On 32-bit systems I64XConvertFXX instructions are compiled to calls to
C functions. The TF node for the function call is already generated in
the wasm compiler, the lowering of the I64 parameter is done in the
Int64Lowering. We use the return value of the C function to determine
whether the conversion should trap or not.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/1775903002

Cr-Commit-Position: refs/heads/master@{#34738}