[PATCH] D61584: [DebugInfo] Some fields do not need relocations even relax is enabled.

Mon May 6 22:58:52 PDT 2019

HsiangKai added a comment.

In D61584#1491778 <https://reviews.llvm.org/D61584#1491778>, @probinson wrote:

> I don't claim to be an MCExpr expert, but I think this should not be necessary.  There are other situations where symbol differences are computed and emitted as constants, for example when DW_AT_high_pc is a length rather than an address, and they clearly don't require this tactic.

This patch is provided for the issue discussed in https://reviews.llvm.org/D45181#1470143.
When relaxation is enabled, linker may modify the code sequence according to relocation types. So, DW_AT_high_pc will be changed even it is used as a length instead of an address.

In current implementation, LLVM will generate relocations for ALL binary expressions if relaxation is enabled. However, not all binary expressions need relocations even relaxation is enabled. This attributes in MCExpr is designed for the values which are not expected to be changed after relaxation.

If the flag in MCExpr is an acceptable way to solve the problem, I will refine the patch, e.g., add test cases, until it is ready to land.

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D61584/new/

https://reviews.llvm.org/D61584