Implements a backend targeting RV32GC and RV64GC, based on Linux standardizing around GC. The assembler is written to make it easy to disable usage of C, but because the sizes of some instruction sequences are compile-time constants, an additional build configuration would need to be defined to make use of it.
The assembler and disassembler cover every RV32/64GC instruction. The simulator covers all instructions except accessing CSRs and the floating point state accessible through such, include accrued exceptions and dynamic rounding mode.
Quirks:
- RISC-V is a compare-and-branch architecture, but some existing "architecture-independent" parts of the Dart compiler assume a condition code architecture. To avoid rewriting these parts, we use a peephole in the assembler to map to compare-and-branch. See Assembler::BranchIf. Luckily nothing depended on taking multiple branches on the same condition code set.
- There are no hardware overflow checks, so we must use Hacker's Delight style software checks. Often these are very cheap: if the sign of one operand is known, a single branch is needed.
- The ranges of RISC-V branches and jumps are such that we use 3 levels of generation for forward branches, instead of the 2 levels of near and far branches used on ARM[64]. Nearly all code is handled by the first two levels with 20-bits of range, with enormous regex matchers triggering the third level that uses aupic+jalr to get 32-bits of range.
- For PC-relative calls in AOT, we always generate auipc+jalr pairs with 32-bits of range, so we never generate trampolines.
- Only a subset of registers are available in some compressed instructions, so we assign the most popular uses to these registers. In particular, THR, TMP[2], CODE and PP. This has the effect of assigning CODE and PP to volatile registers in the C calling convention, whereas they are assigned preserved registers on the other architectures. As on ARM64, PP is untagged; this is so short indices can be accessed with a compressed instruction.
- There are no push or pop instructions, so combining pushes and pops is preferred so we can update SP once.
- The C calling convention has a strongly aligned stack, but unlike on ARM64 we don't need to use an alternate stack pointer. The author ensured language was added to the RISC-V psABI making the OS responsible for realigning the stack pointer for signal handlers, allowing Dart to leave the stack pointer misaligned from the C calling convention's point of view until a foreign call.
- We don't bother with the link register tracking done on ARM[64]. Instead we make use of an alternate link register to avoid inline spilling in the write barrier.
Unimplemented:
- non-trivial FFI cases
- Compressed pointers - No intention to implement.
- Unboxed SIMD - We might make use of the V extension registers when the V extension is ratified.
- BigInt intrinsics
TEST=existing tests for IL level, new tests for assembler/disassembler/simulator
Bug: https://github.com/dart-lang/sdk/issues/38587
Bug: https://github.com/dart-lang/sdk/issues/48164
Change-Id: I991d1df4be5bf55efec5371b767b332d37dfa3e0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/217289
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>
This relands https://dart-review.googlesource.com/c/sdk/+/205633
but without renaming TARGET_OS_IPHONE to DART_TARGET_OS_IPHONE.
It also changes uses of TARGET_OS_IOS to
DART_TARGET_OS_MACOS_IOS to be consistent with the rest of the
VM.
TargetConditionals.h for XCode 13 defines several
TARGET_OS_* preprocessor symbols that confuse the
Dart build. There is probably a more targeted fix
for this, but renaming the symbols that Dart uses
will also prevent this problem if more symbols
are added to the platform headers in the future.
See: https://github.com/dart-lang/sdk/issues/46499
TEST=It builds.
Change-Id: Ie775c19dd23cfdf5f65e5ebc6ee4ec3a561676fa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/205860
Commit-Queue: Zach Anderson <zra@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>
TargetConditionals.h for XCode 13 defines several
TARGET_OS_* preprocessor symbols that confuse the
Dart build. There is probably a more targeted fix
for this, but renaming the symbols that Dart uses
will also prevent this problem if more symbols
are added to the platform headers in the future.
See: https://github.com/dart-lang/sdk/issues/46499
TEST=It builds.
Change-Id: I3b33a03b4a9a14b76d55fe12f8cdefec4b3c3664
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/205633
Commit-Queue: Zach Anderson <zra@google.com>
Reviewed-by: Siva Annamalai <asiva@google.com>
We were mixing and matching `TARGET_OS_IOS` and `TARGET_OS_MACOS_IOS`.
The former is defined by Xcode and not by our own defines leading us to
not actually unit test the iOS calling convention.
The expectation files now properly expect the arguments to be not
word-aligned on the stack.
Issue: https://github.com/dart-lang/sdk/issues/44230
TEST=runtime/vm/compiler/ffi/native_calling_convention_test.cc
(run by vm-precomp-ffi-qemu-linux-release-arm-try)
Change-Id: If982c8cd2625bdb78ed770a9bc3c3061c7b95ede
Cq-Include-Trybots: luci.dart.try:vm-precomp-ffi-qemu-linux-release-arm-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/172560
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Clement Skau <cskau@google.com>
This CL introduces unit tests for the Native* classes in compiler/ffi
that can run for all supported target ABIs on any host architecture.
The unit tests are compiled for all target ABIs with
`tools/build.py run_ffi_unit_tests` and run for all target ABIs with
`tools/test.py ffi_unit`.
The unit test and tested code do not conceptually depend on having a
DartVM. The tests are compiled with a custom `dart::Zone` and
`platform/`. This enables compiling for all `TARGET_ARCH_*` and
`TARGET_OS_*` on any host, and running unit tests for all target ABIs
on any host.
Because the `run_ffi_unit_tests` executables do not include the DartVM
their build is quick (<10seconds) and they are small (~6MB) when
compared to `run_vm_tests` (~250MB).
The tests are added to the existing FFI QEMU bot to prevent adding an
extra bot which would add checkout overhead.
The unit tests themselves are set up to be fairly similar to vm/cc
tests. The only difference is the NativeCallingConvention tests which
are set up with `.expect` files for easy inspection and updating.
TEST=runtime/vm/compiler/ffi/native_calling_convention_test.cc
TEST=runtime/vm/compiler/ffi/native_location_test.cc
TEST=runtime/vm/compiler/ffi/native_type_test.cc
Change-Id: I7b8bf4de9ef070e7546472217e571a60362b9639
Cq-Include-Trybots: luci.dart.try:vm-precomp-ffi-qemu-linux-release-arm-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/171725
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Clement Skau <cskau@google.com>
Reviewed-by: Alexander Thomas <athom@google.com>
Ryan Macnak