Reset function context when ending a function in IRBuilder #7081
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When IRBuilder builds an empty non-block scope such as a function body, an if arm, a try block, etc, it needs to produce some expression to represent the empty contents. Previously it produced a nop, but change it to produce an empty block instead. The binary writer and printer have special logic to elide empty blocks, so this produces smaller output. Update J2CLOpts to recognize functions containing empty blocks as trivial to avoid regressing one of its tests.
IRBuilder contains a pointer to the current function that is used to create scratch locals, look up the operand types for returns, etc. This pointer is nullable because IRBuilder can also be used in non-function contexts such as global initializers. Visiting the start of a function sets the function pointer, and after this change visiting the end of a function resets the pointer to null. This avoids potential problems where code outside a function would be able to incorrectly use scratch locals and returns if the IRBuilder had previously been used to build a function. This change requires some adjustments to Outlining, which visits code out of order, so ends up visiting code from inside a function after visiting the end of the function. To support this use case, add a `setFunction` method to IRBuilder that lets the user explicitly control its function context. Also remove the optional function pointer parameter to the IRBuilder constructor since it is less flexible and not used.
kripken
approved these changes
Nov 15, 2024
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IRBuilder contains a pointer to the current function that is used to
create scratch locals, look up the operand types for returns, etc. This
pointer is nullable because IRBuilder can also be used in non-function
contexts such as global initializers. Visiting the start of a function
sets the function pointer, and after this change visiting the end of a
function resets the pointer to null. This avoids potential problems
where code outside a function would be able to incorrectly use scratch
locals and returns if the IRBuilder had previously been used to build a
function.
This change requires some adjustments to Outlining, which visits code
out of order, so ends up visiting code from inside a function after
visiting the end of the function. To support this use case, add a
setFunctionmethod to IRBuilder that lets the user explicitly controlits function context. Also remove the optional function pointer
parameter to the IRBuilder constructor since it is less flexible and not
used.