[PATCH] D61524: [BPF] Support for compile once and run everywhere

[Yonghong Song via Phabricator via llvm-commits]

yonghong-song added a comment.

My current implementation has an issue like below:

For the intrinsic call,

  @0 = private unnamed_addr constant [8 x i8] c"sk_buff\00", align 1
  ...
    %4 = tail call %struct.anon* @llvm.preserve.di.access.index.p0s_struct.anons.p0s_struct.anons.p0s_struct.sk_buffs(%struct.anon* nonnull %3, %struct.sk_buff* %0, i8* getelementptr inbounds ([8 x i8], [8 x i8]* @0, i64 0, i64 0), i32 1), !dbg !43

The third argument `i8* getelementptr inbounds ([8 x i8], [8 x i8]* @0, i64 0, i64 0)` is constructed with `CreateGlobalStringPtr` which uses GEP internally.

For a test example, if I am using the clang directly to generate .s, everything is okay. But if I am using llc on IR instead, I hit a verification error.

  -bash-4.4$ clang -target bpf -O2 -g -Xclang -target-feature -Xclang +offsetreloc -S struct.c                                                 
  -bash-4.4$ clang -target bpf -O2 -g -Xclang -target-feature -Xclang +offsetreloc -S -emit-llvm struct.c
  -bash-4.4$ llc -march=bpfel -filetype=asm -mattr=offsetreloc struct.ll
  Global is referenced by parentless instruction!
  [8 x i8]* @0
  ; ModuleID = 'struct.ll'
    <badref> = getelementptr inbounds [8 x i8], [8 x i8]* @0, i64 0, i64 0
  Global is referenced by parentless instruction!
  [1 x i8]* @1
  ; ModuleID = 'struct.ll'
    <badref> = getelementptr inbounds [1 x i8], [1 x i8]* @1, i64 0, i64 0
  Global is referenced by parentless instruction!
  [1 x i8]* @1
  ; ModuleID = 'struct.ll'
    <badref> = getelementptr inbounds [1 x i8], [1 x i8]* @1, i64 0, i64 0
  LLVM ERROR: Broken module found, compilation aborted!
  -bash-4.4$

This could be related to my code below

  Call->replaceAllUsesWith(Call->getArgOperand(0));
  Call->eraseFromParent();

But I do not understand why it works with clang alone and fails with clang/llc.

Have anybody seen similar issues?


Repository:
  rL LLVM

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  https://reviews.llvm.org/D61524/new/

https://reviews.llvm.org/D61524