[5.2] Add workaround for stack overflow in tree visitation when having a reduced stack size #208
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…duced stack size To determine the correct specific visitation function for a syntax node, we need to switch through a huge switch statement that covers all syntax types. In debug builds, the cases of this switch statement do not share stack space (rdar://55929175). Because of this, the switch statement requires allocates about 15KB of stack space. In scenarios with reduced stack size (in particular dispatch queues), this often results in a stack overflow during syntax tree visitation. To circumvent this problem, this commit moves adds a flag that moves the retrieval of the specific visitation function to its own function. This way, the stack frame that determines the correct visitiation function will be popped of the stack before the function is being called, making the switch's stack space transient instead of having it linger in the call stack. The workaround currently has a 50% performance decrease in release builds, so it is only used in debug builds.
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Rewrite and fix `OneVariableDeclarationPerLine`.
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Cherry-pick of #205
To determine the correct specific visitation function for a syntax node,
we need to switch through a huge switch statement that covers all syntax
types. In debug builds, the cases of this switch statement do not share
stack space (rdar://55929175). Because of this, the switch statement
requires allocates about 15KB of stack space. In scenarios with reduced
stack size (in particular dispatch queues), this often results in a
stack overflow during syntax tree visitation.
To circumvent this problem, this commit moves adds a flag that moves the
retrieval of the specific visitation function to its own function. This
way, the stack frame that determines the correct visitiation function
will be popped of the stack before the function is being called, making
the switch's stack space transient instead of having it linger in the
call stack.
The workaround currently has a 50% performance decrease in release
builds, so it is only used in debug builds.