SPARC Assembly/Memory Instructions

Instruction Format This is going to be a quick primer for how to write these memory instructions. Load Instruction Format Memory instructions load a value from memory, or store a value into memory. The target address is computed as the addition of a base value with an optional offset value. For example: ld [%r4 + 10], %r5 loads the register %r5 with the value in memory located at [%r4 + 10]. If %r4 contains the number 25, then the memory location read would be [25 + 10] = 35. The op2 parameter, like the arithmetic instructions can be a register or an immediate. This means that the following are both valid: ld [%r4 + %r3], %r5 ld [%r4 + 100], %r5 The offset value is the number of bytes offset, not the number of machine words or halfwords. This means that to load consecutive words on a 32 bit machine, the offset needs to be incremented by 4: ld [%r4 + 4], %r5 ld [%r4 + 8], %r6 ... Also, the offset value is optional. If the offset is omitted, the assembler will assume a value of 0. For example: ld [%r4], %r5 will read from location %r4, with no offset. Store Instruction Format Store instructions are similar to load instructions, except that the operands are reversed. This means that we have the following instruction format: st rd, [rs1 + op2] All the rest of the above material applies. Load Instructions ldub Loads an unsigned byte from memory into rd. ldsb loads a signed byte from memory into rd. sign-extends result. lduh loads an unsigned halfword from memory into rd. ldsh loads a signed halfword from memory into rd. Sign extends result. ld loads a machine word into rd. ldd Loads a double word into 2 consecutive registers. Store Instructions stb Stores a byte from register rd into memory. sth stores a halfword from register rd into memory. st stores a machine word from register rd into memory. std stores a double value from two consecutive registers into memory. Swap Instruction swap performs a simultaneous load and store operation, which effectively swaps the value in memory with the value in rd. Is formatted like a load instruction, for example: swap [%r3 + 4], %r5