theregisters and eliminates copies and other similar optimizations.Code Compressor (tm)The Code Compressor is available on the ADVANCED and PROFESSIONALversions of selected compilers. It works after the entire program is linked and replacescommonly used code fragments with function calls. It can decrease a program size byas much as 30% (typical value is 5% to 15%) without incurring too much of anexecution speed slowdown. See Code Compressor (tm).Machine Independent Optimizer (MIO)MIO is a state-of-the-art function-level optimizer, available on the PROFESSIONALversions of selected compilers. It performs the following optimizations on a functionlevel, taking into consideration the effect of control flow structures: Constant Propagation.Assigning constants to a local variable is tracked and the use of the variable isreplaced by the constant if possible. Combined with constant folding, this can be avery effective optimization. Global Value Numbering.Similar to Common Subexpression Elimination. This replaces redundantexpressions at a function level. Loop Invariant Code Motion.Expressions that do not change inside loops are moved outside. Advanced Register Allocation.The already powerful register allocator is augmented by a “web” (different fromthe Internet web) building process that effectively treats different uses of a singlevariable as multiple variables, allowing even better register allocation to beperformed.24
ICCV8 for AVR – C Compiler for Atmel AVR Advanced Local Variable Stack Allocation.Even with the advanced register allocator, sometimes the target CPU just doesnot have enough machine registers to keep all of the candidate local variables inregisters. These unallocated variables must be put on the stack. However, a largestack offset is generally less efficient on most target CPUs. By utilizing the samefast algorithm, the backend packs the unallocated variables optimally, sharingspace with each other if possible, reducing the total size of the function stackframe.ImageCraft has invested a considerable amount of effort on putting a state-of-the-artoptimizer infrastructure in place. Currently the MIO optimizations benefit mainlyexecution speed and some small improvement in code size. We will continue to tunethe optimizer and add in new optimizations as time progresses.The code compression optimization may be enabled in addition to the MIOoptimizations. This combination gives you the smallest code while alleviating some ofthe speed degradation introduced by the Code Compressor.Mixed Arithmetic Type OptimizationsImageCraft compilers minimize the integer promotions dictated by the C Standard aslong as the correct results are produced. The base STANDARD performs basicoptimizations (e.g., byte operations are used whenever possible for 8-bit targets) andthe PROFESSIONAL edition perform more aggressive optimizations (e.g. ,16-bitmultiply with 32-bit result is used when it makes sense rather than promoting bothoperands to 32-bits and then use the slower 32-bit multiply).25
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Imagecraft c compiler and development environment for the atmel avr

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