Stephen Adams
066962ff60
Change how `@pragma('vm:unsafe:no-bounds-checks')` works.
Instead of never inserting the bounds check, the bounds check is added to the flow graph with a flag that it should later be removed, `omit_check`. The removal occurs in `RangeAnalysis::EliminateRedundantBoundsChecks`. This ensures that the indexed load is pinned by the check, preventing illegal code motion.
`@pragma('vm:unsafe:no-bounds-checks')` is not a mechanism to allow unsafe access. It means that the access is known to be safe because of invariants not apparent to the compiler. Keeping the bounds check in the flow graph allows range analysis to learn from the bounds constraints and perhaps remove other checks. A test was added for this scenario. I didn't see this in the wild, but I did see one case where a refined range allowed a boxing to be removed.
Bug: #56808
TEST=BoundsCheckElimination_Pragma_learning, BoundsCheckElimination_Pragma_learning_control
Change-Id: I5b3f4470d6c40c988a8a0ee563c765f4f5f9128b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/389620
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Stephen Adams <sra@google.com>
Dart VM Compilation Pipeline
This folder contains Dart VM compilation pipeline.
Compilation pipeline is mainly responsible for converting AST or Kernel AST into IL flow graphs and then generating native code from IL.
It has the following structure:
| Directory | What goes there |
|---|---|
assembler/ |
Assemblers and disassemblers |
backend/ |
IL based compilation backend: optimization passes and architecture specific code generation rules |
frontend/ |
Frontends responsible for converting AST into IL |
jit/ |
JIT specific passes and compilation pipeline entry points |
aot/ |
AOT specific passes and compilation pipeline entry points |
. |
Shared code or code without clear designation. |
Currently there are no layering restrictions and components from different subfolders can reference each other.