| commit | bb03cdcb441fd68da9d1ebb7d5f39f73667cd39c | [log] [tgz] |
|---|---|---|
| author | Fangrui Song <i@maskray.me> | Fri May 23 18:44:15 2025 -0700 |
| committer | GitHub <noreply@github.com> | Fri May 23 18:44:15 2025 -0700 |
| tree | 27d76f4d725a8b0a1cc8eb3f9d7ca9fcc3a2a4b0 | |
| parent | d5802c30ae6cf296489daf12b36582e9e1d658bb [diff] |
RISCV: Remove shouldForceRelocation and unneeded relocations Follow-up to #140494 `shouldForceRelocation` is conservative and produces redundant relocations. For example, RISCVAsmBackend::ForceRelocs (introduced to support mixed relax/norelax code) leads to redundant relocations in the following example adapted from #77436 ``` .option norelax j label // For assembly input, RISCVAsmParser::ParseInstruction sets ForceRelocs (https://reviews.llvm.org/D46423). // For direct object emission, RISCVELFStreamer sets ForceRelocs (#77436) .option relax call foo // linker-relaxable .option norelax j label // redundant relocation due to ForceRelocs .option relax label: ``` Root problem: The `isSymbolRefDifferenceFullyResolvedImpl` condition in MCAssembler::evaluateFixup does not check whether two locations are separated by a fragment whose size can be indeterminate due to linker instruction (e.g. MCDataFragment with relaxation, or MCAlignFragment due to indeterminate start offst). This patch * Updates the fragment walk code in `attemptToFoldSymbolOffsetDifference` to treat MCRelaxableFragment (for --riscv-asm-relax-branches) as fixed size after finishLayout. * Adds a condition in `addReloc` to complement `isSymbolRefDifferenceFullyResolvedImpl`. * Removes the no longer needed `shouldForceRelocation`. This fragment walk code path handles nicely handles mixed relax/norelax case from https://discourse.llvm.org/t/possible-problem-related-to-subtarget-usage/75283 and allows us to remove `MCSubtargetInfo` argument (#73721) as a follow-up. This fragment walk code should be avoided in the absence of linker-relaxable fragments within the current section. Adjust two bolt/test/RISCV tests (#141310) Pull Request: https://github.com/llvm/llvm-project/pull/140692
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