Compiling LOOKUPSWITCH is complicated, and this op hurts JIT performance more than it helps: * IonMonkey compiles LOOKUPSWITCH and CONDSWITCH to the same MIR. Handling these ops adds a lot of complexity to IonBuilder. * JM(+TI) always stubs LOOKUPSWITCH and usually spends a lot of time in FindNativeCode. Without LOOKUPSWITCH we'd use CONDSWITCH/CASE/DEFAULT and in many cases these are faster because they can avoid stub calls. * Efficiently compiling LOOKUPSWITCH in the new baseline compiler is also not trivial, especially compared to CONDSWITCH/CASE which can just use the existing equality IC.

18 files changed, 68 insertions(+), 722 deletions(-)

Comment on attachment 697110 [details] [diff] [review] Remove JSOP_LOOKUPSWITCH Review of attachment 697110 [details] [diff] [review]: ----------------------------------------------------------------- Nice!

https://hg.mozilla.org/integration/mozilla-inbound/rev/c0e7cc40f356 Try: https://tbpl.mozilla.org/?tree=Try&rev=4c8bc694ada0