%r8 %r8d. %r9 %r9d. %r10 %r10d. %r11 %r11d. %r12 %r12d. %r13 %r13d. %r14 %r14d %rbp. %r15 %r15d. Sean Barker

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1 Procedure Call Registers Return %rax %eax %r8 %r8d Arg 5 %rbx %ebx %r9 %r9d Arg 6 Arg 4 %rcx %ecx %r10 %r10d Arg 3 %rdx %edx %r11 %r11d Arg 2 %rsi %esi %r12 %r12d Arg 1 %rdi %edi %r13 %r13d ptr %esp %r14 %r14d %ebp %r15 %r15d 1 Switch Statements long switch_eg (long x, long y, long z) { long w = 1; switch(x) { case 1: w = y*z; case 2: w = y/z; /* Fall Through */ case 3: w += z; case 5: case 6: w -= z; default: w = 2; return w; 2

$Jump Tables Switch Form switch(x) { case val_0: Block 0 case val_1: Block 1 case val_n-1: Block n 1 jtab: Jump Table Targ0 Targ1 Targ2 Targn-1 Targ0: Targ1: Targ2: Code Block 0 Code Block 1 Code$

2 Jump Tables Switch Form switch(x) { case val_0: Block 0 case val_1: Block 1 case val_n-1: Block n 1 jtab: Jump Table Targ0 Targ1 Targ2 Targn-1 Targ0: Targ1: Targ2: Code Block 0 Code Block 1 Code Block 2 Transla:on (Extended C) goto *jtab[x]; Targn-1: Code Block n 1 3 Switch Example long switch_eg (long x, long y, long z) { long w = 1; switch(x) { case 1: w = y*z; case 2: w = y/z; /* Fall Through */ case 3: w += z; case 5: case 6: w -= z; default: w = 2; return w; Jump table.section.rodata.align 8.L4:.quad.L8 # x = 0.quad.L3 # x = 1.quad.L5 # x = 2.quad.L9 # x = 3.quad.L8 # x = 4.quad.L7 # x = 5.quad.L7 # x = 6 switch_eg: movq %rdx, %rcx cmpq $6, %rdi # x:6 ja.l8 # Use default jmp *.L4(,%rdi,8) # goto *JTab[x] 4

Example Jump Table Jump table.section.rodata.align 8.L4:.quad.L8 # x = 0.quad.L3 # x = 1.quad.L5 # x = 2.quad.L9 # x = 3.

L5 w = y/z; /* Fall Through */ case 3: //.L9 w += z; case 5: case 6: //.L7 w -= z; default: //.

L8 w = 2; return w; switch_eg: movq %rdx, %rcx cmpq $6, %rdi # x:6 ja.l8 # Use default jmp *.

l5: # Case 2 movq %rsi, %rax cqto idivq %rcx # y/z jmp.l6 # goto merge.l9: # Case 3 movl $1, %eax # w = 1.

3 Example Jump Table Jump table.section.rodata.align 8.L4:.quad.L8 # x = 0.quad.L3 # x = 1.quad.L5 # x = 2.quad.L9 # x = 3.quad.L8 # x = 4.quad.L7 # x = 5.quad.L7 # x = 6 switch(x) { case 1: //.L3 w = y*z; case 2: //.L5 w = y/z; /* Fall Through */ case 3: //.L9 w += z; case 5: case 6: //.L7 w -= z; default: //.L8 w = 2; 5 Code Blocks long w = 1; switch(x) { case 1: //.L3 w = y*z; case 2: //.L5 w = y/z; /* Fall Through */ case 3: //.L9 w += z; case 5: case 6: //.L7 w -= z; default: //.L8 w = 2; return w; switch_eg: movq %rdx, %rcx cmpq $6, %rdi # x:6 ja.l8 # Use default jmp *.L4(,%rdi,8) # goto *JTab[x].L3: # Case 1 movq %rsi, %rax # y imulq %rdx, %rax # y*z ret.l5: # Case 2 movq %rsi, %rax cqto idivq %rcx # y/z jmp.l6 # goto merge.l9: # Case 3 movl $1, %eax # w = 1.L6: # merge: addq %rcx, %rax # w += z ret.l7: # Case 5,6 movl $1, %eax # w = 1 subq %rdx, %rax # w -= z ret.l8: # Default: movl $2, %eax # 2 ret 6

4 Procedure Call Registers Return %rax %eax %r8 %r8d Arg 5 %rbx %ebx %r9 %r9d Arg 6 Arg 4 %rcx %ecx %r10 %r10d Arg 3 %rdx %edx %r11 %r11d Arg 2 %rsi %esi %r12 %r12d Arg 1 %rdi %edi %r13 %r13d ptr %esp %r14 %r14d %ebp %r15 %r15d 7 Call Bo;om Increasing Addresses Pointer: Grows Down Top 8

5 Operations Bo8om Bo;om Increasing Addresses Increasing Addresses Pointer: -8 Grows Down Pointer: +8 Grows Down Top pushq Src Top popq Dest 9 Control Flow Example (1) <foo>: : callq <bar> : mov %rax,(%rbx) <bar>: : mov %rdi,%rax : retq 0x130 0x128 0x120 %rip 0x120 0x

6 Control Flow Example (2) <foo>: : callq <bar> : mov %rax,(%rbx) <bar>: : mov %rdi,%rax : retq 0x130 0x128 0x120 0x118 %rip 0x x118 0x Control Flow Example (3) <foo>: : callq <bar> : mov %rax,(%rbx) <bar>: : mov %rdi,%rax : retq 0x130 0x128 0x120 0x118 %rip 0x x118 0x

7 Control Flow Example (4) <foo>: : callq <bar> : mov %rax,(%rbx) 0x130 0x128 0x120 0x <bar>: : mov %rdi,%rax : retq %rip 0x Passing Data Registers First 6 arguments %rdi %rsi %rdx %rcx %r8 %r9 Return value %rax Arg n Arg 8 Arg 7 14

8 Frames Previous Frame Frame Pointer: (Op:onal) x Frame for proc Pointer: Top 15 Call Chain Example ( ) { (); ( ) { (); (); ( ) { (); Example Call Chain Procedure () is recursive 16

9 Frame Allocation (1) ( ) { (); 17 Frame Allocation (2) ( ) { ( ) { (); (); (); 18

10 Frame Allocation (3) ( ) { ( ) { ( ) (); (); { (); (); 19 Frame Allocation (4) ( ) { ( ) { ( ) (); (); { ( ) (); { (); (); 20

11 Frame Allocation (5) ( ) { ( ) { ( ) (); (); { ( ) (); { (); ( ) { (); (); 21 Frame Allocation (6) ( ) { ( ) { ( ) (); (); { ( ) (); { (); (); 22

12 Frame Allocation (7) ( ) { ( ) { ( ) (); (); { (); (); 23 Frame Allocation (8) ( ) { ( ) { (); (); (); 24

13 Frame Allocation (9) ( ) { ( ) { ( ) (); (); { (); (); 25 Frame Allocation (10) ( ) { ( ) { (); (); (); 26

14 Frame Allocation (11) ( ) { (); 27 Frame Components Frame pointer (Op<onal) pointer Caller Frame Arguments 7+ Return Addr Old Saved Registers + Local Variables Argument Build (Op<onal) 28

Assembly Programming IV

Assembly Programming IV CSE 351 Spring 2017 Instructor: Ruth Anderson Teaching Assistants: Dylan Johnson Kevin Bi Linxing Preston Jiang Cody Ohlsen Yufang Sun Joshua Curtis 1 Administrivia Homework 2 due