fedor.sergeev added a comment. In D70157#1775016 <https://reviews.llvm.org/D70157#1775016>, @annita.zhang wrote:
> > The point is that we have explicit requirement at the start and we have a > > lowering into 16-byte sequence that we need to be preserved exactly as it > > is. > > Essentially what we need is a "protection" for this sequence from any > > changes by machinery that generates the binary code. > > How can we protect a particular byte sequence from being changed by this > > branch aligner? > > No, in general we can't. The current solution is based on assembler to insert > prefix or nop before the cross (or against) boundary branches. It can only > ensure the explicit alignment specified by directive, but not any implicit > alignment. I don't think any fixup based on assembler can do it. On the other > hand, any code sequence after the alignment directive or even just in a > function has some kind of implicit alignment. It's hard for assembler to tell > which implicit alignment to preserve. The preferred way is to use explicit > alignment directive to specify it. > > For your scenario, a NOP padding is more controllable. NOP padding will be > inserted just before the branch instructions (or macro fusion branch > instructions). So if there's no branches (or macro fusion branches) in your > code sequence, there will be no NOP inserted. What if I insert explicit align(8) right *after* the sequence? CHANGES SINCE LAST ACTION https://reviews.llvm.org/D70157/new/ https://reviews.llvm.org/D70157 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
