rjmccall added inline comments.
================ Comment at: clang/include/clang/Basic/LangOptions.h:394 + return true; + } + ---------------- sepavloff wrote: > erichkeane wrote: > > rjmccall wrote: > > > erichkeane wrote: > > > > rjmccall wrote: > > > > > rjmccall wrote: > > > > > > erichkeane wrote: > > > > > > > rjmccall wrote: > > > > > > > > The problem with having both functions that take `ASTContext`s > > > > > > > > and functions that don't is that it's easy to mix them, so they > > > > > > > > either need to have the same behavior (in which case it's > > > > > > > > pointless to have an overload that takes the `ASTContext`) or > > > > > > > > you're making something really error-prone. > > > > > > > > > > > > > > > > I would feel a lot more confident that you were designing and > > > > > > > > using these APIs correctly if you actually took advantage of > > > > > > > > the ability to not store trailing FPOptions in some case, like > > > > > > > > when they match the global settings in the ASTContext. That > > > > > > > > way you'll actually be verifying that everything behaves > > > > > > > > correctly if nodes don't store FPOptions. If you do that, I > > > > > > > > think you'll see my point about not having all these > > > > > > > > easily-confusable functions that do or do not take > > > > > > > > `ASTContext`s.. > > > > > > > I think I disagree with @rjmccall that these > > > > > > > requiresTrailingStorage should be here at all. I think we should > > > > > > > store in the AST ANY programmer opinion, even if they match the > > > > > > > global setting. It seems to me that this would be more tolerant > > > > > > > of any global-setting rewrites that modules/et-al introduce, as > > > > > > > well as make the AST Print consistent. Always storing FPOptions > > > > > > > when the user has explicitly overriding it also better captures > > > > > > > the programmer's intent. > > > > > > I covered this elsewhere in the review. If you want to have that > > > > > > tolerance — and I think you should — then expressions should store > > > > > > (and Sema should track) the active pragma state, which can be most > > > > > > easily expressed as a pair of an FPOptions and a mask to apply to > > > > > > the global FPOptions. When you enter a pragma, you clear the > > > > > > relevant bits from the global FPOptions mask. > > > > > > > > > > > > But the whole point of putting this stuff in trailing storage is so > > > > > > that you can make FPOptions as big as you need without actually > > > > > > inflating the AST size for a million nodes that don't care in the > > > > > > slightest about FPOptions. > > > > > > But the whole point of putting this stuff in trailing storage is so > > > > > > that you can make FPOptions as big as you need without actually > > > > > > inflating the AST size for a million nodes that don't care in the > > > > > > slightest about FPOptions. > > > > > > > > > > I meant to say: for a million nodes that don't care in the slightest > > > > > about FPOptions, as well as for a million more nodes that aren't > > > > > using pragma overrides. > > > > Right, I get the intent, and I completely agree with that. My point > > > > was EVERY Expr that is affected by a #pragma should store it. Though, > > > > after looking at your Macro concern above, I'm less compelled. > > > > > > > > I guess was suggesting that the logic for "requiresTrailingStorage" > > > > should just be "modified by a pragma" instead of "FPOptions != The > > > > global setting". > > > Well, "modified by a pragma" still wouldn't make the AST agnostic to > > > global settings, since the pragmas don't override everything in FPOptions > > > at once. But I agree that would achieve the most important goal, which > > > is to stop inflating the AST when pragmas *aren't* in effect, which is > > > approximately 100% of the time. In order to do that, though, we'll need > > > to start tracking pragmas, which we should do but which can wait for a > > > follow-up patch. In the meantime, I don't think you're ever going to get > > > the interfaces right for queries like `BinaryOperator::getFPOptions` > > > unless you actually stop relying on the fact that you're unconditionally > > > storing `FPOptions`. You need to passing around ASTContexts for that. > > > That's why I'm suggesting using an exact match with the global settings > > > as a simple thing you can easily check without modifying what data you > > > collect in `FPOptions`. > > That sounds like a good plan to me. Thanks for entertaining my > > conversation/questions. > > we'll need to start tracking pragmas > > This is made in D76599 by representing floating point pragmas with a special > statement node. These nodes allow an AST consumer like CodeGen or constant > evaluator to maintain current set of floating options when it traverses AST. > This approach looks simpler and more consistent as global state is > represented as a variable in AST consumer and is not replicated to every > relevant node. It makes easier to implement codegen for things like rounding > mode, when change of the FP state requires specific instructions. A pragma > statement can be used to generate required code. But if the state is spread > by several nodes, it is more difficult for codegen to create necessary > prolog/epilog code. Now compiler does not have support of properties that > need synchronization with hardware, so these problems are not topical yet, > but they eventually will arise. Constant evaluation does not normally traverse the AST in the way you mean. It does this when evaluating a constexpr function, but that's not the dominant case of constant evaluation. At the LLVM level, I think inlining, reordering, and ABI requirements on calls argue against a simple implementation model based on setting hardware flags when a pragma is entered and resetting them on exit. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D76384/new/ https://reviews.llvm.org/D76384 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
