In generate_ast.cpp, an `CarbonExternalASTSource` is installed that has
a `Check::Context` pointer. During lowering, this `ExternalASTSource` is
still installed, and using it can cause a crash if the now-invalid
pointer is dereferenced.
Fix by adding a new `ReadOnlyASTSource` in sem_ir, and using that during
lowering.
`CarbonExternalASTSource` now inherits from `ReadOnlyASTSource` to avoid
some code duplication.
In generate_ast.cpp, we now always install a multiplex source, even if
there's only one child source. Clang internally keeps pointers to the
top-level `ExternalASTSource` installed via `setExternalSource`, and
those pointers aren't updated if `setExternalSource` is called again. By
using `MultiplexExternalSemaSource`, we can keep the top-level
`ExternalASTSource` pointer the same, and only update its children.
Using `MultiplexExternalSemaSource` this way requires a new constructor
and a method to modify its child sources; added a new LLVM patch adding
those.
https://github.com/carbon-language/carbon-lang/issues/7142
Fundamentally, this uses forward declarations of Clang types to reduce
the overall compile time cost of Clang headers across the codebase.
Tracing and profiling showed ~2s of every check TU's ~8-12s compile time
going just to parsing Clang frontend and AST headers pulled in via a few
sem_ir and check headers that only use the Clang types by pointer or
reference:
- sem_ir/cpp_file.h (reached via sem_ir/file.h by ~150 TUs) included
clang/Frontend/CompilerInstance.h, clang/CodeGen/ModuleBuilder.h,
clang/AST/Mangle.h, and llvm/IR/Module.h. CppFile's accessors move out
of line to a new cpp_file.cpp and the header now forward-declares the
Clang types.
- check/cpp/context.h (reached via check/context.h by ~100 TUs) included
clang/Frontend/FrontendAction.h and clang/Parse/Parser.h, pulling in
clang's Sema.h and ASTUnit.h.
- sem_ir/clang_decl.h included clang/AST/Decl.h; the three small
functions that need complete Clang types move out of line.
- sem_ir/cpp_overload_set.h included clang/Sema/Overload.h solely for
the three-field OverloadCandidateSet::OperatorRewriteInfo, which is now
mirrored as CppOverloadSet::OperatorRewriteInfo, and clang/AST/Decl.h
solely for a pointer.
- sem_ir/name_scope.h's clang/AST/DeclBase.h include was vestigial.
TUs (and more narrowly included headers) that genuinely use the Clang
definitions now include the Clang headers directly.
Representative compile times (fastbuild, aarch64), combined with the
preceding instantiation-cost changes, relative to trunk:
- check/eval.cpp: 11.85s -> 6.94s (-41%)
- check/handle_operator.cpp: 7.71s -> 3.30s (-57%)
- language_server.cpp: 6.68s -> 3.16s (-53%)
- lower/handle.cpp: 6.75s -> 3.66s (-46%)
- sem_ir/file.cpp: 8.60s -> 6.11s (-29%)
- driver.cpp: 6.68s -> 4.78s (-28%)
Measured full-rebuild impact (316 first-party TUs, fastbuild): -689.5s
CPU, -29.9% relative to trunk.
Assisted-by: Claude
The intent is to add visibility into how the fingerprint is computed, so
that fingerprinting issues and mangling collisions can be more readily
understood and fixed.
Assisted-by: Gemini via Antigravity
Instead of treating all C++ code as coming from a single synthetic
`CheckIRId`, track the `SemIR::File` associated with each C++ location.
This is necessary since each `SemIR::File` has a distinct `CppFile` and
therefore distinct `SourceLocation`s and `ClangSourceLocId`s.
Assisted-by: Gemini via Antigravity
Some module metadata changed - because rather than linking one module
with one module metadata value (eg: PIC Level 0, or unspecified) and one
module with a different one (PIC level 2, in clang) - we use Clang's
Module as-is, no merging required, so Clang's module metadata sticks
rather than being merged with default values from Carbon.
