MaskRay added a comment. In D85408#2253073 <https://reviews.llvm.org/D85408#2253073>, @tmsriram wrote:
> In D85408#2253055 <https://reviews.llvm.org/D85408#2253055>, @MaskRay wrote: > >> I am still reading the patch, but I have noticed one thing worth discussing. >> `.bb_addr_map` is a non-SHF_ALLOC section (meaning that it is not part of >> the memory image). An absolute relocation type (`.quad >> .Lfunc_begin0`) works but the value is a link-time address, not taking >> account of the load base (PIE/shared object)). (If .bb_addr_map has the >> SHF_ALLOC flag, linkers will report a text relocation) How do you intend to >> use `.bb_addr_map` at runtime? > > bb_addr_map is intentionally not loaded as it is never meant to be used at > run-time. bb_addr_map will be later be used in conjunction with a hardware > profile of the binary to associate executed basic block addresses to machine > basic blocks. The hardware profile of the binary has enough info to > determine the load base address with PIE, this is pretty straight forward and > multiple strategies exist. What exactly is the concern here? Thanks for the explanation! I guessed that non-SHF_ALLOC is intended but hoped that it can confirmed (and you did!). This sections works similar to `.stack_sizes` emitted by clang -fstack-size-section. This is important because for SHF_ALLOC, SHF_WRITE is also needed to avoid text relocations. I am still reading the patch to ensure that it will work as intended. ================ Comment at: llvm/test/CodeGen/X86/basic-block-sections-labels-functions-sections.ll:21 +; CHECK: .section .text._Z3foov,"ax",@progbits +; CHECK-LABEL: _Z3foov: +; CHECK-NEXT: [[FOO_BEGIN:.Lfunc_begin[0-9]+]]: ---------------- Consider align the content. Since `CHECK-LABEL:` is the longest. ``` ; CHECK: .section .text._Z3foov,"ax",@progbits ; CHECK-LABEL: _Z3foov: ; CHECK-NEXT: [[FOO_BEGIN:.Lfunc_begin[0-9]+]]: ``` Non-labels have additional indentation to make it clear they are bodies covered by labels. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D85408/new/ https://reviews.llvm.org/D85408 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
