CSE 425: Target Machine Architecture

Target Machine Details• Many architectures can be similar in overall structure

– E.g., Von Neumann with CISC instruction sets is common– RISC architectures also have been used and still are

• For programming languages, architecture of the target machine also imposes a number of details to consider– Especially to retarget a compiler to another machine– Especially to write software that’s portable across machines– E.g., sizes, other details of memory locations and addresses

• Programming language details often based on them– Sizes and layouts of data types, aliases, objects, etc.– Addresses, how incremented/decremented pointers move,

relative to other variables address space (local, array, heap) – Directions stack and heap grow in memory address space

CSE 425: Target Machine Architecture

Example Data Size Rules (from C++)• Rules governing data sizes [from Stroustrup 4th Ed]

– R1: 1 == sizeof(char) <= sizeof(short) <= sizeof(int)

<= sizeof(long) <= sizeof(long long)– R2: 1 <= sizeof(bool) <= sizeof(long)– R3: sizeof(char) <= sizeof(wchar_t) <= sizeof(long)– R4: sizeof(float) <= sizeof(double) <= sizeof(long double)– R5: sizeof(N) == sizeof(signed N) == sizeof(unsigned N)

where N is char, short, int, long, or long long (integral types)

• Minimum data sizes for some types [from LLM 5th Ed]– R6: char must be at least 1 byte (8 bits) – R7: wchar_t, char16_t, short, int must be at least 2 bytes– R8: char32_t and long must be at least 4 bytes– R9: long long must be at least 8 bytes

CSE 425: Target Machine Architecture

Today’s Studio Exercises

• We’ll look at some target machine details today– Data sizes, pointer addresses, etc.

• Today’s exercises are again in C++– Please take advantage of the on-line reference manual

pages that are linked on the course web site– As always, please ask us for help as needed

• When done, send email with “Target Machine Studio” in the subject line to the cse425@seas.wustl.edu course account