RISC-V lw, sw, Decision I Intro 编译器会最小化寄存器使用 layout in Memory side note: a register is a 32-bit register(hold 32-bit data) word: 4 bytes, 32 bits risc-v 小端法（主流） Data Transfer Instructions lw (load word) look note 🤔 sw (store word) 结合lec7的模式图来记忆 lb/sb (load byte/store byte) same as lw/sw lb 符号扩展 lbu: load byte unsigned why still addi? 更快 但是imm的范围更小 (32bit以内) Decision I RV32 so far 😋 1 2 3 4 5 6 7 8 add rd, rs1, rs2 sub rd, rs1, rs2 addi rd, rs1, imm lw rd, imm(rs1) sw rs2, imm(rs1) lb rd, imm(rs1) sb rs2, imm(rs1) lbu rd, imm(rs1) beq/bne (branch if equal/not equal) Decision in RISC-V Assembly beq: branch if equal bne: branch if not equal blt: branch if less than blt reg1, reg2, label # if (reg1 < reg2) goto label bge: branch if greater than or equal bltu: branch if unsigned less than bltu reg1, reg2, label # if (reg1 < reg2) goto label bgeu: branch if unsigned greater than or equal j: jump/always branch j label # 无条件jump的范围比有条件jump构造出来的无条件jump更大（32位限制） 没有：bgt or ble, only have BLT（培根生菜番茄） sandwiches

C intro: Pointers, Arrays, Strings Pointers 1 int (*fn) (void *, void *) = &foo; // pointer to function arrow operator -> is used to access members of a struct pointed to by a pointer. NULL pointer is used to indicate an invalid pointer. 1 2 3 if (p == NULL) { // handle error } 谈到了地址对齐 -> word alignment 1 2 3 sizeof(arg) sizeof(structtype) Arrays 经典问题之数组名是指针 1 2 3 4 5 char *foo() { char arr[10]; return arr; // A BIG mistake!

Great Ideas in Computer Architecture Intro six great ideas Moore’s Law Abstraction Principle of Locality / Memory Hierarchy Parallelism Performance Measurement & Improvement Dependability via Redundancy 😉