Also tweaked the name we use for Clang's module name so it matches the
carbon file name.
Otherwise the IR changes seem to be just reorderings - C++ interop goes
first, then Carbon, rather than the other way around.
This helps at least lldb handle calling functions (currently the debug
info describes every function as `void()`, so no parameters or return
values are supported) - seems gdb and lldb both depend on demangling to
varying degrees in C code (marking a function as "prototyped" in C in
DWARF does seem to also address this problem).
Given:
```
fn PrintThree() {
Core.Print(3);
}
```
Before:
```
(lldb) p PrintThree()
error: Couldn't look up symbols:
PrintThree
Hint: The expression tried to call a function that is not present in
the target, perhaps because it was optimized out by the compiler.
```
After:
```
(lldb) p PrintThree()
3
(lldb)
```
Adds a flag `--optimize=<mode>` that specifies what to optimize for:
* `--optimize=none` turns off the optimizer as much as possible, but
still respects always_inline.
* `--optimize=debug` aims to be the equivalent of `-Og` / `-O1`, and
provides optimizations that don't affect the ability to debug the
program. This is the default.
* `--optimize=size` optimizes for the size of the produced program, and
aims to be the equivalent of `-Oz`.
* `--optimize=speed` optimizes for the execution time of the produced
program, and aims to be the equivalent of `-O3`.
Following the approach taken by Clang, the optimization level feeds into
both the configuration of the LLVM pass pipeline and the attributes
added to function definitions generated by the frontend.
Optimization is performed in a new phase, `optimize`, which runs between
`lower` and `codegen`.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Now that the total number of IRs is available from SemIR::File, we can
use FixedSizeValueStore to store/look up values mapped from a CheckIRId
instead of a Map, which is demonstrably faster (unsurprisingly, since
it's just a vector index). See #6019.
This replaces a Map with FixedSizeValueStore in Lower::Context for use
in `GetFileContext()`. This function is used in some places that can
become hot, such as `HandleInst()` and `GetType()`. In our current
lowering tests, there's no measurable performance change from this PR,
but based on #6019 we can expect to see one as the amount of
instructions being lowered increases. Using a FixedSizeValueStore when
possible is a better approach than a map, generally.
This takes the debug runtime of
`toolchain/check/testdata/interop/cpp/function/arithmetic_types_bridged.carbon`
from 4.7s down to about 4s (so 15% faster overall).
There's still lots of room to improve this test which seems to be
hitting lots of pathological behaviour, but InstNamer is 30% of the
runtime, with fingerprinting's `InstFingerprinter::GetOrCompute`
consuming 10% of cycles. We reduce its impact by using a vector of
vectors instead of a Map for the cache of fingerprints. After this
change InstNamer drops below 24% of the runtime.
Also move the instruction name when giving it to `AllocateName` since it
receives std::string by value, though this doesn't show up in the
profile for the test.
This is trying to make it clearer when vectors are being indexed with
`CheckIRId`.
The only one that I still kind of want to change is the
`SmallVector<std::unique_ptr<CompilationUnit>>`, but because it's a
`unique_ptr` that's a little more complex. I may not bother.
Note, some of the changes around nuanced `SmallVector` interactions were
based on trying to copy the way `SmallVector` itself takes arguments,
like with range passing.
By moving dumping, we can have dumping occur before verification that
might CHECK-fail (e.g. parse tree and llvm IR verification).
I'm dropping vlogging of raw semir. It was only done when dumping, so
`-v` would print zero copies and `-v --dump-raw-sem-ir` would print two
copies. The lack of complaints about this suggests it's not needed.
I'm making a small change to drop newlines between textual and raw
semir. This is an edge case so I don't expect people to really notice in
general, but it seemed unusually aware of what's on a stream, and it
made it harder to do the dump_stream/raw_dump_stream approach, which I
felt would be decent in general, since check is the only phase that can
emit two different things (which I could also just drop -- we don't
really use raw semir anymore, it doesn't seem like a big need to be able
to print it with textual semir, but I'm assuming to just maintain
existing behavior).
