Hi,

I am just trying to fiddle around what is the best and shortest way to describe two simple instructions with C-like pseudo code. The extract instruction is defined as follows:

extract rd, rs, imm

This instruction extracts the appropriate byte from the 32-bit source register rs and right justifies it in the destination register. The byte is specified by imm and thus can take the values 0 (for the least-significant byte) and 3 (for the most-significant byte).

rd = 0x0;  // zero-extend result, ie to make sure bits 31 to 8 are set to zero in the result
rd = (rs && (0xff << imm)) >> imm; // this extracts the approriate byte and stores it in rd

The insert instruction can be regarded as the inverse operation and it takes a right justified byte from the source register rs and deposits it in the appropriate byte of the destination register rd; again, this byte is determined by the value of imm

tmp = 0x0 XOR (rs << imm)) // shift the byte to the appropriate byte determined by imm
rd = (rd && (0x00 << imm)) // set appropriate byte to zero in rd
rd = rd XOR tmp            // XOR the byte into the destination register

This looks all a bit horrible, so I wonder if there is a little bit a more elegant way to describe this bahaviour in C-like style ;)

Many thanks, Claus