[PATCH] D77021: [Hexagon] R_HEX_GD_PLT_B22_PCREL cannot be relaxed.

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added a comment.

OK, I kinda understand the scheme now. Suggest renaming and replacing the test:

  % cat /tmp/c/hexagon-tls-gd-nonpreemptible.s
  # REQUIRES: hexagon                                                                                                                                   
  # RUN: llvm-mc -filetype=obj -triple=hexagon-unknown-elf %s -o %t.o        
  # RUN: ld.lld -shared %t.o -o %t.so  
  # RUN: llvm-readobj -r %t.so | FileCheck --check-prefix=RELOC %s
  # RUN: llvm-objdump -d --no-show-raw-insn --print-imm-hex %t.so | FileCheck %s
                                                                             
  ## Prior to D77021 lld would error "relocation R_HEX_GD_PLT_B22_PCREL cannot refer to absolute symbol".
  ## A PC-relative relocation referencing a non-preemptible absolute symbol (due to STT_TLS) is not representable in -pie/-shared mode.
  ## For this case we will actually patch the symbol to the external __tls_get_addr which is preemptible.
                                                                             
  .globl _start                                                              
  .type _start, @function                                                    
                                                                             
  # RELOC:      Section ({{.*}}) .rela.plt {  
  # RELOC-NEXT:   R_HEX_JMP_SLOT - 0x0                                       
  # RELOC-NEXT:   R_HEX_JMP_SLOT __tls_get_addr 0x0                  
  # RELOC-NEXT: }                    
                                                                             
  # CHECK:      { immext(#{{.*}})                                                                                                                       
  # CHECK-NEXT:   r2 = add(pc,##{{.*}}) }                                    
  # CHECK-NEXT: { immext(#{{.*}})                                                                                                                       
  # CHECK-NEXT:   r0 = add(r2,##-{{.*}}) }                                                                                                              
  # CHECK-NEXT: { call {{.*}} }                                                                                                                         
  # CHECK-NEXT: { r0 = memw(r0+#0x0) } 
                                       
  _start:                
    r2 = add(pc,##_GLOBAL_OFFSET_TABLE_ at PCREL)
    r0 = add(r2,##a at GDGOT)
    call a at GDPLT
    r0 = memw(r0+#0)
  
  ## a is non-preemptible due to STV_HIDDEN visibility.
  ## We can achieve the same effect with -Bsymbolic.
  .section        .tdata,"awT", at progbits
  .globl  a
  .hidden a
  a:
  .word 1

and updating the git description accordingly.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D77021/new/

https://reviews.llvm.org/D77021