1. 16 Oct, 2017 1 commit
  2. 28 Sep, 2017 1 commit
    • Enrico Bacis's avatar
      [wasm] Introduce the WasmContext · 6cd7a5a7
      Enrico Bacis authored
      The WasmContext struct introduced in this CL is used to store the
      mem_size and mem_start address of the wasm memory. These variables can
      be accessed at C++ level at graph build time (e.g., initialized during
      instance building). When the GrowMemory runtime is invoked, the context
      variables can be changed in the WasmContext at C++ level so that the
      generated code will load the correct values.
      
      This requires to insert a relocatable pointer only in the
      JSToWasmWrapper (and in the other wasm entry points), the value is then
      passed from function to function as an automatically added additional
      parameter. The WasmContext is then dropped when creating an Interpreter
      Entry or when invoking a JavaScript function. This removes the need of
      patching the generated code at runtime (i.e., when the memory grows)
      with respect to WASM_MEMORY_REFERENCE and WASM_MEMORY_SIZE_REFERENCE.
      However, we still need to patch the code at instance build time to patch
      the JSToWasmWrappers; in fact the address of the WasmContext is not
      known during compilation, but only when the instance is built.
      
      The WasmContext address is passed as the first parameter. This has the
      advantage of not having to move the WasmContext around if the function
      does not use many registers. This CL also changes the wasm calling
      convention so that the first parameter register is different from the
      return value register. The WasmContext is attached to every
      WasmMemoryObject, to share the same context with multiple instances
      sharing the same memory. Moreover, the nodes representing the
      WasmContext variables are cached in the SSA environment, similarly to
      other local variables that might change during execution.  The nodes are
      created when initializing the SSA environment and refreshed every time a
      grow_memory or a function call happens, so that we are sure that they
      always represent the correct mem_size and mem_start variables.
      
      This CL also removes the WasmMemorySize runtime (since it's now possible
      to directly retrieve mem_size from the context) and simplifies the
      GrowMemory runtime (since every instance now has a memory_object).
      
      R=ahaas@chromium.org,clemensh@chromium.org
      CC=gdeepti@chromium.org
      
      Change-Id: I3f058e641284f5a1bbbfc35a64c88da6ff08e240
      Reviewed-on: https://chromium-review.googlesource.com/671008
      Commit-Queue: Enrico Bacis <enricobacis@google.com>
      Reviewed-by: 's avatarClemens Hammacher <clemensh@chromium.org>
      Reviewed-by: 's avatarAndreas Haas <ahaas@chromium.org>
      Cr-Commit-Position: refs/heads/master@{#48209}
      6cd7a5a7
  3. 30 Aug, 2017 1 commit