bolt/test/X86/shrinkwrapping-restore-position.s

   1 ## This checks that shrink wrapping uses the red zone defined in the X86 ABI by
   2 ## placing restores that access elements already deallocated by the stack.
   3
   4 # REQUIRES: system-linux
   5
   6 # RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown \
   7 # RUN:   %s -o %t.o
   8 # RUN: link_fdata %s %t.o %t.fdata
   9 # RUN: llvm-strip --strip-unneeded %t.o
  10 # RUN: %clang %cflags %t.o -o %t.exe -Wl,-q -nostdlib
  11 # RUN: llvm-bolt -relocs %t.exe -o %t.out -data %t.fdata \
  12 # RUN:     -frame-opt=all -simplify-conditional-tail-calls=false \
  13 # RUN:     -experimental-shrink-wrapping \
  14 # RUN:     -eliminate-unreachable=false | FileCheck %s
  15 # RUN: llvm-objdump -d %t.out --print-imm-hex | \
  16 # RUN:   FileCheck --check-prefix CHECK-OBJDUMP %s
  17
  18
  19 ## Here we create a CFG where the restore position matches the previous (deleted)
  20 ## restore position. Shrink wrapping then will put a stack access to an element
  21 ## that was deallocated at the previously deleted POP, which falls in the red
  22 ## zone and should be safe for X86 Linux ABI.
  23   .globl _start
  24   .type _start, %function
  25 _start:
  26   .cfi_startproc
  27 # FDATA: 0 [unknown] 0 1 _start 0 0 1
  28   push  %rbp
  29   mov   %rsp, %rbp
  30   push  %rbx
  31   push  %r14
  32   subq  $0x20, %rsp
  33 b:  je  hot_path
  34 # FDATA: 1 _start #b# 1 _start #hot_path# 0 1
  35 cold_path:
  36   mov %r14, %rdi
  37   mov %rbx, %rdi
  38   movq rel(%rip), %rdi  # Add this to create a relocation and run bolt w/ relocs
  39   leaq -0x20(%rbp), %r14
  40   movq -0x20(%rbp), %rdi
  41   leaq -0x10(%rbp), %rsp
  42   pop %r14
  43   pop %rbx
  44   pop %rbp
  45   ret
  46 hot_path:
  47   addq  $0x20, %rsp
  48   pop %r14
  49   pop %rbx
  50   pop %rbp
  51   ret
  52   .cfi_endproc
  53 end:
  54   .size _start, .-_start
  55
  56   .data
  57 rel:  .quad end
  58
  59 # CHECK:   BOLT-INFO: Shrink wrapping moved 2 spills inserting load/stores and 0 spills inserting push/pops
  60
  61 # CHECK-OBJDUMP:     <_start>:
  62 # CHECK-OBJDUMP:         leaq    (%rbp), %rsp
  63 # CHECK-OBJDUMP-NEXT:    popq    %rbp
  64 # CHECK-OBJDUMP-NEXT:    movq    -0x10(%rsp), %rbx
  65 # CHECK-OBJDUMP-NEXT:    movq    -0x18(%rsp), %r14
  66 # CHECK-OBJDUMP-NEXT:    retq