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llvm-project/bolt/test/X86/zero-sized-object.s

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[BOLT] Fix false references to zero-sized objects Summary: Whenever BOLT encounters a data reference in code, it tries to convert it into <Object+Offset> form. The primary reason behind this approach is to support read-only data-reordering optimization. However, with the current level of the linker and compiler support we don't have enough information to always correctly restore the original <Object+Offset>. E.g. with zero-sized symbols we have to speculate that the actual size of the underlying object extends to the next symbol. Most of the time, there will be an object pointed by a zero-sized symbol and even if we are guessing incorrectly, there will be no harm in creating references of such form. The problem happens when there's no object corresponding to the original symbol and the next object is an (unmarked) jump table: A: # <- zero-sized object .LJUMP_TABLE: .long <entry1> .long <entry2> .... .LB: .long 21 .LC: .long 42 The jump table will be moved and all references past it (up to the next named object) will be incorrectly updated. We should not speculate about the size of A in a case like that and treat all discovered data objects (and thus references) independently. (cherry picked from FBD27005660)
2021-03-16 03:06:56 +08:00
# Check that references to local (unnamed) objects below are not
# treated as references relative to zero-sized A object.
# REQUIRES: system-linux
# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown \
# RUN: %s -o %t.o
[BOLT][TEST] Remove -no-pie from cflags/cxxflags Align with an upstream change D120305 to make PIE the default on linux-gnu. Add `-no-pie` to tests that require it. Reviewed By: maksfb, yota9 Differential Revision: https://reviews.llvm.org/D123329
2022-04-08 02:23:20 +08:00
# RUN: %clang %cflags -no-pie %t.o -o %t.exe -Wl,-q
[BOLT] Fix false references to zero-sized objects Summary: Whenever BOLT encounters a data reference in code, it tries to convert it into <Object+Offset> form. The primary reason behind this approach is to support read-only data-reordering optimization. However, with the current level of the linker and compiler support we don't have enough information to always correctly restore the original <Object+Offset>. E.g. with zero-sized symbols we have to speculate that the actual size of the underlying object extends to the next symbol. Most of the time, there will be an object pointed by a zero-sized symbol and even if we are guessing incorrectly, there will be no harm in creating references of such form. The problem happens when there's no object corresponding to the original symbol and the next object is an (unmarked) jump table: A: # <- zero-sized object .LJUMP_TABLE: .long <entry1> .long <entry2> .... .LB: .long 21 .LC: .long 42 The jump table will be moved and all references past it (up to the next named object) will be incorrectly updated. We should not speculate about the size of A in a case like that and treat all discovered data objects (and thus references) independently. (cherry picked from FBD27005660)
2021-03-16 03:06:56 +08:00
# RUN: llvm-bolt %t.exe -print-cfg \
# RUN: -print-only=main -o %t.out | FileCheck %s
.file "rust_bug.c"
.section .rodata
.LC0:
.string "0"
.LC1:
.string "1"
.LC2:
.string "2"
.LC3:
.string "3"
.LC4:
.string "4"
.LC5:
.string "5"
.text
.globl inc_dup
.type inc_dup, @function
inc_dup:
.LFB0:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset 6, -16
movq %rsp, %rbp
.cfi_def_cfa_register 6
subq $16, %rsp
movl %edi, -4(%rbp)
movl -4(%rbp), %eax
subl $10, %eax
cmpl $5, %eax
ja .L2
movl %eax, %eax
movq .L4(,%rax,8), %rax
jmp *%rax
.section .rodata
.align 8
.globl A
.type A, @object
A:
.section .rodata
.align 8
.align 4
.L4:
.quad .L3
.quad .L5
.quad .L6
.quad .L7
.quad .L8
.quad .L9
.text
.L3:
movl $.LC0, %edi
call puts
movl $1, %eax
jmp .L10
.L5:
movl $.LC1, %edi
call puts
movl $2, %eax
jmp .L10
.L6:
movl $.LC2, %edi
call puts
movl $3, %eax
jmp .L10
.L7:
movl $.LC3, %edi
call puts
movl $4, %eax
jmp .L10
.L8:
movl $.LC4, %edi
call puts
movl $5, %eax
jmp .L10
.L9:
movl $.LC5, %edi
call puts
movl $6, %eax
jmp .L10
.L2:
movl -4(%rbp), %eax
addl $1, %eax
.L10:
leave
.cfi_def_cfa 7, 8
ret
.cfi_endproc
.LFE0:
.size inc_dup, .-inc_dup
.section .rodata
.LC6:
.string "%d\n"
.text
.globl main
.type main, @function
main:
# CHECK: Binary Function "main" after building cfg
.LFB1:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset 6, -16
movq %rsp, %rbp
.cfi_def_cfa_register 6
movl .LN(%rip), %eax
# We should not reference a data object as an offset from A
# CHECK-NOT: movl A+{{.*}}(%rip), %eax
movl %eax, %esi
movl $.LC6, %edi
movl $0, %eax
call printf
movl $0, %eax
popq %rbp
.cfi_def_cfa 7, 8
ret
.cfi_endproc
.LFE1:
.size main, .-main
.section .rodata
.align 4
.LN:
.long 42
.ident "GCC: (GNU) 4.8.5 20150623 (Red Hat 4.8.5-44)"
.section .note.GNU-stack,"",@progbits