In parse, we were previously dumping the tree on verification errors.
I'm removing that because now `--dump-parse-tree` should work fine,
where previously it wouldn't.
Suggested by zygoloid while looking at #5678
```
CHECK failure at toolchain/lower/context.cpp:62: !llvm::verifyModule(*llvm_module_, &errs): Verifier errors: Instruction does not dominate all uses!
%.loc17_46.1.temp = alloca { i1, i32, i32 }, align 8, !dbg !13
%tuple.elem0.loc17_46.2.tuple.elem = getelementptr inbounds nuw { i1, i32, i32 }, ptr %.loc17_46.1.temp, i32 0, i32 0, !dbg !13
Instruction does not dominate all uses!
%.loc17_46.1.temp = alloca { i1, i32, i32 }, align 8, !dbg !13
%tuple.elem1.loc17_46.2.tuple.elem = getelementptr inbounds nuw { i1, i32, i32 }, ptr %.loc17_46.1.temp, i32 0, i32 1, !dbg !13
Instruction does not dominate all uses!
%.loc17_46.1.temp = alloca { i1, i32, i32 }, align 8, !dbg !13
%tuple.elem2.loc17_46.2.tuple.elem = getelementptr inbounds nuw { i1, i32, i32 }, ptr %.loc17_46.1.temp, i32 0, i32 2, !dbg !13
```
Adds a `--llvm-verifier` flag to be able to turn this off easily,
particularly for debugging the LLVM IR.
The call workaround is due to a verifier requirement `inlinable function
call in a function with debug info must have a !dbg location`. It
specifically comes up for the `++x` case, with `%1 = call i32
@"_CConvert.8b3d5d6a6c17be04:ImplicitAs.Core.b88d1103f417c6d4"(i32
%other)`. I think #5397 is in the direction of a fix for that, but #5397
was set aside because it puts the debug info in too many places.
Instead, address this by adding a stub location for calls that don't
have a good location. I'm deliberately putting this next to the TODO so
that it's easier to understand the association.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
Factor out the logic for mapping from a `LocId` into a diagnostic
location from check into sem_ir so it can be reused by lowering. Include
the function and instruction being lowered in the pretty stack trace.
Example stack trace:
```carbon
2. filename: examples/sieve.carbon
3. core/prelude/types/int.carbon:213:3: lowering function Core.Op(Core.IntLiteral as Core.ImplicitAs(i32))
fn Op[addr self: Self*](other: Self) = "int.sadd_assign";
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4. core/prelude/operators/arithmetic.carbon:22:27: lowering call
fn Op[addr self: Self*](other: Other);
^~~~~~~~~~~~
```
Use it to replace most existing modernize-loop-convert lints with
range-based for loops. As requested in review of #5475.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
When lowering a specific function whose generic was defined in a
different file, switch to that other file's `FileContext` and lower the
generic there. Also pass the `FileContext` corresponding to the specific
into the `FunctionContext`, and use that `FileContext` for resolving
requests for constants and types from the specific.
In preparation for lowering information from multiple `SemIR::File`s
into a single `llvm::Module`. The primary purpose of this is to support
lowering a local specific for an imported generic function, where the
instructions for the generic function are in a different file than the
instructions for the specific. See #5475 for a draft PR implementing
that functionality on top of this.
The per-`llvm::Module` state now lives in `Lower::Context`, and
`Lower::FileContext` tracks only the per-`SemIR::File` information.
`Lower::Context` should not mention any `SemIR` IDs that are
file-specific. For now, the C++ lowering and the specific coalescing
logic are kept per-file for simplicity.
David Blaikie
Nicholas Bishop
Chandler Carruth
Richard Smith
Jon Ross-Perkins