Thanks, that's better. The clang front-end option is not directly relevant for the semantic of the intrinsic, so it would be better to explicitly specify it was not being fuseable unless the operand degenerates into a single operand. Otherwise the specification sounds reasonable.

Please make sure at the very least that it doesn't get matched if a function named strlen and also test for that.

We inherited the lack of int128_t support on 32bit platforms from GCC. IMO we should fix that, the only tricky one is division.

One of the mots important use cases of __builtin_constant_p is ensuring that inline assembler variants that require immediate arguments are DCE'ed. There are some other use cases where it is used for compile-time assertions of invariants, so we do want to be as correct as possible. All that said, I fully agree that is.constant(undef) should fold to false as it is consistent with the immarg parameter attribute and other places. Even stronger, I would argue that it applies even to is.constant(freeze undef).

There are two approaches that work for reviewing: starting from clang and going down or starting from compiler-rt and going up the layers. I'd prefer to do the latter as it means meaningful testing can be done easier. There are two natural steps here: clang flag+IR generation is one, llvm codegen and compiler-rt is the other. The clang step should include tests that ensure that proper IR is generated for the different flag combination (including documentation for the IR changes). The LLVM step should ensure that the different attributes (either function or module scope) are correctly lowered in the instrumentation pass and unit tests on the compiler-rt side to do functional testing. The unit testing might also be done as a third step if it goes the full way from C to binary code.

This review doesn't make sense to me. Why add a flag that isn't affecting anything? Why add a flag that isn't even tested?

"Keeping the original spelling around" would assume that the input is not using a stateful encoding. That seems worse as assumption than giving the canonical output in UTF-8 and shifting the problem to the user's editor?

This sounds wrong. If you are using 'x86_64-freebsd' as triple and -m32, it should still call 'x86_64-freebsd-ld', but it is the responsibility of the driver to ensure that also the right set of linker flags are passed as well. Compare netbsd::Linker::ConstructJob for one way to handle this.

Yeah, I hit a compilation error somewhere depending on the include error. I forgot the details, this has been sitting around in my tree for while.

The NetBSD part looks ok, but also lacks proper testing. I'm not sure anyone but Linux cares at all otherwise as they lack 32bit SPARC support.

That covers my case. I'm not completely happy with the need to rethrow, but the alternatives are much worse. It's a bit sad that we can't optimize it away, too.

Resummited

Registers_arm64::jumpto in UnwindRegistersRestore.S.

Let me rephrase then. The restore code explicitly ends in "ret x30". It cannot set "pc" separate from "x30" in the current form. I'm not saying that the DWARF register shouldn't be supported, but this change doesn't do that.

I don't get this change. The restore code is literally returning by jumping to x30, so how is splitting PC and LR supposed to work?

The test case needs to be resorted, so that the DOTEXPR test comes last, but otherwise this change works for me.

I have one concern about sparc-relocations.s, but that is not specific to the change at hand. IMO we should also have a variant of all the relocations with a fixed values of sym to test that the right bits are actually set. That would also make comparing the fixup handling easier e.g. to GNU as.

I can't speak for other systems, but forcing libpthread to be linked is in general not desirable as it creates a non-trivial runtime cost, especially when <thread> is not used. That's still a pretty common use case of C++.

The NetBSD part is most definitely not acceptable.

First of all, I find this patch to be nearly impossible to read. It seems to mix a lot of refactoring with a functional change, making it very hard to focus on the core.

It might be specific to the jump table case, but it should be instructional on how to do it. One important point is that it avoids inter-section relocations, which are a problem at least on MIPS.

Some targets already do this. Please check that you don't create regressions, especially on PowerPC.

off_t is s signed type. Please fix the description.

Do we really want to change the code here? It is perfectly well defined behavior.

The difference is whether we promise to be instruction precise or not. I'm not sure we do or want to promise that as default.

I have no problem with the change, but please adjust the description to take about -funwind-tables. I don't think we do async by default, at least not by design.

"It compiles with GCC" is not really helpful as argument because the observed behavior depends on a lot of internals. It is quite frankly impossible to be 100% identical to GCC's behavior. What LLVM guarantees is:
(1) Folding to false happens as late as reasonable possible. It happens most importantly after the first round of function and loop optimizations.
(2) Folding to true happens as part of constant folding etc as early as the condition is evaluated.
(3) The result is propagated to derived expression and those are folded recursively, including dead code elimination. This happens even for -O0.

I completely agree with Roman that this patch is very undesirable since it has a high chance of breaking other reasonable uses of the intrinsic. In fact, I would say that the observed behavior here is perfectly reasonable under the definition of @lllvm.is.constant. The original code for LLVM at least should be just __builtin_constant_p(b) && b > -129 && b < 128).

You can do an anon-mapping with size+pagesize in that case and map over it with MAP_FIXED.

Disabling builtin handling when asm is enabled would be a major annoyance for NetBSD. The interaction between symbol renaming and TLI is complicated. There are cases where it would make perfect sense and others were it would be harmful. Example of the latter is the way SSP is implemented by inline functions that call a prototype renamed back to the original symbol name.

I'm still curious about the source of the vptr diff, but that's a minor question, otherwise. LGTM

I don't think this is the right place for this at all. Look at X86Subtarget::initSubtargetFeatures please.

Can you change raw_fd_ostream::has_colors to memoize the result of FileDescriptorHasColors(FD) instead? That should give most of the performance gain without breaking the abstractions as much.

This issue is on my long term TODO list. If there are no 64bit atomics, it is a really stupid idea to use them for timekeeping. I think for the use case of Timer, just splitting it into second and subsecond with explicit overflow handling is perfectly reasonable and does not affect the correctness of the normal use as the aggregates are only accessed on completion?

Please don't change the style of the code, it messes up review and the full source. Please split the introduction and testing of the new relocation into one patch and using a different set of relocations to implement large code model. The latter part needs at least a test as well?

I don't agree with the justification at all, but it also seems that noone else cares about the build option creep here.

I see that more as a short-coming in the existing DEFAULT_SYSROOT behavior and less an argument for making more cases like it. So the general idea is that for turnkey toolchains,
we want to allow customizing the "default" target of the toolchain to hard-code options like --sysroot, --target, -Wl,-rpath etc. Those are all related, so when using a different target, they no longer make sense. One way to deal with all those options in a consistent manner is hook into the logic for determining the current target, if none is explicitly specified on the command line or implicit from the executable name, then prepend some additional flags on the command line based on some cmake variable or so. This flags shouldn't trigger the unused argument warnings, so you can always pass -Wl,-rpath, --sysroot etc, independent of whether the compiler is in preprocessing / compile / assemble / link mode. That seems to be a more general and systematic approach than adding many additional build-time options.

I do agree with the feature request, but I'm not sure about the implementation. It doesn't seem to work well with the cross-compiling support in the driver as clearly shown by the amount of tests that need patching. Is cross-compiling a concern for you at all? Otherwise I would suggest going a slightly different route and use default values iff no "-target" or "target-command" mechanism is active. Might need a way to temporarily disable unused flag warnings, but that way would be pretty much toolchain independent?

LGTM

ARM's data detection only works for unstripped binaries. Other architectures often don't even have such markers at all.

The more compact output is a lot harder to read when you have to find embedded data. I wouldn't mind dropping half the spaces to have columns of 4 hex digits, but anything more is really hard to read.

I'm not sure about this change. It might make sense on x86, but many RISC architectures love to put data into the instruction stream and being able to pick them out is quite important for understanding the disassembly.

LGTM

@ldionne I was updating libc++ from d42baff45d9700a199982ba0ac04dbc6c6d911bb and LLVM itself from 38aebe5c04ab4cb3695dc1bcc60b9a7b55215aff to 3d1424bc7a0e9a6f9887727e2bc93a10f50e1709 when it started failing. It likely has been present for a while.

This fixes the module build of clang for me.

If no (inline) assembler is involved, you can likely get away with IAS. Just to give two trivial examples that are not handled by IAS right now:

Louis, did I answer your questions?

We tend to test push .section and .pushsection in this file, so it would be nice to continue doing that.

Can you add a variation with .pushsection for @progbits and @nobits? Otherwise LGTM.

Ping?

This summarizes the IRC discussion.

The original code has a functional dependency between sz and bytes and whether they can be constant evaluated. But the code doesn't express that. I don't think we can enforce that in any sensible way. There are valid use cases after all where partial inlining would result in entirely sensible decisions, just think about the more typical case of __builtin_constant_p selecting between inline asm taking immediate operands and one taking register/memory operands. That's why I am saying that I consider it a lot more useful to provide reliable building blocks to express the dependency and make sure they work.

...in the outer condition, I meant.

Yes, builtin_expect is just noise here. The point I wanted to make is that both sz and bytes should be used in builtin_constant_p in the other condition.

IMO the root of the problem here is that the branches are mixing predicated variables (bytes) with non-predicated variables (sz). If users want deterministic behavior here, that shouldn't be done.

I was discussing this with Bill off-list to get a better idea of the original test case. Basically, with the new constant intrinsic pass, we can provide a stronger semantic: the default LLVM pass chain always constant folds expressions involving is.constant and performs DCE trivially dead branches resulting from the former folding. This means that if the original expression is adjusted from:

if (__builtin_expect(!!(sz >= 0 && sz < bytes), 0)) {
    if (!__builtin_constant_p(bytes))
    ...
}

to the functionally equivalent:

if (!(__builtin_constant_p(sz) && __builtin_constant_p(bytes) && sz >= 0 && sz >= bytes) && __builtin_expect(!!(sz >= 0 && sz < bytes), 0)) {
    if (!__builtin_constant_p(bytes))
    ...
}

then we can actually ensure proper DCE even with -O0 in the default pass chain. That depends over all on two properties:

• If __builtin_constant_p is constant folded by clang, it must DCE the appropiate places.
• the constant intrinsic pass is run

With -O1 or higher, this should work in general.

Committed as 0b999f76575f0196d3cd01c0781b2513b0a1af15 without link.

Require __STDCPP_NEW_ALIGNMENT__ in C++03 mode. Prefer it over max_align_t in a number of tests when allocation alignment is desired. Adjust some tests to do minimal sanity checking of the alignment for C++03 only. Add an explicit check that __STDCPP_NEW_ALIGNMENT__ is more general than max_align_t if both are present.

This looks much better than the in-tree state, thanks.