cca5e74a58
In many cases, the context that TurboFan's ASTGraphBuilder or subsequent reduction operations attaches to nodes does not need to be that exact context, but rather only needs to be one with the same native context, because it is used internally only to fetch the native context, e.g. for creating and throwing exceptions. This reducer recognizes common cases where the context that is specified for a node can be relaxed to a canonical, less specific one. This relaxed context can either be the enclosing function's context or a specific Module or Script context that is explicitly created within the function. This optimization is especially important for TurboFan-generated code stubs which use context specialization and inlining to generate optimal code. Without context relaxation, many extraneous moves are generated to pass exactly the right context to internal functions like ToNumber and AllocateHeapNumber, which only need the native context. By turning context relaxation on, these moves disappear because all these common internal context uses are unified to the context passed into the stub function, which is typically already in the correct context register and remains there for short stubs. It also eliminates the explicit use of a specialized context constant in the code stub in these cases, which could cause memory leaks. Review URL: https://codereview.chromium.org/1244583003 Cr-Commit-Position: refs/heads/master@{#29763} |
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