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Add base relative relocation record that can be used for the following case (OpenCL example):

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static __global int Var = 0; 
__global int* Ptr[] = {&Var};
...

In this case Var is a non premptable symbol and so its address can be used as the value of Ptr, with a base relative relocation that will add the delta between the ELF address and the actual load address. Such relocations do not require a symbol.

Differential Revision: https://reviews.llvm.org/D38909

llvm-svn: 315935
This commit is contained in:
Tony Tye 2017-10-16 20:44:29 +00:00
parent 8b8004661c
commit 9d875a6ad4
3 changed files with 13 additions and 1 deletions
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9
docs/AMDGPUUsage.rst
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@ -684,7 +684,12 @@ Following notations are used for specifying relocation calculations:
**S**
Represents the value of the symbol whose index resides in the relocation
entry.
entry. Relocations not using this must specify a symbol index of ``STN_UNDEF``.
**B**
Represents the base address of a loaded executable or shared object which is
the difference between the ELF address and the actual load address. Relocations
using this are only valid in executable or shared objects.
The following relocation types are supported:
@ -706,6 +711,8 @@ The following relocation types are supported:
``R_AMDGPU_GOTPCREL32_HI`` 9 ``word32`` (G + GOT + A - P) >> 32
``R_AMDGPU_REL32_LO`` 10 ``word32`` (S + A - P) & 0xFFFFFFFF
``R_AMDGPU_REL32_HI`` 11 ``word32`` (S + A - P) >> 32
*reserved* 12
``R_AMDGPU_RELATIVE64`` 13 ``word64`` B + A
========================== ===== ========== ==============================
.. _amdgpu-dwarf:

1
include/llvm/BinaryFormat/ELFRelocs/AMDGPU.def
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@ -14,3 +14,4 @@ ELF_RELOC(R_AMDGPU_GOTPCREL32_LO, 8)
ELF_RELOC(R_AMDGPU_GOTPCREL32_HI, 9)
ELF_RELOC(R_AMDGPU_REL32_LO, 10)
ELF_RELOC(R_AMDGPU_REL32_HI, 11)
ELF_RELOC(R_AMDGPU_RELATIVE64, 13)

4
test/Object/AMDGPU/elf64-relocs.yaml
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@ -15,6 +15,7 @@
# CHECK: 0x18 R_AMDGPU_GOTPCREL32_HI - 0x0
# CHECK: 0x20 R_AMDGPU_REL32_LO - 0x0
# CHECK: 0x22 R_AMDGPU_REL32_HI - 0x0
# CHECK: 0x24 R_AMDGPU_RELATIVE64 - 0x0
# CHECK: }
# CHECK: ]
@ -72,6 +73,9 @@ Sections:
- Offset: 0x22
Symbol: s11
Type: R_AMDGPU_REL32_HI
- Offset: 0x24
Symbol: s12
Type: R_AMDGPU_RELATIVE64
Symbols:
Local: