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Make br_if return the value of its value operand.#539

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sunfishcode wants to merge 1 commit intomasterfrom
br_if-result
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Make br_if return the value of its value operand.#539
sunfishcode wants to merge 1 commit intomasterfrom
br_if-result

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@sunfishcode
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This follows naturally from br_if's value operand being strict. We
evaluate the expression to produce a value even when the condition is
false, so it'd be nice to be able to use the value when the condition
is false too.

This change also makes sense from a low-level compiler perspective. The
value operand of a br_if represents a value "live out" of the br_if's
basic block. Since br_if is a simple conditional branch, the value
should be "live in" in both succesors.

This follows naturally from br_if's value operand being strict. We
evaluate the expression to produce a value even when the condition is
false, so it'd be nice to be able to use the value when the condition
is false too.

This change also makes sense from a low-level compiler perspective. The
value operand of a br_if represents a value "live out" of the br_if's
basic block. Since br_if is a simple conditional branch, the value
should be "live in" in both succesors.
@sunfishcode
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WebAssembly/spec#237 is a PR to the spec repo implementing this, which has the specific proposal for how to do the type checking.

@ghost ghost mentioned this pull request Feb 9, 2016
@sunfishcode
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Closing, as the spec PR is now closed.

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