bolt/test/X86/split-func-jump-table-fragment-bidirection.s

   1 # This reproduces an issue where two fragments of same function access same
   2 # jump table, which means at least one fragment visits the other, i.e., one
   3 # of them has split jump table. As a result, all of them will be marked as
   4 # non-simple function.
   5
   6 # REQUIRES: system-linux
   7
   8 # RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown %s -o %t.o
   9 # RUN: llvm-strip --strip-unneeded %t.o
  10 # RUN: %clang %cflags %t.o -o %t.exe -Wl,-q
  11 # RUN: llvm-bolt -print-cfg -v=3 %t.exe -o %t.out 2>&1 | FileCheck %s
  12
  13 # CHECK: BOLT-INFO: Multiple fragments access same jump table: main; main.cold.1
  14 # CHECK: PIC Jump table JUMP_TABLE1 for function main, main.cold.1 at {{.*}}  with a total count of 0:
  15
  16   .text
  17   .globl main
  18   .type main, %function
  19   .p2align 2
  20 main:
  21 LBB0:
  22   andl $0xf, %ecx
  23   cmpb $0x4, %cl
  24   # exit through ret
  25   ja LBB3
  26
  27 # jump table dispatch, jumping to label indexed by val in %ecx
  28 LBB1:
  29   leaq JUMP_TABLE1(%rip), %r8
  30   movzbl %cl, %ecx
  31   movslq (%r8,%rcx,4), %rax
  32   addq %rax, %r8
  33   jmpq *%r8
  34
  35 LBB2:
  36   xorq %rax, %rax
  37 LBB3:
  38   addq $0x8, %rsp
  39   ret
  40 .size main, .-main
  41
  42 # cold fragment is only reachable
  43   .globl main.cold.1
  44   .type main.cold.1, %function
  45   .p2align 2
  46 main.cold.1:
  47   # load bearing nop: pad LBB8 so that it can't be treated
  48   # as __builtin_unreachable by analyzeJumpTable
  49   nop
  50 LBB4:
  51   andl $0xb, %ebx
  52   cmpb $0x1, %cl
  53   # exit through ret
  54   ja LBB7
  55
  56 # jump table dispatch, jumping to label indexed by val in %ecx
  57 LBB5:
  58   leaq JUMP_TABLE1(%rip), %r8
  59   movzbl %cl, %ecx
  60   movslq (%r8,%rcx,4), %rax
  61   addq %rax, %r8
  62   jmpq *%r8
  63
  64 LBB6:
  65   xorq %rax, %rax
  66 LBB7:
  67   addq $0x8, %rsp
  68   ret
  69 LBB8:
  70   callq abort
  71 .size main.cold.1, .-main.cold.1
  72
  73   .rodata
  74 # jmp table, entries must be R_X86_64_PC32 relocs
  75   .globl JUMP_TABLE1
  76 JUMP_TABLE1:
  77   .long LBB2-JUMP_TABLE1
  78   .long LBB3-JUMP_TABLE1
  79   .long LBB8-JUMP_TABLE1
  80   .long LBB6-JUMP_TABLE1
  81   .long LBB7-JUMP_TABLE1