| Issue |
91648
|
| Summary |
[BOLT] Support PIC fixed branch
|
| Labels |
BOLT
|
| Assignees |
|
| Reporter |
aaupov
|
[bolt-x86_64-ubuntu-clang](https://lab.llvm.org/buildbot/#/builders/252) started to fail with jump table heuristic failure (https://lab.llvm.org/buildbot/#/builders/252/builds/9615).
The crash is caused by the following function in GCC-built Clang:
_ZN5clang15ModuleMapParser23parseOptionalAttributesERNS_9ModuleMap10AttributesE.localalias
Unsupported code pattern is the following:
```
81a3a0f: 48 63 05 16 b4 03 fa movslq -0x5fc4bea(%rip), %rax # 0x21dee2c <CSWTCH.677+0x3dc>
81a3a16: 48 8d 15 03 b4 03 fa leaq -0x5fc4bfd(%rip), %rdx # 0x21dee20 <CSWTCH.677+0x3d0>
81a3a1d: 48 01 d0 addq %rdx, %rax
81a3a20: 3e ff e0 jmpq *%rax
```
The compiler could have avoided using PIC jump table access pattern and instead jump to the target directly. But since it has not, we need to gracefully handle that.
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